- Email: [email protected]
The effect of time pressure on risky choice behavior
Acta Psychologica @North-Holland
47 (1981) 89-104 Publishing Company
THE EFFECT OF TIME PRESSURE
ON RISKY CHOICE BEHAVIOR
*
Hasida BEN ZUR and Shlomo J. BREZNITZ University of Haifa, Mount Camel, Received
February
Haifa, Israel
1980
Thirty six subjects chose individually between pairs of gambles under three time pressure conditions: High (8 seconds), Medium (16 seconds) and Low (32 seconds). The gambles in each pair were equated for expected value but differed in variance, amounts to win and lose and their respective probabilities. Information about each dimension could be obtained by the subject sequentially according to his preference. The results show that subjects are less risky under High as compared to Medium and Low time pressure, risk taking being measured by choices of gambles with lower variance or lower amounts to lose and win. Subjects tended to spend more time observing the negative dimensions (amount to lose and probability of losing), whereas under low time pressure they preferred observing their positive counterparts. Information preference was found to be related to choices. Filtration of information and acceleration of its processing appear to be the strategies of coping with time pressure.
Introduction Various situations in everyday life as well as during crises, require making decisions while pressed by deadlines. The process of solving a single decision problem was described as consisting of several stages: perceiving the existence of the decision problem, acquiring information about choice alternatives, searching for alternative possibilities and evaluating this information (Festinger 1964; Janis 1974). Time pressure in this context can be defined in terms of the amount of information that has to be considered and processed during one time unit or in terms of the time allotted for processing a fixed amount of informa* This article is based on the fist author’s Master of Arts thesis supervised by Prof. S. Breznitz and Prof. A. Rapoport and submitted to the Department of Psychology, University of Haifa, Israel, 1977. The research was supported by the National Israeli Academy for Sciences and the Faculty of Social Sciences and Mathematics, University of Haifa. We would like to thank Prof. A. Rapoport for his careful review of an earlier draft of this paper. Thanks are due to Mr. A. Papo, Mrs. D. Bonin and Mrs. R. Maos for their help in the various stages of the research. Requests for reprints should be sent to Mrs. H. Benzur, Ray D. Wolfe Centre for Study of Psychological Stress, University of Haifa, Haifa, Israel. 89
90
H. Ben Zur, S.J. Breznitz / The effect of time pressure
tion. The issue to be elaborated here is how time pressure affects information processing and decision. It has been argued (George 1974) that a decision problem is a stressful condition since it entails a conflict and a threat of negative consequences. In addition, coping with lack of knowledge about choice alternatives or inability to process all available information can cause cognitive strain in addition to the emotional stress. Time pressure may increase this psychological stress because of awareness of unavoidability and a stronger sense of failure emanating from perceived inadequacy in processing and weighting information. Time pressure may also induce feelings of helplessness since the required fast processing is likely to cause disregarding certain informational items which are perceived to be important to the decision maker (DM). Following Miller (1960), three major ways of coping with a situation of unavoidable and time-pressed situations can be postulated. The first is Acceleration, i.e. processing all information at a faster rate. Such activity under restricting conditions may cause errors due to temporary overload of memory, or of the processing capacity. An entirely different means of coping is Avoidance of the decision. On unavoidable decision problems this may express itself in random choices or in choosing according to a momentary standing-out characteristic of choice alternatives. Filtration can be viewed as a compromise strategy, choosing only the subjectively important data for consideration. Such mechanism actually reduces time pressure and enables the DM to decide in a relatively consistent and organized way. This coping mechanism is more likely to be used when the threat of possible negative outcomes is stronger than the threat of not considering all informational items. In the context of decision making under certainty, time pressure was found to enhance avoidance of expected pain (Breznitz 1974), to cause attribution of more weight to negative information in purchase options (Wright 1974), and to lead to conservative votings in state legislations (Hanson et al. 1974). On the basis of the former two experiments’ results it can be suggested that time pressure tends to emphasize the negative aspects of the decision problem. Such emphasis could be achieved by a Filtration mechanism favoring negative information, in an attempt to reduce threat of future negative consequences. The above mentioned research dealt with decisions the results of which were defined as certain. Much research effort aimed at investi-
H. Ben Zur, S.J. Breznitz / The effect of time pressure
91
gating decision making under risk, and there is a controversy concerning the concept of risk and its significance in choices between gambles (Payne 1973). According to an approach which describes a gamble as a probability distribution over monetary values risk is assumed to be reflected by the variance or skewness of that distribution (Lichtenstein 1965; Slavic 1964) or as linear combination of expected value and variance (Pollatsek and Tversky 1970). A different approach characterizes a gamble by the four basic risk dimensions, i.e. the amounts to win and lose and probabilities of winning and losing (Slavic and Licthenstein 1968). These dimensions are assumed to be weighted according to their importance to the DM and to be combined linearly so that the gamble with the higher value is chosen; hence risk would be reflected in assigning more weight to the negative dimensions. Some empirical research has shown that in ratings of risk, probability of losing is assigned the greatest weight (Slavic 1967; Payne 1975). Other research results, however, suggest that ratings do not necessarily reflect choices and_ that amounts to win and lose are more important when choices have real consequences (Lichtenstein 1965; Slavic 1969; Slavic and Lichtenstein 1968). The present research aimed at investigating the effect of time pressure on risk-taking in choices between gambles with monetary consequences. Risk was defined in terms of the variance of a gamble, or, correspondingly, in terms of amounts to win and lose. It was hypothesized that under time pressure the DM would take lesser risks, and such tendency would be reflected in choosing the gamble with lower variance or lower amount to lose. In order to investigate information processing, a new method was used by which the DM chooses for himself informational items relevant to choice alternatives. This method is in certain ways similar to that of Payne (1976) but the system of presentation enabled us to obtain more extensive and more accurate data recording, as in recently published work of Payne and Braunstein (1978). Thus, an attempt was made to investigate some of the processes occurring prior to decision and their relation to final choice. The experiment Method Subjects
Thirty
six first year psychology
students
participated
in the experiment
as part of
92
H. Ben Zur, S. J. Breznitz / The effect of time pressure
their course requirement studies. They were promised a sum of money for playing gambles. The sample included 27 females and 9 males of 20-48 years of age. Apparatus
A display board divided into 12 squares in a 3 X 4 arrangement was constructed. In front of the display board was fixed a set of 12 buttons arranged in a 3 X 4 fashion corresponding to the squares. Behind each square a small lamp was mounted which was lighted by pressing the appropriate button. A transparent paper including information items covered by an opaque white sheet was put on the display board. When a button was pressed the corresponding square was lighted and the information displayed at that location could be seen. Two additional buttons were fixed in front of the apparatus for marking choice. The apparatus was connected to a timer type Digitec-8130 and a printer of the type Digitec-6110. Pressing a button caused the appropriate square to be lighted until the next press, duration of exposure and position of square being automatically printed. Duration was registered in milliseconds with an error of t3 msec. Stimuli
Thirty six pairs of gambles were prepared. Each gamble was characterized by the amounts to win and lose, and the probabilities of winning and losing. The sum of the probabilities was a constant equal or smaller than one. This was done in order to somewhat reduce prediction of one probability from its counterpart. The sum of the two probabilities was always identical in the two gambles constituting a pair so that it would not be a factor in evaluating gambles. Six sums of probabilities of winning and losing were chosen: 1.00, 0.95, 0.85, 0.80, 0.75, and 0.65, and for each sum three different combinations of probabilities were chosen. Two values of expected value (+25 and -25) and two values of variance (90 000 and 5625) were chosen. For each combination of probabilities the amounts to win and lose were determined for a given expected value, one for the lower and one for the higher variance. In this method, for each sum of probabilities six pairs of gambles were constructed so that the gambles in each pair were identical in expected value but differed on variance and on the four risk dimensions. In half of the pairs the gamble with the lower variance was also the one with the lower probability of losing and the opposite was true for the other half. Table 1 presents the 36 pairs of gambles which were used in the experiment. Table 2 presents the correlations between amounts to win and lose and probabilities of winning and losing (AW, AL, PW and PL, correspondingly) over the 72 gambles. The absolute value of AL was used in the computations. As can be seen in table 2, the lowest correlation found is between AW and AL, while the highest correlation is between PW and PL. The correlation between PW and PL, however, is less than 1. The values of the four dimensions were written on a transparent paper using Alfac numbers of 10 mm size. The values of one gamble were written on the right, vertically, and the values of the second gamble were written in parallel to the first, in the middle of the page. The vertical order of dimensions on the page was changed 12 times so that out of 36 pairs of gambles three were presented in the same order
H. Ben Zur, S.J. Breznitz / The effect of time pressure
93
Table 1 The 36 pairs of gambles used in the experiment. EV
Pair
AW
PW
PL
AL
Variance
-25
1
+105 +307 +30 +495 +58 +195 +495 +58 +195 +105 +307 +30 +318 +154 i-541 +65 +186 +98 +98 t.541 +154 +186 +65 +318 +277 +23 +411 +47 +181 +80 +47 +181 +80 +271 +23 +411 +96 +411 +174 +291 +125 +612 +291 +125 +612 +96
0.25 0.45 0.65 0.25 0.45 0.65 0.25 0.45 0.65 0.25 0.45 0.65 0.50 0.25 0.25 0.75 0.75 0.50 0.50 0.25 0.25 0.75 0.75 0.50 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.50 0.35 0.20 0.50 0.35 0.20 0.50 0.35 0.20 0.50
0.75 0.55 0.35 0.75 0.55 0.35 0.75 0.55 0.35 0.75 0.55 0.35 0.45 0.70 0.70 0.20 0.20 0.45 0.45 0.70 0.70 0.20 0.20 0.45 0.40 0.25 0.55 0.40 0.25 0.55 0.40 0.25 0.55 0.40 0.25 0.55 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30
-68 -296 -127 -198 -93 -434 -198 -93 -434 -68 -296 -127 -298 -20 -158 -122 -570 -54 -54 -158 -20 -570 -122 -298 -314 -154 -270 -116 -533 -89 -116 -533 -89 -374 -154 -270 -76 -264 -16 -401 -42 -162 -401 -42 -162 -76
5 9 5 9 5 9 9 5 9 5 9 5 9 5 9 5 9 5 5 9 5 9 5 9 9 5 9 5 9 5 5 9 5 9 5 9 5 9 5 9 5 9 9 5 9 5
2 3 4 5 6 +25
I 8 9 10 11 12
-25
13 14 15 16 17 18
+25
19 20 21 22 23
H. Ben Zur, S.J. Breznitz / The effect of time pressure
94
Table 1 (continued) EV
-25
Pair
AW
PW
PL
AL
Variance
24
+411 +174 +140 +46 +542 +9 +291 +108 +9 +291 +108 +140 +46 +542 +98 +508 +153 +382 +122 +286 +286 +153 +508 +122 +382 +98
0.35 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.45 0.25 0.25 0.35 0.35 0.45 0.45 0.25 0.25 0.35 0.35 0.45
0.45 0.60 0.15 0.35 0.55 0.15 0.35 0.55 0.15 0.35 0.55 0.15 0.35 0.55 0.20 0.40 0.40 0.30 0.30 0.20 0.20 0.40 0.40 0.30 0.30 0.20
-264 -16 -125 -124 -242 -203 -404 -85 -203 -404 -85 -725 -124 -242 -97 -256 -32 -362 -59 -519 -519 -32 -256 -59 -362 -97
9 5 9 5 9 5 9 5 5 9 5 9 5 9 5 9 5 9 5 9 9 5 9 5 9 5
25 26 27 28 29 30
+25
31 32 33 34 35 36
of dimensions. Out of 24 possible arrangements of dimensions 12 were chosen in which there was spatial contingency between amounts or probabilities or an amount and its corresponding probability. This was done in order to minimize mistakes while choosing information for observation. This change in dimensions arrangement prevented salience due to spatial order. Over the 12 arrangements each
Table 2 Correlations
between
the four basic risk dimensions.
Risk dimensions
AW
AL
PW
AL PW PL
+0.27 -0.49 +0.40
_ +0.45 -0.47
_ _ -0.74
H. Ben Zur, S.J. Breznitz / The effect of time pressure
95
dimension appeared an equal number of times in each spatial position. Gambles were randomly chosen for presentation according to the spatial arrangements. The pairs were arranged in such a way that the gamble with the higher variance was on the right in half the pairs and on the left in the other half. The information about location of dimensions was written on the white opaque covering sheet. ‘Thus, the S knew where each informational item was located without knowing its numerical value. When the appropriate button was pressed, the square was lighted and the numerical value appeared. Design
A repeated measures design was employed. For time pressure manipulation three time values were chosen: 8 set (High), 16 set (Medium), and 32 set (Low). 12 pairs of gambles were randomly selected for presentation in each time pressure condition with the following constraints: (a) in each condition out of 12 pairs the gamble with the higher variance appeared six times on the left and six times on the right side of the pair; (b) in each condition there was an equal representation of all probability sums; and (c) in each condition all 12 possible arrangements of dimensions appeared. The 36 pairs of gambles, assigned to time pressure conditions, were divided into three blocks. In each block of 12 gambles four pairs were presented in each time pressure condition, randomly distributed in the block. Order of block presentation and time pressure conditions for different Ss was determined by a Latin Square design. There were six possible combinations of blocks, and each gamble could be presented for 8, 16 or 32 sec. Presentation times were determined in the following manner: if for a given S pairs 1, 2, 3 were presented for 8, 16 and 32 seconds, correspondingly, then to another S they were presented for 32, 8 and 16 seconds and to another for 8, 16 and 32 seconds. Therefore, 18 possible arrangements of blocks and time pressure conditions were used, each arrangement appearing twice for two different Ss. Prbcedure
Upon arriving to the laboratory the S was given written instructions. The instructions explained the nature of the task, procedure, nature of gambles, method of presentation, and decision consequences. It was emphasized that choice is important since choice and luck would determine how much money was to be gained at the end of the experiment. The S was told that he/she had a sum of 15 Israeli pounds at his/her disposal and that if he/she won, he would be given additional money accordingly;if he/she lost, the money would be substracted from the original sum. The entire experiment consisted of 39 trials, the first three being training trials that were not included in the statistical analysis. Each trial included the following steps: one page including information about one pair of gambles was put on the display board. The S was allowed to observe the spatial order of information for a few seconds (without time constraints), so that he/she knew the location of each dimension, and he/she was then told how much time was allowed for observing the inforinstruction, which was accompanied by the mation. Following a verbai “start”
H. Ben Zur, S.J. Breznitz / The effect of time pressure
96
appearance of a light in the upper left empty square, the S could begin acquiring information by pressing the appropriate buttons, one by one. Observation time over, the light in the display disappeared and a weak auditory signal was a sign for the S to mark his/her decision. Pressing the right or left decision button marked a choice of right or left gamble, respectively. Following decision the experimenter replaced the pair of gambles, determined the next time pressure condition and the whole procedure was repeated. In several cases, during the Medium and Low time pressure conditions Ss stopped observing before time was up. When that happened the S waited till the signal for decision was given. The procedure had been demonstrated to each S three times using 8, 16 and 32 set observation times before the experiment began. Following the sequence of 36 trials the S was asked a few questions about the importance of gamble dimensions and then ten gambles were randomly chosen and played. Playing the gambles was done with a gamble “clock” on which areas corresponding to probabilities were marked and an attached pointer was pushed manually. This was also demonstrated before the experiment began. Following the play the S was paid the sum of money he gained. The entire experiment lasted for approximately one and a half hours. Results
All Ss were tested under the three levels of time pressure which will be designated High (8 set) Medium (16 set) and Low (32 set). In order to check the effect of time pressure on activity level prior to choice two observational measures were used: latency - duration of time between the “start” signal and the pressing of the first button; and (b) average duration - the sum of all durations of observations made, not including start time and last observation, divided by total number of observations made not counting the last one, in each trial. If the S was sensitive to changes in objective time allowed for observing information, we may expect changes in the above measures so that the lower the time pressure the higher the score on each measure. Table 3 presents means of the two measures, the score of each S being the mean over the 12 trials in each time pressure condition. As can be seen in table 3, the F values arrived at by one-way analysis of variance with repeated measures are highly significant. Thus, it is concluded that rate of activity was influenced, as expected, by the time pressure manipulation.
Table 3 Means of activity
measures.
Time pressure
High
Medium
Low
F value
Measure (in sec.) Latency Average duration
0.71 1.14
0.78 1.41
0.87 1.72
34.59 160.71
* p < 0.001 (df = 2/70).
* *
91
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Our main hypothesis states that Ss would be less risky under high time pressure. To test this hypothesis risk taking was measured by the proportion of trials in which the S chose the gamble with the lower variance and, lower amounts to win and lose. In order to check for possible effects on choices of the probabilities themselves, choices of gambles with lower variance were divided into those gambles with lower probability of losing and those with higher probability of losing as compared with the second gamble in the pair. Average proportions of choices (out of 6 trials) in each time pressure condition are presented in table 4. Analysis of variance with repeated measures on time pressure and probability of losing indicates a significant effect for time pressure (F = 6.44, df= 2/70, p < 0.005). No effect was found for probability of losing (F = 1.20) or for the interaction between the two factors (F< 1). Newman-Keuls tests revealed a significant difference between High as compared to Medium or Low time pressure (p < 0.01) but not between Medium and Low. Thus, risk-taking as defined by size of gambles variance is lower under the High time pressure condition, in accordance with our hypothesis. Even though the proportion of choices in the High time pressure condition is around 0.50, this cannot be interpreted as being the outcome of a shift towards random behavior, as will be shown by the results of information processing prior to the decision. Information processing was investigated by analyzing dimensions preference prior to decision and the relations between preferences and choices. Dimension preference was operationally defined as the number of observations made on each dimension (over the two gambles) divided by the total number of observations made during a trial. For example, if S made 3, 4, 2 and 3 observations on AW, AL, PW, PL, correspondingly, during one trial, the proportions for each dimension were 0.25, 0.33, 0.17 and 0.25 correspondingly. Proportions were used in order to partial out individual tendency to use many or just a few observations during a trial. In addition, Ss made fewer observations as time pressure became high (the mean number of observations made was 6.77, 11.20, and 18.22, for High, Medium and Low time pressure, correspondingly), and our purpose was to compare the three conditions. The score for each S was the average of proportions for each dimension
Table 4 Average proportions of choices of gambles with lower variance. Time pressure
High
Medium
Low
x
0.58 0.48 0.53
0.46 0.44 0.45
0.45 0.39 0.42
0.50 0.44
Probability of losing Low High x
98
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Table 5 Correlations between proportions conditions.
Time pressure High-Medium High-Low Medium-Low
of observations for each dimension between the time pressure
Dimension AW AL
PW
PL
0.60 0.68 0.62
0.70 0.54 0.72
0.61 0.63 0.71 /
a)p < 0.05; for all other correlations
0.69 0.41 a) 0.46 p < 0.01.
over the 12 trials in each time pressure condition [ 11. In order to check consistency in dimensions preferences, the preference scores for the four dimensions were correlated, between and within the time pressure conditions. The results are presented in tables 5 and 6,correspondingly. As can be seen in table 5, all correlations are positive and significant. These results suggest a highly consistent behavior within the individual across the time pressure conditions. That is to say, if we assume that under the Low time pressure condition the individual observed dimensions according to his preferences, it seems that he could do the same under the High time pressure condition. Table 6 allows us to compare the correlations of dimensions preferences within time pressure conditions. It should be noted that a negative correlation between dimensions preference shows a rejection of one kind of information while a positive correlation shows an acceptance of both kinds of information. Thus, we can see in table 6 that AW and PW, AL and PL are positively correlated under the High time pressure while no such result is observed under the other conditions. This finding suggests a lowered efficiency in information processing under the High time pressure condition, since the above mentioned dimensions values are correlated (see table 2). Finally, those preferred dimensions also predicted choices to a large extent. Table 7 presents the simple and multiple correlations between proportions and two defined choices: proportion of choices of gambles with lower variance and proportion of choices of gambles with lower probability of losing, for each time pressure condition. The most important results in table 7 are the substantial correlations between proportions of observations and choices in the High time pressure condition (multiple correlations are 0.74 and 0.66). Thus, under this condition Ss chose according
[l] An additional measure, the proportion of time spent in each dimension, was found to correlate highly with proportion of observations and therefore was not included in the analysis. (The range of correlations was 0.97-0.98, 0.78-0.85 and 0.73-0.87, for High, Medium and Low time pressure, correspondingly.)
b, p < 0.05
a) p < 0.01
-0.86 a) +0.44 a) -0.46 a)
+0.02 -0.34 b) -0.72 a) -0.73 a) -0.09
AL
-0.66 +0.58 -0.47 +0.65
Dimension AW AL PW PL
a) p < 0.01
Multiple correlation
Variance-low
Choice
b, p < 0.05
0.74 a)
a) a) a) a)
High
‘Time pressure
0.66 a)
-0.50 a) -0.11 +0.29 +0.36 b,
PL-low
0.18
-0.11 +0.11 0.00 +0.02
Variance-low
Medium
0.54 b,
+0.16 +0.03 +0.48 a) +0.32
PL-low
Table 7 Correlations between proportions of observations for each dimension and choices.
-0.49 a) +0.23 -0.85 a)
PL
AW
PW
AW
AL
Medium
High
Dimension AL PW PL
Time pressure PL
0.52 b,
-0.49 a) +0.18 +0.24 +0.22
Variance-low
Low
-0.12
PW
-0.30 -0.28 -0.70 a)
AW
Low
0.63 a)
-0.41 b) -0.29 +0.51 a) +0.27
PL-low
Table 6 Correlations between proportions of observations for each dimension within time pressure conditions.
-0.51 a) +O.Ol
AL
-0.18
PW
PL
100
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Table 8 Average proportions
of observations made on each dimension.
Time pressure
High
Medium
Low
Dimension AW AL PW PL
0.232 0.258 0.245 0.265
0.258 0.250 0.253 0.239
0.261 0.248 0.252 0.240
to their preferred dimensions, another finding that rejects the possibility of random choices. The effect of time pressure on dimensions preference is shown in table 8 which presents means of proportions of observations made on each time pressure condition. Although the changes are small, analyses of variance with repeated measures on time pressure for each dimension revealed a significant effect for amount to win (F = 3.85, df = 2170, p < 0.05) and for probability of losing (I; = 4.04, df = 2170, p < 0.05). Since there is a dependency between the proportions it cannot be determined which dimension was more affected, but the results suggest a change in preference of positive and negative dimensions as a function of time pressure manipulation in accordance with our hypothesis. Since the changes are of a small magnitude, we chose an additional measure for analysis. The order of observing the various dimensions in each time pressure condition may also be considered as a measure of dimensions preference, or their perceived importance towards decision. Order scores were computed in the following way: for each single trial the dimensions were ordered according to the first order in which S observed them. Thus, a score of 1 was assigned to the firstly observed dimension in one of the gambles, a score of 2 was assigned to the secondly observed dimension and so on to a score of 8 which was assigned to the lastly observed dimension. If a dimension was not observed at all, it was assigned a score of 9. Following the above procedure the median of order scores for each dimension
Table 9 Sums of observation order medians for each dimension. Time pressure
High
Medium
Low
Dimension AW AL PW PL
180.0 182.5 169.5 185.5
139.0 180.0 145.0 183.0
138.5 183.0 141.0 182.0
H. Ben Zur, S.J. Breznitz / The effect of time pressure
101
Table 10 Correlations between proportions of observations and importance ratings. Time pressure
High
Dimension AW AL PW PL
0.63 0.52 0.63 0.62
a)p
< 0.01
a) a) a) a)
Medium
Low
0.60 0.39 0.54 0.45
0.32 0.32 0.34 b) 0.34 b)
a) b, a) a)
b, p < 0.05
(over the two gambles) was calculated over the 12 trials in each time pressure condition. These medians were summed up over the 36 Ss, and the sums are presented in table 9; a smaller sum shows that a dimension was given a priority in observation order and vice versa. The data of table 9 were analyzed by analysis of variance for ranked data (Winer 1971). The differences between time pressure conditions were found to be significant for AW (x*r = 11.73, df = 2, p < 0.01) and for PW (x*r = 8.09, df = 2, p < 0.05). These results match the results of proportions of observations concerning the AW dimension. On the whole, the analysis of information processing prior to decision suggests that the positive and negative dimensions are perceived as less and more important, correspondingly, as time pressure becomes higher. Following the experiment Ss rated the importance of each risk dimension in each time pressure condition on a ‘I-point scale. These ratings were correlated with the proportions of observations made on each risk dimension and the results are presented in table IO. All 12 correlations presented in table 10 are positive and 10 out of the 12 are significant. These results lend support to the assumption that proportions of observations reflect dimensions preference.
Discussion Decision behavior in a choice-between-gambles task was shown to be affected by time pressure. Under the High time pressure condition choices were less risky and tendency for preferring the negative dimensions was also found. These results are in accordance with previous findings dealing with choices made under certainty (Breznitz 1974; Wright 1974). Since time pressure is a stressful1 condition adding to apprehension induced by threat of negative consequences, a less risky
102
H. Ben Zur, S. J. Breznitz / The effect of time pressure
choice could be the immediate available solution for lowering such apprehension, contributing to feelings of safety while under stress. While some such process may occur in any kind of stress, the particular feature of time stress reduces the chances of the immediately available response tendency to be replaced by a different one. Previous experience with success and failure could be another factor under stress. Associations between contributing to “conservatism” unpleasant feelings and chances of losing might during time pressure lead to evaluating the probability of losing as greater than its real value, and consequently influence choices towards the less risky alternative. When there is sufficient time to consider and evaluate information, cognitive strain as well as feelings of inadequate performance diminish. Under such conditions we found a lower activity rate and preference of the positive dimensions. Their prominency was markedly expressed in choosing them as the first informational items to be evaluated. Therefore in addition to the weakening of the processes outlined above, extensive considerations of gains before losses could decrease the impact of the latter, leading to choices of risky alternatives. Three different mechanisms were suggested as possible ways of coping with time pressure: Avoidance, Acceleration and Filtration. In the present context High time pressure did not lead to Avoidance of the decision problem as might have been observed in random information processing and random choices. Activity rate was higher under High time pressure and this reflects Acceleration in situations which demand fast performance. Postexperimental data showed that 90% of our subjects claimed to consider all dimensions under Low time pressure while 75% claimed to consider two dimensions only under the low time pressure, but our data revealed that more than two dimensions were observed under the latter condition. It seems that under time pressure the kind of information which was perceived by the individual as most important was processed first, and then processing was continued until time was up. Although efficiency was somewhat reduced, all data pertaining to individual consistency in dimensions preference suggest that under High time pressure a Filtration mechanism was also operating. Such a combination of Filtration and limited Acceleration can be viewed as the optimal decision making strategy when the DM is confronted with information overload while pressed by deadlines. Finally, the pattern of relations between dimensions preferences and choices across time pressure conditions merits an explanation. Propor-
H. Ben Zur, S.J. Breznitz / The effect of time pressure
103
tions of observations predicted choices in the High and Low conditions but prediction was minimized under the Medium condition, especially when choices of gambles with lower variance were analyzed (see table 7). This U curve characteristic is, in our opinion, the result of differential activity in the three conditions. Under High time pressure the Filtration mechanism acts by choosing the most important dimensions for observation while disregarding others, and processing those chosen dimensions determines choices to a large extent. As time pressure becomes lower, however, all dimensions are observed so that observational measures are less sensitive to the underlying processes which lead to choices. But when time pressure is very low, following first evaluation, there will be sufficient time to reconsider certain dimensions, and such reconsiderations are reflected in repeated observations on those dimensions for further processing. Thus, the method of obtaining information about dimensions according to preferences is of greater significance in analyzing information processing prior to decision when the extreme values of the time pressure continuum are investigated.
References Breznitz, S.J., 1974. Threat and false alarm as determinants of fear and avoidance of pain. Final technical report for U.S. Army Research Institute for the Behavioral and Social Sciences. Festinger, L., 1964. Conflict, decision and dissonance. London: Tavistock Publication. George, A.L., 1974. ‘Adaptation to stress in political decision making: the individual, small group and organizational contexts’. In: G.V. Coelho, P.A. Hamburg and J.E. Adams (eds.), Coping and adaptation. New York: Basic Books. pp. 176-245. Hansson, R.D., J.P. Keating and C. Terry, 1974. The effects of mandatory time limits in the voting booth on liberal-conservative voting patterns. Journal of Applied Social Psychology 4,336-342. Janis, I.L., 1974. ‘Vigilance and decision making in personal crises’. In: G.V. Coelho, P.A. Hamburg and J.E. Adams (eds.), Coping and adaptation. New York: Basic Books. pp. 139175. Lichtenstein, S., 1965. Bases for preferences among three outcome bets. Journal of Experimental Psychology 69,162-169. Miller, J.G., 1960. Information input overload and psychopathology. American Journal of Psychiatry 116,695-704. Payne, J.W., 1973. Alternative approaches to decision making under risk: moments versus risk dimensions. Psychological Bulletin 80,439-453. Payne, J.W., 1975. Relation of perceived risk to preference among gambles. Journal of Experimental Psychology: Human Perception and Performance 104,80-94. Payne, J.W., 1976. Task complexity and contingent processing in decision making: an information search and protocol analysis. Organizational Behavior and Human Performance 16, 366-387.
104
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Payne, J.W. and MC. Braunstein, 1978. Risky choice: an examination of information acquisition behavior. Memory and Cognition 6,554-561. Pollatsek, A. and A. Tversky, 1970. A theory of risk. Journal of Mathematical Psychology 7, 540-553. Slavic, P., 1964. Assessment of risk taking behavior. Psychological Bulletin 61, 220-233. Slavic, P., 1967. The relative influence of probabilities and payoffs upon perceived risk of a gamble. Psychonomic Science 9, 223-224. Slavic, P., 1969. Differential effects of real versus hypothetical payoffs on choices among gambles. Journal of Experimental Psychology 80,4344437. Slavic, P. and S. Lichtenstein, 1968. Relative importance of probabilities and payoffs in risk taking. Journal of Experimental Psychology Monographs 78, no. 3. Winer, B.J., 1971. Statistical principles in experimental design. New York: McGraw-Hill Book Company. Wright, P., 1974. The harassed decision maker: time pressures, distractions and the use of evidence. Journal of Applied Psychology 59,555-561.
47 (1981) 89-104 Publishing Company
THE EFFECT OF TIME PRESSURE
ON RISKY CHOICE BEHAVIOR
*
Hasida BEN ZUR and Shlomo J. BREZNITZ University of Haifa, Mount Camel, Received
February
Haifa, Israel
1980
Thirty six subjects chose individually between pairs of gambles under three time pressure conditions: High (8 seconds), Medium (16 seconds) and Low (32 seconds). The gambles in each pair were equated for expected value but differed in variance, amounts to win and lose and their respective probabilities. Information about each dimension could be obtained by the subject sequentially according to his preference. The results show that subjects are less risky under High as compared to Medium and Low time pressure, risk taking being measured by choices of gambles with lower variance or lower amounts to lose and win. Subjects tended to spend more time observing the negative dimensions (amount to lose and probability of losing), whereas under low time pressure they preferred observing their positive counterparts. Information preference was found to be related to choices. Filtration of information and acceleration of its processing appear to be the strategies of coping with time pressure.
Introduction Various situations in everyday life as well as during crises, require making decisions while pressed by deadlines. The process of solving a single decision problem was described as consisting of several stages: perceiving the existence of the decision problem, acquiring information about choice alternatives, searching for alternative possibilities and evaluating this information (Festinger 1964; Janis 1974). Time pressure in this context can be defined in terms of the amount of information that has to be considered and processed during one time unit or in terms of the time allotted for processing a fixed amount of informa* This article is based on the fist author’s Master of Arts thesis supervised by Prof. S. Breznitz and Prof. A. Rapoport and submitted to the Department of Psychology, University of Haifa, Israel, 1977. The research was supported by the National Israeli Academy for Sciences and the Faculty of Social Sciences and Mathematics, University of Haifa. We would like to thank Prof. A. Rapoport for his careful review of an earlier draft of this paper. Thanks are due to Mr. A. Papo, Mrs. D. Bonin and Mrs. R. Maos for their help in the various stages of the research. Requests for reprints should be sent to Mrs. H. Benzur, Ray D. Wolfe Centre for Study of Psychological Stress, University of Haifa, Haifa, Israel. 89
90
H. Ben Zur, S.J. Breznitz / The effect of time pressure
tion. The issue to be elaborated here is how time pressure affects information processing and decision. It has been argued (George 1974) that a decision problem is a stressful condition since it entails a conflict and a threat of negative consequences. In addition, coping with lack of knowledge about choice alternatives or inability to process all available information can cause cognitive strain in addition to the emotional stress. Time pressure may increase this psychological stress because of awareness of unavoidability and a stronger sense of failure emanating from perceived inadequacy in processing and weighting information. Time pressure may also induce feelings of helplessness since the required fast processing is likely to cause disregarding certain informational items which are perceived to be important to the decision maker (DM). Following Miller (1960), three major ways of coping with a situation of unavoidable and time-pressed situations can be postulated. The first is Acceleration, i.e. processing all information at a faster rate. Such activity under restricting conditions may cause errors due to temporary overload of memory, or of the processing capacity. An entirely different means of coping is Avoidance of the decision. On unavoidable decision problems this may express itself in random choices or in choosing according to a momentary standing-out characteristic of choice alternatives. Filtration can be viewed as a compromise strategy, choosing only the subjectively important data for consideration. Such mechanism actually reduces time pressure and enables the DM to decide in a relatively consistent and organized way. This coping mechanism is more likely to be used when the threat of possible negative outcomes is stronger than the threat of not considering all informational items. In the context of decision making under certainty, time pressure was found to enhance avoidance of expected pain (Breznitz 1974), to cause attribution of more weight to negative information in purchase options (Wright 1974), and to lead to conservative votings in state legislations (Hanson et al. 1974). On the basis of the former two experiments’ results it can be suggested that time pressure tends to emphasize the negative aspects of the decision problem. Such emphasis could be achieved by a Filtration mechanism favoring negative information, in an attempt to reduce threat of future negative consequences. The above mentioned research dealt with decisions the results of which were defined as certain. Much research effort aimed at investi-
H. Ben Zur, S.J. Breznitz / The effect of time pressure
91
gating decision making under risk, and there is a controversy concerning the concept of risk and its significance in choices between gambles (Payne 1973). According to an approach which describes a gamble as a probability distribution over monetary values risk is assumed to be reflected by the variance or skewness of that distribution (Lichtenstein 1965; Slavic 1964) or as linear combination of expected value and variance (Pollatsek and Tversky 1970). A different approach characterizes a gamble by the four basic risk dimensions, i.e. the amounts to win and lose and probabilities of winning and losing (Slavic and Licthenstein 1968). These dimensions are assumed to be weighted according to their importance to the DM and to be combined linearly so that the gamble with the higher value is chosen; hence risk would be reflected in assigning more weight to the negative dimensions. Some empirical research has shown that in ratings of risk, probability of losing is assigned the greatest weight (Slavic 1967; Payne 1975). Other research results, however, suggest that ratings do not necessarily reflect choices and_ that amounts to win and lose are more important when choices have real consequences (Lichtenstein 1965; Slavic 1969; Slavic and Lichtenstein 1968). The present research aimed at investigating the effect of time pressure on risk-taking in choices between gambles with monetary consequences. Risk was defined in terms of the variance of a gamble, or, correspondingly, in terms of amounts to win and lose. It was hypothesized that under time pressure the DM would take lesser risks, and such tendency would be reflected in choosing the gamble with lower variance or lower amount to lose. In order to investigate information processing, a new method was used by which the DM chooses for himself informational items relevant to choice alternatives. This method is in certain ways similar to that of Payne (1976) but the system of presentation enabled us to obtain more extensive and more accurate data recording, as in recently published work of Payne and Braunstein (1978). Thus, an attempt was made to investigate some of the processes occurring prior to decision and their relation to final choice. The experiment Method Subjects
Thirty
six first year psychology
students
participated
in the experiment
as part of
92
H. Ben Zur, S. J. Breznitz / The effect of time pressure
their course requirement studies. They were promised a sum of money for playing gambles. The sample included 27 females and 9 males of 20-48 years of age. Apparatus
A display board divided into 12 squares in a 3 X 4 arrangement was constructed. In front of the display board was fixed a set of 12 buttons arranged in a 3 X 4 fashion corresponding to the squares. Behind each square a small lamp was mounted which was lighted by pressing the appropriate button. A transparent paper including information items covered by an opaque white sheet was put on the display board. When a button was pressed the corresponding square was lighted and the information displayed at that location could be seen. Two additional buttons were fixed in front of the apparatus for marking choice. The apparatus was connected to a timer type Digitec-8130 and a printer of the type Digitec-6110. Pressing a button caused the appropriate square to be lighted until the next press, duration of exposure and position of square being automatically printed. Duration was registered in milliseconds with an error of t3 msec. Stimuli
Thirty six pairs of gambles were prepared. Each gamble was characterized by the amounts to win and lose, and the probabilities of winning and losing. The sum of the probabilities was a constant equal or smaller than one. This was done in order to somewhat reduce prediction of one probability from its counterpart. The sum of the two probabilities was always identical in the two gambles constituting a pair so that it would not be a factor in evaluating gambles. Six sums of probabilities of winning and losing were chosen: 1.00, 0.95, 0.85, 0.80, 0.75, and 0.65, and for each sum three different combinations of probabilities were chosen. Two values of expected value (+25 and -25) and two values of variance (90 000 and 5625) were chosen. For each combination of probabilities the amounts to win and lose were determined for a given expected value, one for the lower and one for the higher variance. In this method, for each sum of probabilities six pairs of gambles were constructed so that the gambles in each pair were identical in expected value but differed on variance and on the four risk dimensions. In half of the pairs the gamble with the lower variance was also the one with the lower probability of losing and the opposite was true for the other half. Table 1 presents the 36 pairs of gambles which were used in the experiment. Table 2 presents the correlations between amounts to win and lose and probabilities of winning and losing (AW, AL, PW and PL, correspondingly) over the 72 gambles. The absolute value of AL was used in the computations. As can be seen in table 2, the lowest correlation found is between AW and AL, while the highest correlation is between PW and PL. The correlation between PW and PL, however, is less than 1. The values of the four dimensions were written on a transparent paper using Alfac numbers of 10 mm size. The values of one gamble were written on the right, vertically, and the values of the second gamble were written in parallel to the first, in the middle of the page. The vertical order of dimensions on the page was changed 12 times so that out of 36 pairs of gambles three were presented in the same order
H. Ben Zur, S.J. Breznitz / The effect of time pressure
93
Table 1 The 36 pairs of gambles used in the experiment. EV
Pair
AW
PW
PL
AL
Variance
-25
1
+105 +307 +30 +495 +58 +195 +495 +58 +195 +105 +307 +30 +318 +154 i-541 +65 +186 +98 +98 t.541 +154 +186 +65 +318 +277 +23 +411 +47 +181 +80 +47 +181 +80 +271 +23 +411 +96 +411 +174 +291 +125 +612 +291 +125 +612 +96
0.25 0.45 0.65 0.25 0.45 0.65 0.25 0.45 0.65 0.25 0.45 0.65 0.50 0.25 0.25 0.75 0.75 0.50 0.50 0.25 0.25 0.75 0.75 0.50 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.50 0.35 0.20 0.50 0.35 0.20 0.50 0.35 0.20 0.50
0.75 0.55 0.35 0.75 0.55 0.35 0.75 0.55 0.35 0.75 0.55 0.35 0.45 0.70 0.70 0.20 0.20 0.45 0.45 0.70 0.70 0.20 0.20 0.45 0.40 0.25 0.55 0.40 0.25 0.55 0.40 0.25 0.55 0.40 0.25 0.55 0.30 0.45 0.60 0.30 0.45 0.60 0.30 0.45 0.60 0.30
-68 -296 -127 -198 -93 -434 -198 -93 -434 -68 -296 -127 -298 -20 -158 -122 -570 -54 -54 -158 -20 -570 -122 -298 -314 -154 -270 -116 -533 -89 -116 -533 -89 -374 -154 -270 -76 -264 -16 -401 -42 -162 -401 -42 -162 -76
5 9 5 9 5 9 9 5 9 5 9 5 9 5 9 5 9 5 5 9 5 9 5 9 9 5 9 5 9 5 5 9 5 9 5 9 5 9 5 9 5 9 9 5 9 5
2 3 4 5 6 +25
I 8 9 10 11 12
-25
13 14 15 16 17 18
+25
19 20 21 22 23
H. Ben Zur, S.J. Breznitz / The effect of time pressure
94
Table 1 (continued) EV
-25
Pair
AW
PW
PL
AL
Variance
24
+411 +174 +140 +46 +542 +9 +291 +108 +9 +291 +108 +140 +46 +542 +98 +508 +153 +382 +122 +286 +286 +153 +508 +122 +382 +98
0.35 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.60 0.40 0.20 0.45 0.25 0.25 0.35 0.35 0.45 0.45 0.25 0.25 0.35 0.35 0.45
0.45 0.60 0.15 0.35 0.55 0.15 0.35 0.55 0.15 0.35 0.55 0.15 0.35 0.55 0.20 0.40 0.40 0.30 0.30 0.20 0.20 0.40 0.40 0.30 0.30 0.20
-264 -16 -125 -124 -242 -203 -404 -85 -203 -404 -85 -725 -124 -242 -97 -256 -32 -362 -59 -519 -519 -32 -256 -59 -362 -97
9 5 9 5 9 5 9 5 5 9 5 9 5 9 5 9 5 9 5 9 9 5 9 5 9 5
25 26 27 28 29 30
+25
31 32 33 34 35 36
of dimensions. Out of 24 possible arrangements of dimensions 12 were chosen in which there was spatial contingency between amounts or probabilities or an amount and its corresponding probability. This was done in order to minimize mistakes while choosing information for observation. This change in dimensions arrangement prevented salience due to spatial order. Over the 12 arrangements each
Table 2 Correlations
between
the four basic risk dimensions.
Risk dimensions
AW
AL
PW
AL PW PL
+0.27 -0.49 +0.40
_ +0.45 -0.47
_ _ -0.74
H. Ben Zur, S.J. Breznitz / The effect of time pressure
95
dimension appeared an equal number of times in each spatial position. Gambles were randomly chosen for presentation according to the spatial arrangements. The pairs were arranged in such a way that the gamble with the higher variance was on the right in half the pairs and on the left in the other half. The information about location of dimensions was written on the white opaque covering sheet. ‘Thus, the S knew where each informational item was located without knowing its numerical value. When the appropriate button was pressed, the square was lighted and the numerical value appeared. Design
A repeated measures design was employed. For time pressure manipulation three time values were chosen: 8 set (High), 16 set (Medium), and 32 set (Low). 12 pairs of gambles were randomly selected for presentation in each time pressure condition with the following constraints: (a) in each condition out of 12 pairs the gamble with the higher variance appeared six times on the left and six times on the right side of the pair; (b) in each condition there was an equal representation of all probability sums; and (c) in each condition all 12 possible arrangements of dimensions appeared. The 36 pairs of gambles, assigned to time pressure conditions, were divided into three blocks. In each block of 12 gambles four pairs were presented in each time pressure condition, randomly distributed in the block. Order of block presentation and time pressure conditions for different Ss was determined by a Latin Square design. There were six possible combinations of blocks, and each gamble could be presented for 8, 16 or 32 sec. Presentation times were determined in the following manner: if for a given S pairs 1, 2, 3 were presented for 8, 16 and 32 seconds, correspondingly, then to another S they were presented for 32, 8 and 16 seconds and to another for 8, 16 and 32 seconds. Therefore, 18 possible arrangements of blocks and time pressure conditions were used, each arrangement appearing twice for two different Ss. Prbcedure
Upon arriving to the laboratory the S was given written instructions. The instructions explained the nature of the task, procedure, nature of gambles, method of presentation, and decision consequences. It was emphasized that choice is important since choice and luck would determine how much money was to be gained at the end of the experiment. The S was told that he/she had a sum of 15 Israeli pounds at his/her disposal and that if he/she won, he would be given additional money accordingly;if he/she lost, the money would be substracted from the original sum. The entire experiment consisted of 39 trials, the first three being training trials that were not included in the statistical analysis. Each trial included the following steps: one page including information about one pair of gambles was put on the display board. The S was allowed to observe the spatial order of information for a few seconds (without time constraints), so that he/she knew the location of each dimension, and he/she was then told how much time was allowed for observing the inforinstruction, which was accompanied by the mation. Following a verbai “start”
H. Ben Zur, S.J. Breznitz / The effect of time pressure
96
appearance of a light in the upper left empty square, the S could begin acquiring information by pressing the appropriate buttons, one by one. Observation time over, the light in the display disappeared and a weak auditory signal was a sign for the S to mark his/her decision. Pressing the right or left decision button marked a choice of right or left gamble, respectively. Following decision the experimenter replaced the pair of gambles, determined the next time pressure condition and the whole procedure was repeated. In several cases, during the Medium and Low time pressure conditions Ss stopped observing before time was up. When that happened the S waited till the signal for decision was given. The procedure had been demonstrated to each S three times using 8, 16 and 32 set observation times before the experiment began. Following the sequence of 36 trials the S was asked a few questions about the importance of gamble dimensions and then ten gambles were randomly chosen and played. Playing the gambles was done with a gamble “clock” on which areas corresponding to probabilities were marked and an attached pointer was pushed manually. This was also demonstrated before the experiment began. Following the play the S was paid the sum of money he gained. The entire experiment lasted for approximately one and a half hours. Results
All Ss were tested under the three levels of time pressure which will be designated High (8 set) Medium (16 set) and Low (32 set). In order to check the effect of time pressure on activity level prior to choice two observational measures were used: latency - duration of time between the “start” signal and the pressing of the first button; and (b) average duration - the sum of all durations of observations made, not including start time and last observation, divided by total number of observations made not counting the last one, in each trial. If the S was sensitive to changes in objective time allowed for observing information, we may expect changes in the above measures so that the lower the time pressure the higher the score on each measure. Table 3 presents means of the two measures, the score of each S being the mean over the 12 trials in each time pressure condition. As can be seen in table 3, the F values arrived at by one-way analysis of variance with repeated measures are highly significant. Thus, it is concluded that rate of activity was influenced, as expected, by the time pressure manipulation.
Table 3 Means of activity
measures.
Time pressure
High
Medium
Low
F value
Measure (in sec.) Latency Average duration
0.71 1.14
0.78 1.41
0.87 1.72
34.59 160.71
* p < 0.001 (df = 2/70).
* *
91
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Our main hypothesis states that Ss would be less risky under high time pressure. To test this hypothesis risk taking was measured by the proportion of trials in which the S chose the gamble with the lower variance and, lower amounts to win and lose. In order to check for possible effects on choices of the probabilities themselves, choices of gambles with lower variance were divided into those gambles with lower probability of losing and those with higher probability of losing as compared with the second gamble in the pair. Average proportions of choices (out of 6 trials) in each time pressure condition are presented in table 4. Analysis of variance with repeated measures on time pressure and probability of losing indicates a significant effect for time pressure (F = 6.44, df= 2/70, p < 0.005). No effect was found for probability of losing (F = 1.20) or for the interaction between the two factors (F< 1). Newman-Keuls tests revealed a significant difference between High as compared to Medium or Low time pressure (p < 0.01) but not between Medium and Low. Thus, risk-taking as defined by size of gambles variance is lower under the High time pressure condition, in accordance with our hypothesis. Even though the proportion of choices in the High time pressure condition is around 0.50, this cannot be interpreted as being the outcome of a shift towards random behavior, as will be shown by the results of information processing prior to the decision. Information processing was investigated by analyzing dimensions preference prior to decision and the relations between preferences and choices. Dimension preference was operationally defined as the number of observations made on each dimension (over the two gambles) divided by the total number of observations made during a trial. For example, if S made 3, 4, 2 and 3 observations on AW, AL, PW, PL, correspondingly, during one trial, the proportions for each dimension were 0.25, 0.33, 0.17 and 0.25 correspondingly. Proportions were used in order to partial out individual tendency to use many or just a few observations during a trial. In addition, Ss made fewer observations as time pressure became high (the mean number of observations made was 6.77, 11.20, and 18.22, for High, Medium and Low time pressure, correspondingly), and our purpose was to compare the three conditions. The score for each S was the average of proportions for each dimension
Table 4 Average proportions of choices of gambles with lower variance. Time pressure
High
Medium
Low
x
0.58 0.48 0.53
0.46 0.44 0.45
0.45 0.39 0.42
0.50 0.44
Probability of losing Low High x
98
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Table 5 Correlations between proportions conditions.
Time pressure High-Medium High-Low Medium-Low
of observations for each dimension between the time pressure
Dimension AW AL
PW
PL
0.60 0.68 0.62
0.70 0.54 0.72
0.61 0.63 0.71 /
a)p < 0.05; for all other correlations
0.69 0.41 a) 0.46 p < 0.01.
over the 12 trials in each time pressure condition [ 11. In order to check consistency in dimensions preferences, the preference scores for the four dimensions were correlated, between and within the time pressure conditions. The results are presented in tables 5 and 6,correspondingly. As can be seen in table 5, all correlations are positive and significant. These results suggest a highly consistent behavior within the individual across the time pressure conditions. That is to say, if we assume that under the Low time pressure condition the individual observed dimensions according to his preferences, it seems that he could do the same under the High time pressure condition. Table 6 allows us to compare the correlations of dimensions preferences within time pressure conditions. It should be noted that a negative correlation between dimensions preference shows a rejection of one kind of information while a positive correlation shows an acceptance of both kinds of information. Thus, we can see in table 6 that AW and PW, AL and PL are positively correlated under the High time pressure while no such result is observed under the other conditions. This finding suggests a lowered efficiency in information processing under the High time pressure condition, since the above mentioned dimensions values are correlated (see table 2). Finally, those preferred dimensions also predicted choices to a large extent. Table 7 presents the simple and multiple correlations between proportions and two defined choices: proportion of choices of gambles with lower variance and proportion of choices of gambles with lower probability of losing, for each time pressure condition. The most important results in table 7 are the substantial correlations between proportions of observations and choices in the High time pressure condition (multiple correlations are 0.74 and 0.66). Thus, under this condition Ss chose according
[l] An additional measure, the proportion of time spent in each dimension, was found to correlate highly with proportion of observations and therefore was not included in the analysis. (The range of correlations was 0.97-0.98, 0.78-0.85 and 0.73-0.87, for High, Medium and Low time pressure, correspondingly.)
b, p < 0.05
a) p < 0.01
-0.86 a) +0.44 a) -0.46 a)
+0.02 -0.34 b) -0.72 a) -0.73 a) -0.09
AL
-0.66 +0.58 -0.47 +0.65
Dimension AW AL PW PL
a) p < 0.01
Multiple correlation
Variance-low
Choice
b, p < 0.05
0.74 a)
a) a) a) a)
High
‘Time pressure
0.66 a)
-0.50 a) -0.11 +0.29 +0.36 b,
PL-low
0.18
-0.11 +0.11 0.00 +0.02
Variance-low
Medium
0.54 b,
+0.16 +0.03 +0.48 a) +0.32
PL-low
Table 7 Correlations between proportions of observations for each dimension and choices.
-0.49 a) +0.23 -0.85 a)
PL
AW
PW
AW
AL
Medium
High
Dimension AL PW PL
Time pressure PL
0.52 b,
-0.49 a) +0.18 +0.24 +0.22
Variance-low
Low
-0.12
PW
-0.30 -0.28 -0.70 a)
AW
Low
0.63 a)
-0.41 b) -0.29 +0.51 a) +0.27
PL-low
Table 6 Correlations between proportions of observations for each dimension within time pressure conditions.
-0.51 a) +O.Ol
AL
-0.18
PW
PL
100
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Table 8 Average proportions
of observations made on each dimension.
Time pressure
High
Medium
Low
Dimension AW AL PW PL
0.232 0.258 0.245 0.265
0.258 0.250 0.253 0.239
0.261 0.248 0.252 0.240
to their preferred dimensions, another finding that rejects the possibility of random choices. The effect of time pressure on dimensions preference is shown in table 8 which presents means of proportions of observations made on each time pressure condition. Although the changes are small, analyses of variance with repeated measures on time pressure for each dimension revealed a significant effect for amount to win (F = 3.85, df = 2170, p < 0.05) and for probability of losing (I; = 4.04, df = 2170, p < 0.05). Since there is a dependency between the proportions it cannot be determined which dimension was more affected, but the results suggest a change in preference of positive and negative dimensions as a function of time pressure manipulation in accordance with our hypothesis. Since the changes are of a small magnitude, we chose an additional measure for analysis. The order of observing the various dimensions in each time pressure condition may also be considered as a measure of dimensions preference, or their perceived importance towards decision. Order scores were computed in the following way: for each single trial the dimensions were ordered according to the first order in which S observed them. Thus, a score of 1 was assigned to the firstly observed dimension in one of the gambles, a score of 2 was assigned to the secondly observed dimension and so on to a score of 8 which was assigned to the lastly observed dimension. If a dimension was not observed at all, it was assigned a score of 9. Following the above procedure the median of order scores for each dimension
Table 9 Sums of observation order medians for each dimension. Time pressure
High
Medium
Low
Dimension AW AL PW PL
180.0 182.5 169.5 185.5
139.0 180.0 145.0 183.0
138.5 183.0 141.0 182.0
H. Ben Zur, S.J. Breznitz / The effect of time pressure
101
Table 10 Correlations between proportions of observations and importance ratings. Time pressure
High
Dimension AW AL PW PL
0.63 0.52 0.63 0.62
a)p
< 0.01
a) a) a) a)
Medium
Low
0.60 0.39 0.54 0.45
0.32 0.32 0.34 b) 0.34 b)
a) b, a) a)
b, p < 0.05
(over the two gambles) was calculated over the 12 trials in each time pressure condition. These medians were summed up over the 36 Ss, and the sums are presented in table 9; a smaller sum shows that a dimension was given a priority in observation order and vice versa. The data of table 9 were analyzed by analysis of variance for ranked data (Winer 1971). The differences between time pressure conditions were found to be significant for AW (x*r = 11.73, df = 2, p < 0.01) and for PW (x*r = 8.09, df = 2, p < 0.05). These results match the results of proportions of observations concerning the AW dimension. On the whole, the analysis of information processing prior to decision suggests that the positive and negative dimensions are perceived as less and more important, correspondingly, as time pressure becomes higher. Following the experiment Ss rated the importance of each risk dimension in each time pressure condition on a ‘I-point scale. These ratings were correlated with the proportions of observations made on each risk dimension and the results are presented in table IO. All 12 correlations presented in table 10 are positive and 10 out of the 12 are significant. These results lend support to the assumption that proportions of observations reflect dimensions preference.
Discussion Decision behavior in a choice-between-gambles task was shown to be affected by time pressure. Under the High time pressure condition choices were less risky and tendency for preferring the negative dimensions was also found. These results are in accordance with previous findings dealing with choices made under certainty (Breznitz 1974; Wright 1974). Since time pressure is a stressful1 condition adding to apprehension induced by threat of negative consequences, a less risky
102
H. Ben Zur, S. J. Breznitz / The effect of time pressure
choice could be the immediate available solution for lowering such apprehension, contributing to feelings of safety while under stress. While some such process may occur in any kind of stress, the particular feature of time stress reduces the chances of the immediately available response tendency to be replaced by a different one. Previous experience with success and failure could be another factor under stress. Associations between contributing to “conservatism” unpleasant feelings and chances of losing might during time pressure lead to evaluating the probability of losing as greater than its real value, and consequently influence choices towards the less risky alternative. When there is sufficient time to consider and evaluate information, cognitive strain as well as feelings of inadequate performance diminish. Under such conditions we found a lower activity rate and preference of the positive dimensions. Their prominency was markedly expressed in choosing them as the first informational items to be evaluated. Therefore in addition to the weakening of the processes outlined above, extensive considerations of gains before losses could decrease the impact of the latter, leading to choices of risky alternatives. Three different mechanisms were suggested as possible ways of coping with time pressure: Avoidance, Acceleration and Filtration. In the present context High time pressure did not lead to Avoidance of the decision problem as might have been observed in random information processing and random choices. Activity rate was higher under High time pressure and this reflects Acceleration in situations which demand fast performance. Postexperimental data showed that 90% of our subjects claimed to consider all dimensions under Low time pressure while 75% claimed to consider two dimensions only under the low time pressure, but our data revealed that more than two dimensions were observed under the latter condition. It seems that under time pressure the kind of information which was perceived by the individual as most important was processed first, and then processing was continued until time was up. Although efficiency was somewhat reduced, all data pertaining to individual consistency in dimensions preference suggest that under High time pressure a Filtration mechanism was also operating. Such a combination of Filtration and limited Acceleration can be viewed as the optimal decision making strategy when the DM is confronted with information overload while pressed by deadlines. Finally, the pattern of relations between dimensions preferences and choices across time pressure conditions merits an explanation. Propor-
H. Ben Zur, S.J. Breznitz / The effect of time pressure
103
tions of observations predicted choices in the High and Low conditions but prediction was minimized under the Medium condition, especially when choices of gambles with lower variance were analyzed (see table 7). This U curve characteristic is, in our opinion, the result of differential activity in the three conditions. Under High time pressure the Filtration mechanism acts by choosing the most important dimensions for observation while disregarding others, and processing those chosen dimensions determines choices to a large extent. As time pressure becomes lower, however, all dimensions are observed so that observational measures are less sensitive to the underlying processes which lead to choices. But when time pressure is very low, following first evaluation, there will be sufficient time to reconsider certain dimensions, and such reconsiderations are reflected in repeated observations on those dimensions for further processing. Thus, the method of obtaining information about dimensions according to preferences is of greater significance in analyzing information processing prior to decision when the extreme values of the time pressure continuum are investigated.
References Breznitz, S.J., 1974. Threat and false alarm as determinants of fear and avoidance of pain. Final technical report for U.S. Army Research Institute for the Behavioral and Social Sciences. Festinger, L., 1964. Conflict, decision and dissonance. London: Tavistock Publication. George, A.L., 1974. ‘Adaptation to stress in political decision making: the individual, small group and organizational contexts’. In: G.V. Coelho, P.A. Hamburg and J.E. Adams (eds.), Coping and adaptation. New York: Basic Books. pp. 176-245. Hansson, R.D., J.P. Keating and C. Terry, 1974. The effects of mandatory time limits in the voting booth on liberal-conservative voting patterns. Journal of Applied Social Psychology 4,336-342. Janis, I.L., 1974. ‘Vigilance and decision making in personal crises’. In: G.V. Coelho, P.A. Hamburg and J.E. Adams (eds.), Coping and adaptation. New York: Basic Books. pp. 139175. Lichtenstein, S., 1965. Bases for preferences among three outcome bets. Journal of Experimental Psychology 69,162-169. Miller, J.G., 1960. Information input overload and psychopathology. American Journal of Psychiatry 116,695-704. Payne, J.W., 1973. Alternative approaches to decision making under risk: moments versus risk dimensions. Psychological Bulletin 80,439-453. Payne, J.W., 1975. Relation of perceived risk to preference among gambles. Journal of Experimental Psychology: Human Perception and Performance 104,80-94. Payne, J.W., 1976. Task complexity and contingent processing in decision making: an information search and protocol analysis. Organizational Behavior and Human Performance 16, 366-387.
104
H. Ben Zur, S.J. Breznitz / The effect of time pressure
Payne, J.W. and MC. Braunstein, 1978. Risky choice: an examination of information acquisition behavior. Memory and Cognition 6,554-561. Pollatsek, A. and A. Tversky, 1970. A theory of risk. Journal of Mathematical Psychology 7, 540-553. Slavic, P., 1964. Assessment of risk taking behavior. Psychological Bulletin 61, 220-233. Slavic, P., 1967. The relative influence of probabilities and payoffs upon perceived risk of a gamble. Psychonomic Science 9, 223-224. Slavic, P., 1969. Differential effects of real versus hypothetical payoffs on choices among gambles. Journal of Experimental Psychology 80,4344437. Slavic, P. and S. Lichtenstein, 1968. Relative importance of probabilities and payoffs in risk taking. Journal of Experimental Psychology Monographs 78, no. 3. Winer, B.J., 1971. Statistical principles in experimental design. New York: McGraw-Hill Book Company. Wright, P., 1974. The harassed decision maker: time pressures, distractions and the use of evidence. Journal of Applied Psychology 59,555-561.