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Personality and the effects of stress on recognition memory
JOURNAL
OF RESEARCH
IN PBRSONALITY
18,
164-178
(1984)
Personality and the Effects of Stress on Recognition Memory ROBERT M. STELMACK, LINDA D. WIELAND,MARY U. WALL, ANDLOUISEPLOUFFE University
of Ottawa
The experiment examined the contribution of anxiety, extraversion, neuroticism, and psychoticism to recognition memory for pictures and words using a signal detection method. Independent groups of subjects performed a recognition memory task under one of four conditions (control, noise, threat, and reward) that was intended to capitalize on dispositions which characterize the personality dimensions. In an ego threat condition involving personal evaluation, introverts displayed a performance decrement relative to noise and reward conditions. Psychoticism was inversely related to performance in the noise and threat conditions and directly related in a reward condition. In general, J. A. Gray’s (1981) model of anxiety and impulsiveness accommodates much of the data, but the mechanisms which mediate the influence of personality on memory performance are not clear.
Eysenck’s typology of personality has recently been subject to important revisions (Eysenck & Eysenck, 1975). Moreover, evidence from psychophysiological and physiological research has prompted new speculations on the biological basis of Eysenck’s personality dimensions. The present study was designed to examine the contribution of personality differences to recognition memory performance in the context of these developments. Eysenck (1967) proposed that individual differences between introverts and extraverts in a wide range of social and psychiatric behaviors may depend on differences in cortical arousal, with introverts characterized by lower thresholds of arousal than extraverts. From this general hypothesis, individual differences between introverts and extraverts have been predicted in a number of experimental paradigms that considered such processes as sensory sensitivity, attention, conditioning, and memory (cf. Eysenck, 1981). During this period, the validity of the arousal hypothesis has been investigated intensively with physiological and psychophysioThis research was supported by the Social Sciences and Humanities Research Council of Canada, Grant 410-77-0833 and by the Natural Science and Engineering Research Council of Canada, Grant A7057. Address requests for reprints to Robert M. Stelmack, School of Psychology, University of Ottawa, Ottawa, Ontario KlN6N5, Canada. 164 0092-6566184 Copyright All rights
$3.00
Q 1984 by Academic Press, Inc. of reproduction in any form reserved.
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logical methods. Consequently, a number of amendments to the basic hypothesis have been proposed. Foremost among these is the schema advocated by Gray (1981), who proposed that anxiety (neurotic introversion) is dependent on mechanisms mediating a behavioral inhibition system which is reflected in differences in sensitivity to punishment or threats of punishment, and that individual differences in impulsiveness depend on an appetitive motivational system which is reflected in differences in susceptibility to reward. At the same time, there have been significant revisions to Eysenck’s typology (Eysenck & Eysenck, 1964) with the development of the Eysenck Personality Questionnaire (EPQ) and the introduction of a psychoticism or tough-mindedness scale (Eysenck & Eysenck, 1975). In this revision, impulsivity items from the extraversion (E) scale have been removed and the psychoticism (P) scale has been shown to correlate positively with impulsiveness measures (Eysenck & Eysenck, 1978). With the emergence of impulsiveness as a central personality construct, it is not clear whether individual variation in memory effects previously attributed to E will be maintained or whether this variation will be attibuted to P. Work in our own laboratory has primarily addressed the arousal hypothesis by examining differences between introverts and extraverts in their response to sensory stimulation (Stelmack, 1981). Evidence from several sources, including psychophysical, electrodermal, and evoked potential measures, indicate that introverts display an enhanced response to sensory stimulation. We have argued elsewhere that these effects may be referred to differences at the level of the sensory nerve (Stelmack & Plouffe, 1983). These findings demonstrate clear differences between introverts and extraverts in stimulus reception and encoding processes; one would expect such differences to be expressed in memory performance. It is from the context of these recent developments that the present study examined the relationship of personality differences to recognition memory performance. Although recent advances in personality theory have not been extensively exploited in the investigation of individual differences in memory, there has been good progress in articulating differences in the operation of memory processes of subjects who differ in degree of anxiety, or E and neuroti+sm (N). The work most extensively reported has extended from the Yerkes-Dodson law where the relationship between anxiety and task difficulty has been explored (cf. Broadhurst, 1959). To a large extent, that research was based on the view that task difficulty, or other stressors such as noise or ego threat, increases arousal and that arousal has interactive effects with memory performance. As expected, high-anxiety subjects have been found to display performance superior to that of low-anxiety subjects on simple paired associate learning tasks, while low-anxiety
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subjects are superior on more difficult tasks (cf. M. W. Eysenck, 1977). These effects, however, have not been consistently observed and the processes that mediate the effects are not well understood (Mueller, 1979). Stress induced by negative feedback or evaluation has also been found to both increase levels of self-reported anxiety in introverts (Freemont, Means, & Means, 1970) and adversely affect memory performance in high-anxiety subjects (Sarason, 1956). In a more recent study, no differences between high- and low-anxiety subjects were observed in a retrieval task where ego threat instructions were applied (Mueller & Wherry, 1982). Overall, however, there has been surprisingly little work investigating the effects of stress on memory for subjects who differ in degree of anxiety, especially in view of the prominence given to susceptibility to stress in current theories of anxiety (Spielberger, 1972). Moreover, it is not clear whether it is the E or N factors, or both, which contribute to the effects of anxiety on memory performance. Recent research suggests that the effects of anxiety on memory are reflected in individual differences in the encoding of semantic and physical characteristics of verbal stimuli. The findings lend themselves to a “levels of processing” interpretation whereby the more elaborate organization or effort which is required for the encoding of semantic features is restricted with high-anxiety subjects. Schwartz (1975, 1979) found that the semantic properties of verbal material, rather than the physical properties, were more readily accessed by introverts than extraverts. Mueller (1979) also reported that high-anxiety subjects encoded fewer semantic features, encoded less elaborately, and were less flexible in their use of alternative memory strategies. Overall, this research indicates that qualitative differences in encoding may be an important focus for explicating the effects of anxiety on memory performance. Recognition memory, with its emphasis on encoding rather than retrieval processes (cf. Mandler, 1980) may be a useful paradigm for examining the encoding effects displayed by anxious subjects in previous research. In the present inquiry, recognition memory for pictures and words of subjects who differ in degree of anxiety, E, N, and P was examined under four stress conditions: noise, threat, reward, and control (no treatment). Employing both verbal and pictorial stimuli exploits the distinction between semantic and physical characteristics that have been implicated in the demonstration of differences in the memory performance of highand low-anxiety subjects. The conditions applied in this study were intended to capitalize on dispositions which are currently thought to characterize the personality dimensions E, N, and P measured by the EPQ. Thus, a noise condition was expected to promote a general increase in arousal which would be reflected in differences in recognition memory performance along the E
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dimension. In this condition, introverts and extraverts, if they are characterized by differences in cortical arousal (Eysenck, 1967) would be differentially influenced, with introverts showing a decrement and extraverts showing an increment relative to their performance in the control condition. With respect to the threat condition, a number of authors maintain that high-anxiety subjects are particularly sensitive to situations of perceived threat to self-esteem (Spielberger, 1972), and Gray (1981) has argued that sensitivity to aversive stimuli is a fundamental determinant of anxiety. If anxiety has deleterious effects on encoding processes as has been suggested, the threat condition should exacerbate those effects. The reward condition was introduced to focus on impulsiveness, a characteristic of the P dimension. Since impulsive subjects are thought to be more susceptible to reward than low impulsives (Gray, 1981), it may be expected that their performance would be influenced, although the dynamics of this process are not clear. One may suppose that impulsive subjects would be inclined to make more false positives in a reward condition which may result in a performance decrement. On the other hand, there is some evidence which indicates that recognition memory performance of high-impulsive subjects is facilitated with increases in arousal (Bowyer. Humphreys, & Revelle, 1983). If the reward condition simply serves to increase arousal or interest, the performance of high-impulsive subjects may be facilitated. In the present study, anxiety has been defined by the State-Trait Anxiety Inventory (STAI) (Spielberger, Gorsuch, & Lushene, 1970). Because the state anxiety measure is situation specific, it has been suggested that it may be more sensitive to the effects of stress on memory performance than trait anxiety which is regarded as an endogenous disposition (M. W. Eysenck, 1979). In addition to P, the EPQ provides independent measures of E and N, both of which correlate with trait anxiety; this allows the contribution of E and N in the effects of anxiety on recognition memory performance to be assessed. METHOD
Subjects Subjects were 120 university and community college students, 80 women and 40 men. The mean age was 23.5 years, SD = 5.41. Subjects performed a recognition memory task under one of four conditions to which they had been randomly assigned: control, noise, threat, or reward. Each condition contained 20 women and 10 men. All subjects were administered the STAI and the EPQ. The means and standard deviations for the personality variables were as follows: trait anxiety, X = 39.01 (SD = 9.62); extraversion, X = 14.05 (SD = 4.77); neuroticism, X = 11.07 (SD = 5.35); and psychoticism, X = 3.11 (SD = 2.42). The four groups did not differ on these personality dimensions (F < 1). Pearson correlations between STAI and EPQ scores for these subjects are shown in Table 1. There was no remarkable departure from this pattern of intercorrelations within each of the four groups.
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CORRELATIONOF PERXINALITY DIMENSIONS(N = 120) STAI
EPQ E -
E N P
N
P
Trait anxiety
-0.13 -
-0.19* 0.16* -
- 0.24** 0.76** 0.26**
* p < .05. ** p < .Ol. Apparatus and Procedure The stimuli were 140 slides of concrete words in pica type and 140 slides of unambiguous line drawings of simple objects (Stehnack, PlouBe, & Winogron, 1983) which were presented by a Kodak carousel projector (Model 800). Half of the items in each category were randomly selected, mixed, and displayed as target stimuli during the acquisition phase of the recognition memory task, and the remainder were employed as distracters during the test phase. The general procedure followed the fixed-interval observation rating experiment described by Egan, Schulman, and Greenberg (1959). Subjects were tested individually or in small groups. After completing the EPQ and the STAI trait anxiety questionnaires, subjects in all four conditions were instructed that each target slide would be shown only once, that they should try to remember as many items as possible, and that the order of presentation was not important. Subjects in the control group received no further instructions before viewing the target slides. Subjects in the noise condition were informed that they would be listening to the sound of jet planes while the target slides were shown. The sound of jet planes was provided by a cassette tape of the Cook Vector-stereo record, 1270, side B, “Jet Dynamics,” played at 80-86 db (A scale), a level reported to be somewhat anxiety-producing (Kryter, 1970). In the threat condition, subjects were advised that each individual would be closely observed by the experimenter so that their behavioral signs of attention, such as posture and facial expression, could be noted and later correlated with their recognition memory scores. The experimenter then sat facing the subjects and gave the appearance of evaluating their behavior by ticking off “items” on an “evaluation sheet” while the target slides were shown. In all other conditions, the experimenter was seated behind the subjects during presentation of the target slides. In the reward condition, subjects were encouraged to do their best and were told that, as an incentive to do well, a reward having a value of about $10 would be awarded to the person receiving the highest recognition memory score. After receiving their instructions, all subjects viewed the target slides which were presented for a duration of 5 set each, with a I-set interval between slides. Subsequently, all subjects completed the STAI state anxiety questionnaire. Subjects then viewed both the target and distractor slides which were shown in random sequence for a duration of 8 set each, with an interstimulus interval of 1 sec. They had been instructed to indicate in a response booklet whether or not each slide had been previously shown and to indicate the degree of confidence in their decision by checking the item on a dpoint response scale ranging from “certain yes” to “certain no.” The receiver operating characteristic (ROC) curve parameter, d’, was computed for both pictures and words with EPCROC, a program developed by Ogilvie and Creelman (1%8) which provides a maximum-likelihood estimation of ROC parameters for the rating method.
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RESULTS In the analysis of the data, the .05 level of confidence was applied to all statistical tests, and individual comparisons between means were assessed by the Newman-Keuls procedure. In the preliminary analyses, the effects of stress conditions (control, noise, threat, and reward) on state anxiety and recognition memory were independently examined by means of one-way analyses of variance. There were no significant differences in state anxiety between the four stress conditions (F < 1). With respect to the recognition memory performance, significant differences between stress conditions were observed for words, F(3, 116) = 5.90, MS, = 1.20, but not for pictures, F(3, 116) = 1.90, MS, = 1.66. Recognition memory for words in both the reward and noise conditions was greater than in the threat condition, and memory for words’in the reward condition was also greater than in the control condition. No other differences were observed. The interactive effects of personality variables, (high and low groups), and stress conditions on recognition memory were examined by means of two-way analyses of variance for independent groups. High and low groups on each scale were formed by dichotomizing at the median scores for each scale. In these analyses, the effects of stress conditions on recognition memory for words previously described were maintained and are not restated in the subsequent analyses. However, the differential contribution of high and low personality groups to the main effect are noted. The hit rates and false alarm rates have also been considered relevant to the discussion of individual differences in memory performance (Mueller, 1976, 1979). Therefore, these measures were subject to the same statistical analyses used for d’ . Trait Anxiety
No significant main effect of trait anxiety was observed. However, a significant interaction of trait anxiety with stress was evident in the word condition, F(3, 112) = 3.17, MS, = 1.13. Subjects high in trait anxiety obtained greater recognition memory scores for words under the reward condition than those high in trait anxiety under the threat, control, and noise conditions. The recognition memory for pictures and words of high and low trait anxiety groups are shown in Fig. 1. State Anxiety
A main effect of state anxiety was observed with recognition memory for pictures, F(1, 112) = 5.06, MS, = 1.61. Individual comparisons between means revealed that the contribution of state anxiety occurred primarily in the threat condition, with subjects low in state anxiety obtaining
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LOW TRAiT ANXIETY
Ery
1
HIGH TRAIT ANXIETY
zrr
“,
6.0
^
i
3.0
I
2.0 /
STRESS
FIG. 1. Recognition anxiety.
CONDITIONS
memory for pictures and words of groups high and low in trait
higher recognition scores for pictures under the threat condition than those high in state anxiety. The recognition memory performance for pictures and words of high and low state anxiety groups are shown in Fig. 2. Neuroticism
The personality dimension of N also contributed differentially to the main effects of stress on recognition memory for words. The performance of subjects high in N was enhanced under the reward condition. High 6.0
I
LOW STATE ANXIETY
;z;”
1
HIGH STATE ANXIETY
;rr”ds”
1
‘.O.---CONTROL STRESS
FIG. 2. Recognition anxiety.
REWARD CONDITIONS
memory for pictures and words of groups high and low in state
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RECOGNITION
N subjects performed better in the reward condition than high N groups in each of the other conditions. The recognition memory results for high and low N groups for both pictures and words are shown in Fig. 3. Extraversion In the recognition memory for words, the performance of extraverts remained constant across conditions. The performance of introverts was significantly lower under the threat condition than that of the introvert groups under both the noise and reward conditions. This result was also noted in the recognition memory for pictures, where a stress x E interaction was observed, F(2, 112) = 3, MS, = 1.59. Introverts under the threat condition again scored significantly lower than introverts under both the noise and reward conditions. The recognition memory performance for pictures and words of introverts and extraverts is shown in Fig. 4. Psychoticism A significant main effect for P was observed in the recognition memory for pictures, F(1, 112) = 7.54, MS, = 1.33, and a stress x P interaction was also observed, F(3, 112) = 8.63, MS, = 1.33. For words, differences between stress conditions were evident, F(3, 112) = 5.44, MS, = 1.14, and a stress x P interaction was also noted, F(3, 112) = 2.53, MS, = 1.14, p < .06. Individual comparisons between means indicated that the high P group in the reward condition obtained greater recognition memory scores than the high P groups in the threat, noise, and control conditions for both pictures and words. The low P groups in the noise condition obtained greater d’ scores than the low P groups in the control condition LOW NEUROTICISM 6.0
I
HIGH NEUROTICISM
STRESS
FIG.
3.
Recognition
memory
for pictures
Words Pictures
. a
Words
.
CONDITIONS
and words
of groups
high and low iu neuroticism. .
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STELMACK ET AL. INTROVERSION
6.0.
EXTRAVERSION
f D
%
1:
Pictures Words
a -
q
k
‘.OcoNfnoL STRESS
CONDITIONS
4. Recognition memory for pictures and words of groups high (extraverts) and low (introverts) in extraversion. FIG.
for both pictures and words, The low P group in the noise condition also obtained greater scores for words than the low P group in the reward condition and for pictures than the low P group in the threat condition. Low P groups performed better than high P groups in the noise condition for both pictures and words and in the threat condition for pictures. Recognition memory performance for pictures and words for groups high and low in P are shown in Fig. 5.
I
LOW PSYCHOTICISM
Pictures 0 Words .
HIGH PSYCHOTICISM
E,;;
6.0 1
STRESS
5. Recognition psychoticism. . FIG.
“.
CONDITIONS
memory for pictures and words of groups high and low in
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Effects of Stress on Hits and False Alarms
Hits and false alarm rates were also subjected to independent analysis following the same procedures as for d’. The analysis of hit rates was essentially parallel to that described for d’. In the analysis of false alarm rates, only an interaction between stress and trait anxiety for false alarms for pictures was observed, F(3, 112) = 3.31, MS, = 27.77. This interaction was due mainly to the fact that subjects low in trait anxiety made more false alarms under the control condition than low trait anxiety subjects under the noise condition. Conversely, subjects high in trait anxiety scored more false alarms under the noise condition than did high trait anxiety subjects under the control condition. Correlation of d’ and Personality
In addition to the analysis of variance, which allows the comparison of the performance of the personality groups across the stress conditions, correlational analysis, which is sensitive to individual variation along the personality dimensions, was applied to these data. Table 2 illustrates the strength of the relationships between the personality dimensions and recognition performance within each of the stress conditions. In the control condition, recognition memory was not correlated with any personality variable. Recognition memory for both pictures and words was negatively correlated with P in the noise condition. In the threat condition, recognition memory for both pictures and words was positively TABLE CORRELATIONS
OF RECOGNITION
2
MEMORY (d’) WITH PERSONALITY STRESS CONDITIONS
DIMENSIONS
UNDER FOUR
Personality dimension STAI Stress condition
Stimulus type
Control (iv = 30)
Pictures Words
Noise (N = 30)
Pictures Words
d
Threat (Iv = 30)
Pictures Words
d’
Reward (N = 30)
Pictures Words
d’
* p < .05. ** p < .Ol.
d’
EPQ
Trait-state
anxiety
N
.oo
d’
-.06
- .09 .20
.Ol .04
d’
- .Ol -.16
-.22 - .23
- .05 -.05
- .34* - .41**
- so** - .48**
-.13 - .31*
.03 .34*
- .40** .04
.07 .2S
d’
d’
E
P
-.14 -.Ol
.05 -.11
- .05 .I1
- .55** - .40**
.32* .43** .I3 .04
- .46** -.I2 .30* .09
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correlated with E. Recognition memory for words in the threat condition was negatively correlated with trait anxiety, state anxiety, and N, while memory for pictures was negatively correlated with trait anxiety, state anxiety and P. In the reward condition, memory for pictures was positively related to P, and negatively related to state anxiety. Memory for words was positively correlated with trait anxiety in the reward condition. DlSCUSSlON
The performance decrement anticipated for high-anxiety subjects, who are thought to be sensitive to evaluation and ego threat, was not observed in the threat condition. Although the memory performance for words of high-anxiety subjects showed a slight decrement from the control group, the performance increment for low-anxiety subjects and performance decrement for high-anxiety subjectsreported in learning studies(Nicholson, 1958; Sarason, 1956, 1957) was not found in this recognition memory paradigm. Some support for an inverse relationship between trait anxiety and recognition memory performance, however, was evident in the correlation analysis of the threat condition. That is, trait anxiety was negatively correlated with recognition memory for both pictures and words in the threat condition. Although this relationship was somewhat more pronounced in recognition memory for words than for pictures, these effects were essentially parallel. Thus, the association of anxiety and memory performance was not determined by differences in the encoding of the physical and semantic features of the stimulus items. It is interesting to note, however, that for recognition memory for words subjects high in trait anxiety were sensitive to the reward condition where they displayed a performance increment relative to all other conditions. This result cannot be easily accounted for in terms of explanations of anxiety currently advocated. On the contrary, it could be argued that the reward condition, which is inherently competitive, implies some degree of personal evaluation and ego threat which should have consequences in the opposite direction of those observed. In view of the high correlation between trait anxiety and neuroticism, it is not surprising that the performance of high and low neuroticism groups was identical to that described for the trait anxiety groups. State anxiety, however, predicted differences in recognition memory for pictures in the threat condition. To some extent, this finding supports the effectiveness of the ego threat instructions. In this respect, state anxiety, which has been found to be sensitive to ego threat manipulations (Spielberger, 1972), is a better predictor than trait anxiety of differences in recognition memory performance, as has been previously suggested(M. W. Eysenck, 1979). For both pictures and words, the recognition memory performance for introverts in the threat condition was lower than in the noise and reward
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conditions. Subjects who are low in E, then, rather than those high in N or trait anxiety, are sensitive to ego threat. On the basis of differences in stimulus reception and encoding inferred from electrophysiological work, it was expected that the recognition memory performance, which emphasizes encoding processes, would be greater for introverts than for extraverts in the control condition. This view was prompted by the convergence of evidence which shows that enhanced electrodermal (Stelmack et al., 1983) and enhanced evoked potential responses (Warren, 1980) are related to enhanced memory performance and that introverts display enhanced electrodermal and evoked potential responses to stimulation (Stelmack & Plouffe, 1983). This expectation, however, was not confirmed. Since the subjects for the present study were not selected from extreme groups along a specific dimension, it could be argued that the encoding effects are not sufficiently strong to differentiate the high and low groups formed by a median split. Similarly, no differences between extraverts and introverts were observed in the noise condition where the noise was expected to increase the cortical arousal of introverts, fostering a performance decrement for this group. Overall, the performance of introverts would seem to conform most closely to expectations from Gray’s (1981) model where introversion is thought to depend on heightened sensitivity to aversive conditions. The analysis of the recognition memory performance across conditions with respect to the P dimension is quite striking, with negative correlations observed in the noise and threat condition, indicating that the high P scorers were rather impervious to these manipulations while the low P scorers appeared to be particularly sensitive to the noise condition where their performance was significantly greater than in the control condition. Evidence from electrophysiological studies seems to suggest that high P is associated with low levels of electrodermal arousal (Hare, 1975; Schalling, Linberg, Levander, & Dahlin, 1973; Stelmack, Plouffe, & Falkenberg, 1983). TO the extent to which noise induces an increase in arousal, one would expect that the memory performance of the high P groups would be facilitated in that condition, an expectation contrary to the present finding. Thus, the arousal hypothesis would not seem to apply to the P group. On the other hand, high P scorers displayed greater recognition memory performance in the reward condition relative to high P groups in the other conditions. This finding is consistent with current views regarding the sensitivity of high impulsive subjects to reward (Gray, 1981). The effect of reward on memory performance generally is not clear. It is known, however, that incentives increase heart rate, which is a widely employed index of arousal (cf. Fowles, 1983). In the present case, one may only suppose that the reward condition served to increase the arousal, or interest, of the high P subjects. In this regard, the effect is similar to that reported by Bowyer et al. (1983) who found that the
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recognition memory performance of high-impulsive subjects was facilitated with caffeine-induced arousal. There is a clear need for a program of investigative studies to explicate the specific conditions under which the memory performance of high P scorers is facilitated before inferences regarding the mechanisms that mediate the memory effects can be stated. It should also be noted that false alarm rates did not contribute substantially to the effects observed for the P groups. Indeed, the only notable finding was that the false alarm rate for subjects high in trait anxiety was greater under the noise condition than under the control condition. Otherwise the influence of the stress conditions on false alarm rates for the personality groups was unremarkable. The results of the present experiment indicate that research relating personality and memory would benefit from structuring conditions to exploit the determinants of the personality dimensions. It is interesting to note that individual differences in memory did not emerge under neutral conditions, but only when stress was applied. A salient effect was the performance decrement displayed by introverts under the threat condition. With regard to individual differences in trait anxiety and the effect of stress on memory, the extraversion dimension would seem to be more strongly implicated than neuroticism. The interactive effects on recognition memory of P with noise and reward underscore the inadequacies of the arousal hypothesis. All three stress conditions employed in this experiment can be seen to increase arousal, but the influence on performance is different, even contradictory, for specific personality dimensions. Clearly, the arousal hypothesis cannot be universally invoked to account for the personality effects and a more precise formulation of hypotheses is demanded. Indeed, there is considerable evidence to indicate that arousal is a multidimensional phenomenon (cf. Fowles, 1980). In this regard, recent developments in personality theory mentioned here may be helpful. Current electrophysiological measurement may also prove useful in differentiating “arousal” conditions, although the designs of such experiments are a considerable challenge. For the present, the mechanisms that mediate the memory effects for the personality dimensions investigated in this report are obscure. REFERENCES Bowyer, P. A., Humphreys, M. S., & Revelle, W. (1983). Arousal and recognition memory: The effects of impulsivity, caffeine and time on task. Personality and Individual Differences, 4, 41-49. Broadhurst, P. L. (1959). The interaction of task difficulty and motivation: The YerkesDodson Law revived. Acra Psychologia, 16, 321-338. Egan, J. P., Schulman, A. I., & Greenberg, G. Z. (1959). Operating characteristics determined by binary decisions and by ratings. Journal of the Acoustical Society of America, 31, 768-773. Eysenck, H. J. (1967). The biological basis of personality, Springfield, IL: Thomas.
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Spielberger, C. D., Gorsuch, R. L., 8c Lushene, R. E. (1970). Manual for the State-Trait Anxiety Inventory. Palo Alto, CA: Consulting Psychologists Press. Stelmack, R. M. (1981). The psychophysiology of extraversion and neuroticism. In H. J. Eysenck (Ed.), A model for personality. Heidelberg: Springer-Verlag. Stelmack, R. M., & Plouffe, L. (1983). Introversion-extraversion: The Bell-Magendie law revisited. Personality and Individual Differences, 4, 371-442. Stelmack, R. M., Plouffe, L. M., & Falkenberg, W. (1983). Extraversion, sensation-seeking and electrodennal response: Probing a paradox. Personality and Individual Differences, 4, 607-614. Stelmack, R. M., Plouffe, L. M., & Winogron, H. W. (1983). Recognition memory and the orienting response: An analysis of the encoding of pictures and words. Biological Psychology, 16, 49-63. Warren, L. R. (1980). Evoked potential correlates of recognition memory. Biological Psychology, 11, 21-35.
OF RESEARCH
IN PBRSONALITY
18,
164-178
(1984)
Personality and the Effects of Stress on Recognition Memory ROBERT M. STELMACK, LINDA D. WIELAND,MARY U. WALL, ANDLOUISEPLOUFFE University
of Ottawa
The experiment examined the contribution of anxiety, extraversion, neuroticism, and psychoticism to recognition memory for pictures and words using a signal detection method. Independent groups of subjects performed a recognition memory task under one of four conditions (control, noise, threat, and reward) that was intended to capitalize on dispositions which characterize the personality dimensions. In an ego threat condition involving personal evaluation, introverts displayed a performance decrement relative to noise and reward conditions. Psychoticism was inversely related to performance in the noise and threat conditions and directly related in a reward condition. In general, J. A. Gray’s (1981) model of anxiety and impulsiveness accommodates much of the data, but the mechanisms which mediate the influence of personality on memory performance are not clear.
Eysenck’s typology of personality has recently been subject to important revisions (Eysenck & Eysenck, 1975). Moreover, evidence from psychophysiological and physiological research has prompted new speculations on the biological basis of Eysenck’s personality dimensions. The present study was designed to examine the contribution of personality differences to recognition memory performance in the context of these developments. Eysenck (1967) proposed that individual differences between introverts and extraverts in a wide range of social and psychiatric behaviors may depend on differences in cortical arousal, with introverts characterized by lower thresholds of arousal than extraverts. From this general hypothesis, individual differences between introverts and extraverts have been predicted in a number of experimental paradigms that considered such processes as sensory sensitivity, attention, conditioning, and memory (cf. Eysenck, 1981). During this period, the validity of the arousal hypothesis has been investigated intensively with physiological and psychophysioThis research was supported by the Social Sciences and Humanities Research Council of Canada, Grant 410-77-0833 and by the Natural Science and Engineering Research Council of Canada, Grant A7057. Address requests for reprints to Robert M. Stelmack, School of Psychology, University of Ottawa, Ottawa, Ontario KlN6N5, Canada. 164 0092-6566184 Copyright All rights
$3.00
Q 1984 by Academic Press, Inc. of reproduction in any form reserved.
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logical methods. Consequently, a number of amendments to the basic hypothesis have been proposed. Foremost among these is the schema advocated by Gray (1981), who proposed that anxiety (neurotic introversion) is dependent on mechanisms mediating a behavioral inhibition system which is reflected in differences in sensitivity to punishment or threats of punishment, and that individual differences in impulsiveness depend on an appetitive motivational system which is reflected in differences in susceptibility to reward. At the same time, there have been significant revisions to Eysenck’s typology (Eysenck & Eysenck, 1964) with the development of the Eysenck Personality Questionnaire (EPQ) and the introduction of a psychoticism or tough-mindedness scale (Eysenck & Eysenck, 1975). In this revision, impulsivity items from the extraversion (E) scale have been removed and the psychoticism (P) scale has been shown to correlate positively with impulsiveness measures (Eysenck & Eysenck, 1978). With the emergence of impulsiveness as a central personality construct, it is not clear whether individual variation in memory effects previously attributed to E will be maintained or whether this variation will be attibuted to P. Work in our own laboratory has primarily addressed the arousal hypothesis by examining differences between introverts and extraverts in their response to sensory stimulation (Stelmack, 1981). Evidence from several sources, including psychophysical, electrodermal, and evoked potential measures, indicate that introverts display an enhanced response to sensory stimulation. We have argued elsewhere that these effects may be referred to differences at the level of the sensory nerve (Stelmack & Plouffe, 1983). These findings demonstrate clear differences between introverts and extraverts in stimulus reception and encoding processes; one would expect such differences to be expressed in memory performance. It is from the context of these recent developments that the present study examined the relationship of personality differences to recognition memory performance. Although recent advances in personality theory have not been extensively exploited in the investigation of individual differences in memory, there has been good progress in articulating differences in the operation of memory processes of subjects who differ in degree of anxiety, or E and neuroti+sm (N). The work most extensively reported has extended from the Yerkes-Dodson law where the relationship between anxiety and task difficulty has been explored (cf. Broadhurst, 1959). To a large extent, that research was based on the view that task difficulty, or other stressors such as noise or ego threat, increases arousal and that arousal has interactive effects with memory performance. As expected, high-anxiety subjects have been found to display performance superior to that of low-anxiety subjects on simple paired associate learning tasks, while low-anxiety
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subjects are superior on more difficult tasks (cf. M. W. Eysenck, 1977). These effects, however, have not been consistently observed and the processes that mediate the effects are not well understood (Mueller, 1979). Stress induced by negative feedback or evaluation has also been found to both increase levels of self-reported anxiety in introverts (Freemont, Means, & Means, 1970) and adversely affect memory performance in high-anxiety subjects (Sarason, 1956). In a more recent study, no differences between high- and low-anxiety subjects were observed in a retrieval task where ego threat instructions were applied (Mueller & Wherry, 1982). Overall, however, there has been surprisingly little work investigating the effects of stress on memory for subjects who differ in degree of anxiety, especially in view of the prominence given to susceptibility to stress in current theories of anxiety (Spielberger, 1972). Moreover, it is not clear whether it is the E or N factors, or both, which contribute to the effects of anxiety on memory performance. Recent research suggests that the effects of anxiety on memory are reflected in individual differences in the encoding of semantic and physical characteristics of verbal stimuli. The findings lend themselves to a “levels of processing” interpretation whereby the more elaborate organization or effort which is required for the encoding of semantic features is restricted with high-anxiety subjects. Schwartz (1975, 1979) found that the semantic properties of verbal material, rather than the physical properties, were more readily accessed by introverts than extraverts. Mueller (1979) also reported that high-anxiety subjects encoded fewer semantic features, encoded less elaborately, and were less flexible in their use of alternative memory strategies. Overall, this research indicates that qualitative differences in encoding may be an important focus for explicating the effects of anxiety on memory performance. Recognition memory, with its emphasis on encoding rather than retrieval processes (cf. Mandler, 1980) may be a useful paradigm for examining the encoding effects displayed by anxious subjects in previous research. In the present inquiry, recognition memory for pictures and words of subjects who differ in degree of anxiety, E, N, and P was examined under four stress conditions: noise, threat, reward, and control (no treatment). Employing both verbal and pictorial stimuli exploits the distinction between semantic and physical characteristics that have been implicated in the demonstration of differences in the memory performance of highand low-anxiety subjects. The conditions applied in this study were intended to capitalize on dispositions which are currently thought to characterize the personality dimensions E, N, and P measured by the EPQ. Thus, a noise condition was expected to promote a general increase in arousal which would be reflected in differences in recognition memory performance along the E
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dimension. In this condition, introverts and extraverts, if they are characterized by differences in cortical arousal (Eysenck, 1967) would be differentially influenced, with introverts showing a decrement and extraverts showing an increment relative to their performance in the control condition. With respect to the threat condition, a number of authors maintain that high-anxiety subjects are particularly sensitive to situations of perceived threat to self-esteem (Spielberger, 1972), and Gray (1981) has argued that sensitivity to aversive stimuli is a fundamental determinant of anxiety. If anxiety has deleterious effects on encoding processes as has been suggested, the threat condition should exacerbate those effects. The reward condition was introduced to focus on impulsiveness, a characteristic of the P dimension. Since impulsive subjects are thought to be more susceptible to reward than low impulsives (Gray, 1981), it may be expected that their performance would be influenced, although the dynamics of this process are not clear. One may suppose that impulsive subjects would be inclined to make more false positives in a reward condition which may result in a performance decrement. On the other hand, there is some evidence which indicates that recognition memory performance of high-impulsive subjects is facilitated with increases in arousal (Bowyer. Humphreys, & Revelle, 1983). If the reward condition simply serves to increase arousal or interest, the performance of high-impulsive subjects may be facilitated. In the present study, anxiety has been defined by the State-Trait Anxiety Inventory (STAI) (Spielberger, Gorsuch, & Lushene, 1970). Because the state anxiety measure is situation specific, it has been suggested that it may be more sensitive to the effects of stress on memory performance than trait anxiety which is regarded as an endogenous disposition (M. W. Eysenck, 1979). In addition to P, the EPQ provides independent measures of E and N, both of which correlate with trait anxiety; this allows the contribution of E and N in the effects of anxiety on recognition memory performance to be assessed. METHOD
Subjects Subjects were 120 university and community college students, 80 women and 40 men. The mean age was 23.5 years, SD = 5.41. Subjects performed a recognition memory task under one of four conditions to which they had been randomly assigned: control, noise, threat, or reward. Each condition contained 20 women and 10 men. All subjects were administered the STAI and the EPQ. The means and standard deviations for the personality variables were as follows: trait anxiety, X = 39.01 (SD = 9.62); extraversion, X = 14.05 (SD = 4.77); neuroticism, X = 11.07 (SD = 5.35); and psychoticism, X = 3.11 (SD = 2.42). The four groups did not differ on these personality dimensions (F < 1). Pearson correlations between STAI and EPQ scores for these subjects are shown in Table 1. There was no remarkable departure from this pattern of intercorrelations within each of the four groups.
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CORRELATIONOF PERXINALITY DIMENSIONS(N = 120) STAI
EPQ E -
E N P
N
P
Trait anxiety
-0.13 -
-0.19* 0.16* -
- 0.24** 0.76** 0.26**
* p < .05. ** p < .Ol. Apparatus and Procedure The stimuli were 140 slides of concrete words in pica type and 140 slides of unambiguous line drawings of simple objects (Stehnack, PlouBe, & Winogron, 1983) which were presented by a Kodak carousel projector (Model 800). Half of the items in each category were randomly selected, mixed, and displayed as target stimuli during the acquisition phase of the recognition memory task, and the remainder were employed as distracters during the test phase. The general procedure followed the fixed-interval observation rating experiment described by Egan, Schulman, and Greenberg (1959). Subjects were tested individually or in small groups. After completing the EPQ and the STAI trait anxiety questionnaires, subjects in all four conditions were instructed that each target slide would be shown only once, that they should try to remember as many items as possible, and that the order of presentation was not important. Subjects in the control group received no further instructions before viewing the target slides. Subjects in the noise condition were informed that they would be listening to the sound of jet planes while the target slides were shown. The sound of jet planes was provided by a cassette tape of the Cook Vector-stereo record, 1270, side B, “Jet Dynamics,” played at 80-86 db (A scale), a level reported to be somewhat anxiety-producing (Kryter, 1970). In the threat condition, subjects were advised that each individual would be closely observed by the experimenter so that their behavioral signs of attention, such as posture and facial expression, could be noted and later correlated with their recognition memory scores. The experimenter then sat facing the subjects and gave the appearance of evaluating their behavior by ticking off “items” on an “evaluation sheet” while the target slides were shown. In all other conditions, the experimenter was seated behind the subjects during presentation of the target slides. In the reward condition, subjects were encouraged to do their best and were told that, as an incentive to do well, a reward having a value of about $10 would be awarded to the person receiving the highest recognition memory score. After receiving their instructions, all subjects viewed the target slides which were presented for a duration of 5 set each, with a I-set interval between slides. Subsequently, all subjects completed the STAI state anxiety questionnaire. Subjects then viewed both the target and distractor slides which were shown in random sequence for a duration of 8 set each, with an interstimulus interval of 1 sec. They had been instructed to indicate in a response booklet whether or not each slide had been previously shown and to indicate the degree of confidence in their decision by checking the item on a dpoint response scale ranging from “certain yes” to “certain no.” The receiver operating characteristic (ROC) curve parameter, d’, was computed for both pictures and words with EPCROC, a program developed by Ogilvie and Creelman (1%8) which provides a maximum-likelihood estimation of ROC parameters for the rating method.
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RESULTS In the analysis of the data, the .05 level of confidence was applied to all statistical tests, and individual comparisons between means were assessed by the Newman-Keuls procedure. In the preliminary analyses, the effects of stress conditions (control, noise, threat, and reward) on state anxiety and recognition memory were independently examined by means of one-way analyses of variance. There were no significant differences in state anxiety between the four stress conditions (F < 1). With respect to the recognition memory performance, significant differences between stress conditions were observed for words, F(3, 116) = 5.90, MS, = 1.20, but not for pictures, F(3, 116) = 1.90, MS, = 1.66. Recognition memory for words in both the reward and noise conditions was greater than in the threat condition, and memory for words’in the reward condition was also greater than in the control condition. No other differences were observed. The interactive effects of personality variables, (high and low groups), and stress conditions on recognition memory were examined by means of two-way analyses of variance for independent groups. High and low groups on each scale were formed by dichotomizing at the median scores for each scale. In these analyses, the effects of stress conditions on recognition memory for words previously described were maintained and are not restated in the subsequent analyses. However, the differential contribution of high and low personality groups to the main effect are noted. The hit rates and false alarm rates have also been considered relevant to the discussion of individual differences in memory performance (Mueller, 1976, 1979). Therefore, these measures were subject to the same statistical analyses used for d’ . Trait Anxiety
No significant main effect of trait anxiety was observed. However, a significant interaction of trait anxiety with stress was evident in the word condition, F(3, 112) = 3.17, MS, = 1.13. Subjects high in trait anxiety obtained greater recognition memory scores for words under the reward condition than those high in trait anxiety under the threat, control, and noise conditions. The recognition memory for pictures and words of high and low trait anxiety groups are shown in Fig. 1. State Anxiety
A main effect of state anxiety was observed with recognition memory for pictures, F(1, 112) = 5.06, MS, = 1.61. Individual comparisons between means revealed that the contribution of state anxiety occurred primarily in the threat condition, with subjects low in state anxiety obtaining
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LOW TRAiT ANXIETY
Ery
1
HIGH TRAIT ANXIETY
zrr
“,
6.0
^
i
3.0
I
2.0 /
STRESS
FIG. 1. Recognition anxiety.
CONDITIONS
memory for pictures and words of groups high and low in trait
higher recognition scores for pictures under the threat condition than those high in state anxiety. The recognition memory performance for pictures and words of high and low state anxiety groups are shown in Fig. 2. Neuroticism
The personality dimension of N also contributed differentially to the main effects of stress on recognition memory for words. The performance of subjects high in N was enhanced under the reward condition. High 6.0
I
LOW STATE ANXIETY
;z;”
1
HIGH STATE ANXIETY
;rr”ds”
1
‘.O.---CONTROL STRESS
FIG. 2. Recognition anxiety.
REWARD CONDITIONS
memory for pictures and words of groups high and low in state
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RECOGNITION
N subjects performed better in the reward condition than high N groups in each of the other conditions. The recognition memory results for high and low N groups for both pictures and words are shown in Fig. 3. Extraversion In the recognition memory for words, the performance of extraverts remained constant across conditions. The performance of introverts was significantly lower under the threat condition than that of the introvert groups under both the noise and reward conditions. This result was also noted in the recognition memory for pictures, where a stress x E interaction was observed, F(2, 112) = 3, MS, = 1.59. Introverts under the threat condition again scored significantly lower than introverts under both the noise and reward conditions. The recognition memory performance for pictures and words of introverts and extraverts is shown in Fig. 4. Psychoticism A significant main effect for P was observed in the recognition memory for pictures, F(1, 112) = 7.54, MS, = 1.33, and a stress x P interaction was also observed, F(3, 112) = 8.63, MS, = 1.33. For words, differences between stress conditions were evident, F(3, 112) = 5.44, MS, = 1.14, and a stress x P interaction was also noted, F(3, 112) = 2.53, MS, = 1.14, p < .06. Individual comparisons between means indicated that the high P group in the reward condition obtained greater recognition memory scores than the high P groups in the threat, noise, and control conditions for both pictures and words. The low P groups in the noise condition obtained greater d’ scores than the low P groups in the control condition LOW NEUROTICISM 6.0
I
HIGH NEUROTICISM
STRESS
FIG.
3.
Recognition
memory
for pictures
Words Pictures
. a
Words
.
CONDITIONS
and words
of groups
high and low iu neuroticism. .
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6.0.
EXTRAVERSION
f D
%
1:
Pictures Words
a -
q
k
‘.OcoNfnoL STRESS
CONDITIONS
4. Recognition memory for pictures and words of groups high (extraverts) and low (introverts) in extraversion. FIG.
for both pictures and words, The low P group in the noise condition also obtained greater scores for words than the low P group in the reward condition and for pictures than the low P group in the threat condition. Low P groups performed better than high P groups in the noise condition for both pictures and words and in the threat condition for pictures. Recognition memory performance for pictures and words for groups high and low in P are shown in Fig. 5.
I
LOW PSYCHOTICISM
Pictures 0 Words .
HIGH PSYCHOTICISM
E,;;
6.0 1
STRESS
5. Recognition psychoticism. . FIG.
“.
CONDITIONS
memory for pictures and words of groups high and low in
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Effects of Stress on Hits and False Alarms
Hits and false alarm rates were also subjected to independent analysis following the same procedures as for d’. The analysis of hit rates was essentially parallel to that described for d’. In the analysis of false alarm rates, only an interaction between stress and trait anxiety for false alarms for pictures was observed, F(3, 112) = 3.31, MS, = 27.77. This interaction was due mainly to the fact that subjects low in trait anxiety made more false alarms under the control condition than low trait anxiety subjects under the noise condition. Conversely, subjects high in trait anxiety scored more false alarms under the noise condition than did high trait anxiety subjects under the control condition. Correlation of d’ and Personality
In addition to the analysis of variance, which allows the comparison of the performance of the personality groups across the stress conditions, correlational analysis, which is sensitive to individual variation along the personality dimensions, was applied to these data. Table 2 illustrates the strength of the relationships between the personality dimensions and recognition performance within each of the stress conditions. In the control condition, recognition memory was not correlated with any personality variable. Recognition memory for both pictures and words was negatively correlated with P in the noise condition. In the threat condition, recognition memory for both pictures and words was positively TABLE CORRELATIONS
OF RECOGNITION
2
MEMORY (d’) WITH PERSONALITY STRESS CONDITIONS
DIMENSIONS
UNDER FOUR
Personality dimension STAI Stress condition
Stimulus type
Control (iv = 30)
Pictures Words
Noise (N = 30)
Pictures Words
d
Threat (Iv = 30)
Pictures Words
d’
Reward (N = 30)
Pictures Words
d’
* p < .05. ** p < .Ol.
d’
EPQ
Trait-state
anxiety
N
.oo
d’
-.06
- .09 .20
.Ol .04
d’
- .Ol -.16
-.22 - .23
- .05 -.05
- .34* - .41**
- so** - .48**
-.13 - .31*
.03 .34*
- .40** .04
.07 .2S
d’
d’
E
P
-.14 -.Ol
.05 -.11
- .05 .I1
- .55** - .40**
.32* .43** .I3 .04
- .46** -.I2 .30* .09
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correlated with E. Recognition memory for words in the threat condition was negatively correlated with trait anxiety, state anxiety, and N, while memory for pictures was negatively correlated with trait anxiety, state anxiety and P. In the reward condition, memory for pictures was positively related to P, and negatively related to state anxiety. Memory for words was positively correlated with trait anxiety in the reward condition. DlSCUSSlON
The performance decrement anticipated for high-anxiety subjects, who are thought to be sensitive to evaluation and ego threat, was not observed in the threat condition. Although the memory performance for words of high-anxiety subjects showed a slight decrement from the control group, the performance increment for low-anxiety subjects and performance decrement for high-anxiety subjectsreported in learning studies(Nicholson, 1958; Sarason, 1956, 1957) was not found in this recognition memory paradigm. Some support for an inverse relationship between trait anxiety and recognition memory performance, however, was evident in the correlation analysis of the threat condition. That is, trait anxiety was negatively correlated with recognition memory for both pictures and words in the threat condition. Although this relationship was somewhat more pronounced in recognition memory for words than for pictures, these effects were essentially parallel. Thus, the association of anxiety and memory performance was not determined by differences in the encoding of the physical and semantic features of the stimulus items. It is interesting to note, however, that for recognition memory for words subjects high in trait anxiety were sensitive to the reward condition where they displayed a performance increment relative to all other conditions. This result cannot be easily accounted for in terms of explanations of anxiety currently advocated. On the contrary, it could be argued that the reward condition, which is inherently competitive, implies some degree of personal evaluation and ego threat which should have consequences in the opposite direction of those observed. In view of the high correlation between trait anxiety and neuroticism, it is not surprising that the performance of high and low neuroticism groups was identical to that described for the trait anxiety groups. State anxiety, however, predicted differences in recognition memory for pictures in the threat condition. To some extent, this finding supports the effectiveness of the ego threat instructions. In this respect, state anxiety, which has been found to be sensitive to ego threat manipulations (Spielberger, 1972), is a better predictor than trait anxiety of differences in recognition memory performance, as has been previously suggested(M. W. Eysenck, 1979). For both pictures and words, the recognition memory performance for introverts in the threat condition was lower than in the noise and reward
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conditions. Subjects who are low in E, then, rather than those high in N or trait anxiety, are sensitive to ego threat. On the basis of differences in stimulus reception and encoding inferred from electrophysiological work, it was expected that the recognition memory performance, which emphasizes encoding processes, would be greater for introverts than for extraverts in the control condition. This view was prompted by the convergence of evidence which shows that enhanced electrodermal (Stelmack et al., 1983) and enhanced evoked potential responses (Warren, 1980) are related to enhanced memory performance and that introverts display enhanced electrodermal and evoked potential responses to stimulation (Stelmack & Plouffe, 1983). This expectation, however, was not confirmed. Since the subjects for the present study were not selected from extreme groups along a specific dimension, it could be argued that the encoding effects are not sufficiently strong to differentiate the high and low groups formed by a median split. Similarly, no differences between extraverts and introverts were observed in the noise condition where the noise was expected to increase the cortical arousal of introverts, fostering a performance decrement for this group. Overall, the performance of introverts would seem to conform most closely to expectations from Gray’s (1981) model where introversion is thought to depend on heightened sensitivity to aversive conditions. The analysis of the recognition memory performance across conditions with respect to the P dimension is quite striking, with negative correlations observed in the noise and threat condition, indicating that the high P scorers were rather impervious to these manipulations while the low P scorers appeared to be particularly sensitive to the noise condition where their performance was significantly greater than in the control condition. Evidence from electrophysiological studies seems to suggest that high P is associated with low levels of electrodermal arousal (Hare, 1975; Schalling, Linberg, Levander, & Dahlin, 1973; Stelmack, Plouffe, & Falkenberg, 1983). TO the extent to which noise induces an increase in arousal, one would expect that the memory performance of the high P groups would be facilitated in that condition, an expectation contrary to the present finding. Thus, the arousal hypothesis would not seem to apply to the P group. On the other hand, high P scorers displayed greater recognition memory performance in the reward condition relative to high P groups in the other conditions. This finding is consistent with current views regarding the sensitivity of high impulsive subjects to reward (Gray, 1981). The effect of reward on memory performance generally is not clear. It is known, however, that incentives increase heart rate, which is a widely employed index of arousal (cf. Fowles, 1983). In the present case, one may only suppose that the reward condition served to increase the arousal, or interest, of the high P subjects. In this regard, the effect is similar to that reported by Bowyer et al. (1983) who found that the
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recognition memory performance of high-impulsive subjects was facilitated with caffeine-induced arousal. There is a clear need for a program of investigative studies to explicate the specific conditions under which the memory performance of high P scorers is facilitated before inferences regarding the mechanisms that mediate the memory effects can be stated. It should also be noted that false alarm rates did not contribute substantially to the effects observed for the P groups. Indeed, the only notable finding was that the false alarm rate for subjects high in trait anxiety was greater under the noise condition than under the control condition. Otherwise the influence of the stress conditions on false alarm rates for the personality groups was unremarkable. The results of the present experiment indicate that research relating personality and memory would benefit from structuring conditions to exploit the determinants of the personality dimensions. It is interesting to note that individual differences in memory did not emerge under neutral conditions, but only when stress was applied. A salient effect was the performance decrement displayed by introverts under the threat condition. With regard to individual differences in trait anxiety and the effect of stress on memory, the extraversion dimension would seem to be more strongly implicated than neuroticism. The interactive effects on recognition memory of P with noise and reward underscore the inadequacies of the arousal hypothesis. All three stress conditions employed in this experiment can be seen to increase arousal, but the influence on performance is different, even contradictory, for specific personality dimensions. Clearly, the arousal hypothesis cannot be universally invoked to account for the personality effects and a more precise formulation of hypotheses is demanded. Indeed, there is considerable evidence to indicate that arousal is a multidimensional phenomenon (cf. Fowles, 1980). In this regard, recent developments in personality theory mentioned here may be helpful. Current electrophysiological measurement may also prove useful in differentiating “arousal” conditions, although the designs of such experiments are a considerable challenge. For the present, the mechanisms that mediate the memory effects for the personality dimensions investigated in this report are obscure. REFERENCES Bowyer, P. A., Humphreys, M. S., & Revelle, W. (1983). Arousal and recognition memory: The effects of impulsivity, caffeine and time on task. Personality and Individual Differences, 4, 41-49. Broadhurst, P. L. (1959). The interaction of task difficulty and motivation: The YerkesDodson Law revived. Acra Psychologia, 16, 321-338. Egan, J. P., Schulman, A. I., & Greenberg, G. Z. (1959). Operating characteristics determined by binary decisions and by ratings. Journal of the Acoustical Society of America, 31, 768-773. Eysenck, H. J. (1967). The biological basis of personality, Springfield, IL: Thomas.
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Eysenck, H. J. (Ed.). (1981). A model for personality. Heidelberg: Springer-Verlag. Eysenck, H. J., & Eysenck, S. B. G. (1964). Manualfor the Eysenck Personality Inventory. San Diego: Educational and Industrial Testing Service. Eysenck, H. J., & Eysenck, S. B. G. (1975). Manual of the Eysenck Personality Questionnaire. San Diego: Educational and Industrial Testing Service. Eysenck, H. J., & Eysenck, S. B. G. (1978). Psychoticism as a dimension of personality. London: Hodder & Stoughton. Eysenck, M. W. (1977). Human memory: Theory, research, and individual differences. Oxford: Pergamon. Eysenck, M. W. (1979). Anxiety, learning and memory: A reconceptualization. Journal of Research
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