Advanced preparation of discrete finger responses: Nonmotoric evidence

Acta Psychologica North-Holland

117

72 (1989) 117-138

ADVANCED PREPARATION OF DISCRETE FINGER RESPONSES: NONMOTORIC EVIDENCE * James H. CAURAUGH University of Florida, Gainesville,

USA

James F. HORRELL Unwersity of Oklahoma, Accepted

December

Norman,

USA

1988

Motoric and nonmotoric accounts of advance preparation effects were investigated in two movement precuing experiments. The first experiment determined the effect of extended practice on advance preparation while the response fingers were aligned in adjacent and overlapped conditions. The second experiment compared performances across three hand positions: adjacent, overlapped, and crossed. Both experiments revealed Precue X Hand Position and Delay X Precue findings. These precuing results were interpreted as support for the nonmotoric translation processes explanation of advance preparation.

A current motor psychology debate centers on the explanations of enhanced reaction times (RTs) when advance information about two fingers on the same hand or about the two left- or right-most fingers is provided. Two explanations conflict in the emphasis of motoric and nonmotoric components. A motoric explanation proposed by Miller (1982, 1985) is based on a same hand advantage for short precue intervals. Miller has argued that enhanced performances for advance information about fingers on the same hand versus information about * This research was supported in part by a grant from the Research Council of the University of Oklahoma to James H. Cauraugh. Part of the second experiment was presented at the Annual Meeting of the North American Society for the Psychology of Sport and Physical Activity, June 1987, Vancouver, B.C., Canada. We extend our appreciation to T. Gilmour Reeve and H. Janey Barnes for their comments on an earlier version of this manuscript. We also thank James Winters for programming assistance on the main frame computer and Todd Ranks for programming the experiments. Requests for reprints should be sent to J.H. Cauraugh, Motor Behavior Laboratory, 25 FLG, University of Florida, Gainesville, FL 32611, USA.

OOOl-6918/89/$3.50

0 1989, Elsevier Science Publishers

B.V. (North-Holland)

118

J.H. Cuuraugh,J.F. Horrell / Ahmca prepumrron

fingers on different hands indicates that hand assignment is required before finger. On the other hand, Reeve and Proctor (1984, 1985a) have argued for a nonmotoric, stimulussresponse translation account to explain both same hand and different hands (left- or right-most fingers) results. Reeve and Proctor’s (1984, 1985a) argument is based on equivalent performances in prepared hand, finger, and neither conditions when the precue interval was lengthened from 1,000 ms to 3,000 ms. Furthermore, Reeve and Proctor (1984: experiment 3) introduced an overlapped hand position in which the response fingers were arranged in the following left to right horizontal order: right index, left middle, right middle, and left index. Results of the overlapped condition revealed that precued information about the two farthest left or right response fingers, a condition which represented different hands, enhanced RTs as well as information about two response fingers on the same hand. The primary evidence supporting the alternative interpretations of the nonmotoric effect espoused by Reeve and Proctor (1984, 1985a) and the motoric effect argued by Miller (1982) has been based on two 280 trial experiments and one 400 trial experiment. Granted, strong support for both explanations has been found with 280 and 400 trials, however, the obtained RTs may reflect a lack of consistent performance. That is, as subjects learn the cognitive orientation of the task, performances may be inconsistent (Anderson 1987). Or put differently, inconsistent RTs may be evident as subjects determine a response criterion for accuracy and latency (Pachella 1974). A differentiation of inconsistent and consistent RT responses seems important in light of the evidence of improved RT scores with practice 1968: 83). (Mowbray and Rhoades 1959; Seibel 1963; Welford Schneider (1985) and Welford (1986) have further discussed mean RT performance efficiency differences in highly practiced or trained subjects versus less practiced or trained subjects. Performance is more representative of the optimum in the highly practiced condition. A question that remains unanswered is whether the response preparation processes change across an extended number of trials. Therefore, one purpose of the present experiments was to determine the effect of practice on response preparation. More test trials were administered in each of the present experiments (1,600 and 560 trials, respectively) than in previous discrete finger response preparation

J. H. Cauraugh, J.F. Horrell / Advance preparation

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An important reason for the increased number of trials was the RT distribution changes reported by Rabbitt (1981). He showed that the primary effect of practice on speeded responses is to change the shape of their distribution. More precisely, the tail of long responses is reduced. A second purpose of experiment 2 was to investigate response preparation while the index and middle fingers of each hand were positioned in a new horizontal alignment in which the index fingers were crossed. Miller (1985) criticized the overlapped hand position condition devised by Reeve and Proctor (1984) because it produced an unnatural finger alignment. Briefly, in the overlapped finger alignment, the index fingers of each hand were positioned on the opposite side of the response keys (e.g. right index finger on the farthest left key). (A detailed explanation of the overlapped condition is provided in experiment 1.) According to Miller, this different response set produced a new, slower type of response preparation that enhanced RT performance when two fingers on different hands (i.e. a side advantage) were prepared versus the preparation of two fingers on the same hand. The new crossed index finger position produced a more neutral alignment than the overlapped position. Key press responses were readily executed with crossed index fingers (Cauraugh 1987). Comparisons of mean RTs for adjacent, overlapped, and crossed conditions were completed in experiment 2 (Rosenbaum 1980). A third purpose of the present experiments was to introduce a trial block analysis to cleanly differentiate mean RTs. Previous response preparation studies computed mean delay by precue RTs while collapsing across all the test trials. Such a procedure fails to differentiate ‘correct RT responses completed early in the experiment versus later responses. Extreme scores and outlier data are more likely in preliminary trials. A complete trial block analysis would reveal any response pattern changes across the full experiment. The inclusion of a trial blocks factor in the experimental design produced detailed statistical information. Reporting this detailed information is consistent with suggestions by Yates (1983) and Roberts (1983). studies.

Experiment 1 The first experiment was designed to further investigate response preparation processes over an extended period of time. A trial block analysis of the RT means

across extended practice (1.600 trials) should help identify any shifts in the response patterns for different mental operations. Such mental operations as nonmotoric decision making processes may exhibit different response patterns than motoric processes. More explicitly, Schmidt (1988) and Teichner and Krebs (1974) have stated that RT patterns attributed to nonmotoric processes and motoric processes are dissimilar patterns over time. Both types of processes predict efficient responses and decreased RTs with practice, however, the response patterns will be different. As a function of practice, the nonmotoric, translation explanation predicts that the various precued conditions will display equivalent performance (Reeve and Proctor 1985b; Welford 1968). In contrast, the motoric process predicts that the differences in the various precued conditions will be maintained (e.g. advanced precued hand will facilitate RT performance more than precued finger or neither ) over extended practice. Collapsing the RT data for each precue condition and precue delay interval across a large number of trials may mask subtle shifts in the pattern of responding. In experiment 1. two hand position groups (adjacent and overlapped) were administered 1,600 trials on two consecutive days of testing. Ten trial blocks were administered each day and mean correct RT performance was computed for each block. The experimental design was a five-factor design with hand position a between-subjects factor and day. trial block, delay, and precue within-subjects factors. The specific analysis was a 2 x 2 x 10 X 4 x 4 mixed design ANOVA. Adjacent and overlapped hand positions were tested because the interpretation of adjacent and overlapped results was central to the debate about motoric response preparation effects (Miller 1982, 1983. 1985) and nonmotoric translation processes (Reeve and Proctor 1984. 1985a). New response preparation information based on an extended amount of practice (i.e. in comparison to previous response preparation studies) may help resolve the motoric and nonmotoric issue. Method Subjects Sixteen undergraduate student volunteers participated in two consecutive days of testing and received one motor learning experimentation credit. Five females and three males were randomly assigned to each of the two hand positions. Apparatus An IBM XT microcomputer was programmed to control the experiment. The keyboard and color/graphics monitor were standard IBM equipment. Four plus sign characters ( + ) presented horizontally in the center of the screen served as a warning signal. The total width (20 mm) of the four plus signs was eight character positions. The warning signal was presented in the first. third, sixth. and eighth positions (Miller 1982). Two separate rows beneath the warning signal were used for the precue signal (two or four plus signs) and the reaction (target) stimulus. The reaction stimulus was a single plus sign which always occurred directly below one of the two precued position plus signs. For the unprepared condition (four plus signs on the second row) the target stimulus was presented in any one of the four character positions. The three successive

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rows of plus signs were positioned in the center of the screen and one blank line (5 mm) separated each row. The horizontal positions of the four characters of the warning signal, precue signal. and reaction stimulus directly corresponded with the four response keys. The response keys were the V. B, N, and M keys located on the bottom row of the keyboard. An index and second finger of each hand was placed on a response key. The specific horizontal presentation of a reaction stimulus, beneath one of the precued positions. elicited a key pressing response from the corresponding finger. The exact finger alignments on the response keys is shown in fig. 1 for both hand positions. RT was measured by an assembly language ms clock and it represented the delay between target stimulus onset and keyboard input (key pressing). Presentations of the warning signal (500 ms). precue signal, and target stimulus were consistent with Miller (1982: experiment 1) and Reeve and Proctor (1984: experiment 3).

Procedures

Four precued conditions were defined by the horizontal position and number of plus signs presented on the second row of the display (Miller 1982). In the no precue condition, four plus signs were presented and consequently subjects received no advance preparation information prior to the imperative target stimulus. To complete the precuing of the other three conditions two plus signs were presented in specific horizontal locations prior to the onset of the target stimulus. For instance, in the precued hand condition two plus signs were aligned with two fingers on the same hand (see fig. 1). The precued finger condition involved presenting two plus signs for homologous fingers on different hands. Nonhomologous fingers on different hands were precued with two plus signs in the neither condition.

Regardless of the position of the index fingers. a direct relationship was maintained between the presentation of the warning signal. precue signal. target stimulus. and finger response keys (Reeve and Proctor 1984; Riggio et al. 1986). However, the placement of the index fingers in an overlapped position changed the predominant left hand-right hand orientation of the response keys. That is. in the overlapped position. the index and middle fingers of the left hand were separated by the middle finger of the right hand and vice versa. Consequently, the two left-most or right-most fingers were precued in the neither condition and not in the hand condition as with the adjacent position (see fig. 1). The top hand was counterbalanced across the subjects in the overlapped position. The spatial orientation of the response keys in this study was identical to the overlapped versus adjacent orientation employed by Reeve and Proctor (1984) in experiment 3. Prior to testing. subjects read the task instructions from the monitor. finger positions were demonstrated. and any questions were answered. All subjects were instructed to respond (press the appropriate finger) as quickly and accurately as possible to the presentation of a reaction (target) stimulus. A trial sequence was as follows: (1) onset of the warning signal, (2) after 500 ms the precue signal was presented for a variable interval (no specific instructions were given on how to use the precues), (3) presentation of a single imperative reaction stimulus (one of two or four possible responses), (4) the target stimulus. precue signal, and warning signal stayed on the center of the monitor until a key pressing movement was emitted. (5) immediately following a response visual accuracy KR was presented on the screen (i.e. correct or incorrect) for 500 ms (Miller 1982). and (6) the next trial was initiated 1,000 ms after the termination of the KR. Subjects completed 800 trials per day on two consecutive days of testing. The trials were administered in 10 blocks of 80 trials with a 45 s rest interval separating consecutive blocks. The preparation of the three precue conditions was randomized across the trials within a block with the restriction that each condition have 23 trials. The 1 I no precue trials were also randomized within each block. Additionally. the four precue delay intervals of 0. 750. 1, 500. and 3.000 ms were randomly presented within a block. One test session took approximately 55 mins.

Results

ad

Discussion

The correct responses for each combination of precue delay interval and precue condition were averaged separately within each trial block. Correct response criteria were defined as depressing the appropriate key/finger elicited by the target stimulus. and a lower and an upper RT limit. Lower and upper RT limits of 120 ms and 2,000 ms were observed during the execution of the program to calculate means (after the completion of the experiment). Data beyond these two limits were considered uncharacteristic RT values (either anticipation time or nonattentive time) and were not included in mean calculations. Establishing such RT criteria was consistent with Goodman and Kelso (1980). Furthermore, preliminary comparisons across the response conditions for each trial block revealed no pronounced skewness.

J. H. Cauraugh, J. F. Horrell / Adcance prepararmr

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With the exclusion of incorrect responses and observing a lower and an upper limit on RT performance some Trial Block X Delay X Precue cell means were blank. For any blank cell the mean value of four corresponding trial block by delay by precue means within each hand position were inserted. An example will help to explain the procedure for inserting a mean value in a blank cell. For subject 1 of the adjacent hand position, the mean value of trial block 3. delay 4 (3,000 ms), and precue 4 (no precue) was blank. The blank or missing value was replaced with the means of trial blocks 1. 2. 4, and 5 for the specific combination of delay 4 by precue 4. The four included means were restricted to the same subject. Of the 5.120 mean values computed, 106 (2%) missing values were found and replaced. Alpha was set at 0.05 for each experiment. All of the reported results were statistically significant with the traditional F test and the conservative degrees of freedom adjustments (Greenhouse and Geisser 1959; Huynh and Feldt 1980; Winer 1971). The mixed design Hand Position (2) X Day (2) X Trial Block (10) X Delay (4) x Precue (4) ANOVA revealed three two-way interactions: (1) Trial Block X Delay ( F(27, 378) = 3.23, p < 0.001). (2) Delay X Precue (F(9, 126) = 20.23, p < 0.001) and (3) Precue X Hand Position (F(3, 42) = 4,26, p i 0.05). Simple main effect tests were calculated for each interaction and Tukey’s honestly significant difference (HSD) procedures were followed for mean comparisons. Fig. 2 shows the mean RTs for delay intervals as a function of trial blocks. Analysis indicated that the shortest delay interval (0 ms) was slower than the delays of 1,500 and 3,000 ms at the first and third trial blocks. For the second through the seventh blocks the shortest delay was slower than the two longest delays. At trial blocks eight, nine, and ten performance of the 0 ms delay was equivalent to the other three delay intervals.

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Over test sessions (days 1 and 2) subjects were unable to use the precued information available at the shortest delay as effectively as the longer delays. However, the advance information provided during the 0 ms delay was used to shorten RTs from the second block through the tenth. Initially, performance of the 0 ms delay was equivalent to the 750 ms delay and later the shortest delay reached the level of performance of the 1,500 and 3.000 ms delays. This finding was viewed as partial support for the effect of precuing across trial blocks. Overall, the trial block analysis provided a detailed pattern of the changes in response preparation in relation to the four manipulated delay intervals. Fig. 3 displays the Delay x Precue interaction. The precue conditions were differentiated at the three longest delay intervals. Precued hand and finger were faster than precued neither and no precue at the 750 ms delay. Again, at the shortest delay interval (0 ms) the precue conditions failed differentiation. This finding is contrary to previous studies by Miller (1982: experiment 1: prepared hand exhibited faster RTs than prepared finger or neither) and Reeve and Proctor (1984: experiment 1: prepared hand and unprepared were faster than the other two preparation conditions). For the 1,500 and 3.000 ms delays, equivalent performance was found for the three precued conditions and all three conditions were faster than no precue. The findings for the longest delay interval were consistent with Reeve and Proctor (1984). Our data support a similar conclusion: given enough precue delay time all advance information (precued hand, finger, and neither) available prior to stimulus presentation enhances response preparation of discrete finger movements. The Precue x Hand Position interaction, shown in fig. 4, answers the question: is there a difference among the three precued conditions for either hand position across extended practice? More specifically. the question was: is precued hand superior to

J. H. Cuuraugh, J. F. Hovel1 / A dwmce prepurrrtion

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neither across 1,600 trials in either hand position? Similar results were found for both hand positions; precued hand and neither exhibited equivalent performance across 1,600 trials. These findings substantiate and extend Reeve and Proctor’s (1984) experiment 3 results. For both hand positions, response fingers on the farthest left or right keys exhibited the quickest RTs. Note that in the adjacent position, the farthest left or right response fingers represented precued hand (i.e. two fingers on the same hand) and in the overlapped position, the farthest left or right response fingers represented precued neither (i.e. two different fingers on different hands). As Reeve and Proctor (1984) pointed out, the spatial relationship of the stimuli and response keys were identical in the adjacent and overlapped hand positions. If precued hand was the predominant response preparation effect as reported by Miller (1982). then realigning the finger positions should not interfere with the RT patterns across the precue conditions. However, for both hand positions, equivalent precued hand and neither findings were found. Thus, this evidence was interpreted as support for the stimulus-response translation account of response preparation. Further evidence in favor of the stimulus-response translation explanation was found in the performance of the precued fingers condition. As shown in fig. 4, for both the adjacent and overlapped hand positions, precued fingers were equivalent to precued hand and neither conditions. Again. preliminary information about response fingers on different hands enhanced RT performance while an extensive amount of practice was completed. This finding is contrary to (a) Miller’s (1982) prepared hand advantage based on 400 test trials and (b) the motoric account of response preparation effects (Miller 1985; Reeve and Proctor 1985a). The critical implication of these results is that with extended practice stimulus-response translation processes accounts for response preparation effects. precued

J. H. Caurough. J. F. Horrell / Admtm

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of correct responses

Pewentage

An additional mixed design, trial block analysis was conducted on the percentage of correct responses. The 2 X 2 X 10 X 4 X 4 (Hand Position X Day X Trial Block X Delay x Precue) ANOVA identified two significant two-way interactions: (1) Delay X Precue (F(9, 126) = 4.35, p < 0.001) and (2) Precue x Hand Position (F(3, 42) = 4.78. p < 0.01). Fig. 5 shows the differentiated precue conditions on the percentage of correct responses at two delay intervals: 0 ms and 1,500 ms. For the shortest delay, precued hand and no precue displayed higher percentages than precued finger. Additionally.

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J. H. Cauraugh. J. F. Horrell / Advance preparution

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performance of the no precue condition exceeded precued neither. At the 1,500 ms delay the three precued conditions showed higher percentages of correct responses than the no precue condition. The Precue x Hand Position interaction (see fig. 6) revealed an adjacent position higher percentage at precued hand vs. precued neither. However. this advantage was not found in the overlapped hand position. This pattern of results in the percentage of correct responses was not found in previous studies (Proctor and Reeve 1986: Reeve and Proctor 1984) and not discussed by Miller (1985). The critical contribution of the accuracy pattern for response preparation is that it parallels mean RT findings of the present study and Reeve and Proctor (1984: experiment 3). That is, equivalent percentages of accurate responses were found at precued hand and neither for the overlapped position, whereas in the adjacent position precued hand was superior. Also a significant trial block main effect was found (F(9, 126) = 7.22. p < 0.001). Post-hoc analysis indicated higher percentages of correct responses (95%, 96%. or 97%,) for trial blocks 3, 4, 6, 7. 8. 9. and 10 in comparison to trial block 1 (M = 920/c, SD = 5.5). Also, the last trial block (M = 97%, SD = 2.9) displayed more accurate responses than the second (M = 94%. SD = 3.1) and fifth (M = 94%. SD = 4.9) blocks.

Experiment

2

Results of the first experiment supplement our information about the decision making process involved in response preparation of discrete finger movements. That is, the overall pattern of RTs for both precued hand and precued neither are similar across extended practice (1.600 trials of training). The first experiment also revealed that across extended practice the trial block factor interacted with the delay factor. This interaction upholds the valuable contribution of a mean RT trial blocks analysis. The primary purpose of experiment 2 was to determine the response preparation performance of three hand positions simultaneously. As discussed in the Introduction the horizontal alignment of the response fingers tested by Reeve and Proctor (1984: experiment 3) has been questioned by Miller (1985). If a different response set is used in the overlapped position as Miller argued then slower RTs for a side advantage should again be found in comparison to precued hand in the adjacent condition. The new hand position, referred to as crossed index fingers, was not as far removed from the adjacent position as the overlapped condition (Cauraugh 1987). This more neutral position still maintained the spatial compatibility of the overlapped condition (i.e. the two left- or right-most fingers were on different hands). Mean RT comparisons across the three hand positions produced more information on the motoric versus nonmotoric debate. Experiment 2 tested the hand positions of adjacent, crossed, and overlapped as a between subjects factor and the three within subjects factors were trial blocks (4). delays (5) and precues (4). Method Subjects Thirty-nine university graduate students volunteered to participate in exchange for experimental credit in a motor learning or kinesiology class. Each hand position group

was composed of six females and seven males. The subjects here naive as to the purpose and procedures of the experiment. Two subjects were replaced because they continually depressed the response keys prior to stimulus presentation for the longest delay interval.

The same microcomputer hardware used in the first experiment was also used in this experiment. The microcomputer was programmed to control the experiment and collect finger, keypressing RT data. Consistent with previous experiments, the standard plus sign character was used to present the warning signal. precue signal. and target stimulus on three rows in the center of the monitor. Two changes were made in the computer program. Instead of presenting 80 trials per block. 140 trials were presented (see Procedures). Also the number of delay intervals was expanded to five. These intervals (0. 375. 750, 1.500, and 3,000 ms) were the same five tested by Reeve and Proctor (19X4) in experiments 1 and 3. Procedures

Subjects were randomly assigned to one of three hand positions: (a) adjacent, (h) crossed. or (c) overlapped. The adjacent and overlapped hand positions were the same positions tested in experiment 1 and were consistent with Reeve and Proctor’s (1984) third experiment. The crossed index fingers condition was a new hand position which represented the same spatial alignment as the overlapped condition (Riggio et al. 1986). That is. the two fingers on the farthest left or right were fingers on different hands. Fig. 7 shows the three hand positions for the precued hand and neither conditions. For the overlapped and crossed positions, the top hand was counterbalanced across subjects. Briefly. the index and middle fingers of each hand were positioned on four centered keys on the bottom row of the keyboard. The three precued conditions (hand. finger, and neither) were represented by two plus signs aligned in different horizontal positions on the second row of the display. The no precue condition consisted of a plus sign presented in each of the four finger positions. Upon arrival to an isolated testing room in the motor behavior laboratory subjects sat in front of the computer monitor to read the task’s directions. As in the previous experiment. the monitor was located at eye level. approximately 50 cm away. The specific hand position was demonstrated during the directions. All subjects completed 30 practice trials prior to testing (Miller 1982, 1985; Reeve and Proctor 1984, 1985b). Any subjects questions were answered before testing began. All possible combinations of precue conditions, delay intervals. and target stimulus positions were presented randomly in each of the four blocks of 140 trials. The three precued conditions were tested 40 times in a block. Of the 40 randomly presented trials, 20 were presented to the left hand and 20 to the right hand. The 20 trials were divided equally among the five delay intervals: 0, 375. 750, 1,500. and 3.000 ms. Both the index and middle fingers were tested on two trials at each delay for each hand. The no precue condition was tested 20 times in a block. ten trials to each hand and one trial of each delay interval to each finger. Consistent with the first experiment, subjects received visual KR (for 500 ms) concerning the accuracy of their finger response and 1,000 ms elapsed before the start

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of the next trial. Each subject was administered 560 test trials without a rest period between trial blocks. The procedure of no rest periods across the experiment is consistent with previous response preparation studies (Miller 1982, 1983, 1985; Proctor and Reeve 1985; Reeve and Proctor 1984, 1985b). The present testing session took approximately 35 min.

Results und Discussion

Reaction

time performance

Mean correct RTs were computed for each trial block, delay interval, and precue condition. As in the first experiment lower and upper limits on RTs were observed. In the second experiment, no dramatic departure from symmetry was observed and the mean calculation procedure failed to produce any missing values. Mean trial block RTs were analyzed in a four factor mixed design - Hand Position (3) X Trial Block (4) X Delay (5) x Precue (4). The ANOVA revealed three significant two-way interactions. Again, follow-up tests involved simple main effect tests and Tukey’s HSD mean comparisons.

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The first significant interaction was Trial Block X Delay (F(12, 432) = 2.94, p < 0.001). As seen in fig. 8 trial blocks 3 and 4 were differentiated from the first two blocks at 0 ms delay. Performance efficiency reflected in enhanced RTs, increased across the trial blocks for the shortest delay. The RT advantage for the last two trial blocks was not found at the other four delay intervals. These results are similar to the trial block by delay interaction found in experiment 1. Taken together. both interactions show that performance at the shortest precue delay (0 ms) improves over time. The trial blocks findings of the present experiment suggests that even for precue delays of less than 1,000 ms (e.g. 375 ms and 750 ms) RTs were facilitated in comparison to the shortest delay (0 ms). The trial block by delay interactions of experiments 1 and 2 are new findings. This new information about the delay intervals reveals the changes in performance that take place from the beginning to the end of a test session. The trial block analyses revealed changes in the general preparation effect that is typically found with variable delay intervals (Sanders 1980)’ Furthermore, without the trial block analysis the nature of change that subjects experienced at the delay intervals of less than 1.000 ms would go unknown. Precue X Hand Position (F(6, 108) = 2.47. Fig. 9 displays the second interaction, the most important finding of this p i 0.05). In terms of response preparation, interaction was the performance of precued hand and neither within each of the three hand positions. Follow-up analysis indicated that a precued hand advantage found in the adjacent position failed significance in the crossed and overlapped positions. More precisely, the precued neither condition exhibited equivalent performance RTs as ’ Appreciation is extended tc an anonymous reviewer

for

pointing this out

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hand in both the crossed and overlapped positions. The equivalent performance of precued hand and neither for the crossed and overlapped conditions replicates and extends the findings of Reeve and Proctor (1984: experiment 3). The replication consists of the lack of differentiated performance for precued hand (fingers on the same hand) and precued neither (fingers on different hands) in the overlapped hand position. The extension involves the same findings for the index fingers crossed hand position; precued fingers on the same hand were equal to precued fingers on different hands. These results reveal that precued information about fingers on the farthest left or right facilitates performance regardless of the hand or hands involved. These findings and interpretations of motoric versus nonmotoric support are elaborated in the General Discussion. The Delay x Precue interaction illustrated in fig. 10 was the third significant two-way interaction (F(12, 432) = 16.87, p -C0.001). For the two shortest precue delays, 0 ms and 375 ms, the type and amount of precue information failed to differentiate mean RT performance. This finding fails to replicate Miller (1982: experiment 1) or Reeve and Proctor (1984: experiments 1 and 3). Over 560 trials no advantage for any of the three precued conditions or the no precue condition was found at the two shortest delay intervals. At the 750 ms delay, precued hand and neither conditions displayed faster response preparation than the no precue condition. With the three tested hand positions of the present experiment, it is not surprising that a distinct hand advantage was not found at the 750 ms delay. The hand advantage found in previous studies (Miller 1982, 1985; Reeve and Proctor 1984) most likely resulted from the adjacent hand placement. As reported in the precue by hand position interaction, precued hand does not always perform the best across hand positions. In the crossed and overlapped positions equivalent performance was found in the precued neither conditions.

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J.H. c‘aurcrugh. J. F. Horrrll

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For the two longest precue delays. 1 SO0 ms and 3.000 ms, precued hand, finger, and neither conditions all completed the discrete finger key presses faster than no precue. These enhanced RT results for the three precued conditions at delay intervals longer than 1 s are consistent with those reported by Reeve and Proctor (1984). This finding was also found in experiment 1. These findings are further discussed in the General Discussion. Two points about these results should be noted. First, any type of advance information, which reduces the number of response choices from four to two, should facilitate RT performance in comparison to no advance information. However, only at the two longest delays did each type of preliminary (precued) information (hand. finger, and neither) perform better than the no precue. At the 750 ms delay no precue performance was equivalent to precued finger. Additionally. no performance differences in precue type vs. no precue were found at the two shortest delays. For the three tested hand positions. the simultaneous or near simultaneous presentation of a precue signal and imperative stimulus seems to eliminate the inherent advantage of the precue or preliminary information. Perhaps the different response finger placements contributed to this finding. The second point concerns the equivalent performance of the precued hand, finger, and neither conditions across the delay periods. The lack of a precued hand advantage conflicts with Miller’s (1982: experiment 1) findings. As mentioned earlier, the precue by hand position interaction is a viable explanation. In the adjacent condition, precued hand facilitated performance, however. in the crossed and overlapped positions precued neither achieved comparable performance. This point is further elaborated on in the General Discussion.

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Percentage of correct responses Analysis of the mean percentages of correct responses revealed a trial blocks main effect (F(3, 108) = 10.58, p < 0.001). Tukey’s HSD procedure showed higher percentages in the third and fourth trial blocks (MS = 97%, 97%, SDS = 1.3. 1.0) than in the first block (M = 95%, SD = 1.5). Response accuracy increased across the 560 trials. The analysis also revealed a significant Delay X Hand Position interaction (F(8, 144) = 3.71, p < 0.01). As seen in fig. 11, higher percentages of accurate responses were found in the adjacent and crossed hand positions than in the overlapped position at each delay except the shortest interval (0 ms). No difference was found at 0 ms delay between crossed and overlapped. Also, the adjacent performance was better than the crossed performance at 0 and 3,000 ms delays.

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.I. H. Cauraugh, J. F. Horrell / Admmcr preporutron

Fig. 12 shows the mean percentage of correct responses for precue conditions as a function of delay intervals (F(12, 432) = 3.27, p < 0.001). Follow-up analysis indicated superior performance by the no precue condition versus precued finger and neither at the two shortest delay intervals (0 and 375 ms). At the longest delay (3,000 ma) though the results were reversed; the three precued conditions displayed higher mean accuracy than the no precue condition.

General discussion The extended practice results of experiment 1 has helped to resolve the nonmotoric versus motoric explanations of advance preparation. The different predictions of the two explanations were tested and the nonmotoric prediction was upheld. Equivalent RT performances were found for both the adjacent and overlapped hand positions regardless of the precued conditions (hand, finger or neither). The above finding is consistent with the stimulus-response translation account and the results of Reeve and Proctor (1984: experiment 3). Across 1,600 trials of practice, precued information about the two left-most or right-most fingers facilitated performance. In the overlapped hand position, the two left-most and right-most fingers represented a finger from each hand in the precued neither condition. Such a finding is incongruent with the motoric explanation in which precued hand (i.e. fingers on the same hand) supposedly has an inherent advantage. Additional conflict with the motoric explanation is found in the equivalent performance of the precued hand, finger, and neither conditions found in experiment 1. This finding, which is consistent across both hand positions, indicates that over 1,600 trials of practice the same fingers on different hands are readily prepared as other precued conditions. The reason that this finding conflicts with the motoric account of movement parameter preparation is that the differences in performances of the precued conditions failed to persist with practice. That is, the advantage of precuing two fingers on the same hand (Miller 1982: experiment 1 ~ 400 trials) was eliminated over 1,600 trials of performance. This result supports the Reeve and Proctor (1984) argument that differential processing of the stimulus cues accounts for enhanced advance preparation. Other evidence supporting the stimulus-response translation account was found in the results of the percentage of correct responses. In

J. H. C’auruugh, .I. F. Horreli / Adrwnce preparation

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experiment 1, the precue by hand position interaction shows that an accuracy advantage for the adjacent position for precued hand (in comparison to precued neither) is not found for the overlapped position. The equivalent performance across the overlapped position indicates that with practice two fingers on different hands, which spatially represent fingers on the farthest left and right (response keys and stimuli positions), are as accurate as fingers on the same hands. Moreover, the finding of similar mean RT performance for the three precued conditions bears directly on Miller’s (1985) criticism of Reeve and Proctor’s (1984) translation account. Miller (1985: 226) argued that the ‘lack of preparation effects in prepared: finger and prepared: neither conditions’ was difficult for the stimulus-response translation account to explain. However, the present results indicate that each of the three precued conditions excelled in comparison to the no precue condition. The implication being that a consistent pattern for responding was established across the 1,600 trials. Additionally, these findings are in line with the processing of stimulus cues explanation for response preparation (Larish 1986; Proctor and Reeve 1986; Reeve and Proctor 1985a; Welford 1968). The Precue X Hand Position interaction found in experiment 2 is also interpreted as nonmotoric support. The specific reason for concluding that the response preparation effect found for precued hand involves stimulus-response translation processes is the equivalent precued hand, finger, and neither performances found in the crossed and overlapped hand positions. An advantage for precued hand in the adjacent condition failed to be found in the crossed and overlapped positions. The argument that there is a motoric advantage for the precued hand condition can be discounted because the RT differences in the precued conditions which should persist with an increased number of trials, were not found. When subjects complete 560 trials and most certainly across 1,600 trials the similarity in the precued conditions can be attributed to the less stimulus-response translation time required (Teichner and Krebs 1974; Welford 1968). Furthermore, the present results provide evidence refuting Miller’s (1985) notion of different types of processing. Miller (1985) reasoned that Reeve and Proctor’s (1984) large differences in RT performance (222 ms) between adjacent and overlapped hand positions constituted two different types of response preparation. One type was a hand advantage, motoric response preparation. The second type proposed by Miller was a

slower, more deliberate type of preparation in which the hand advantage was not readily available and a side advantage prevailed. Such an argument is weakened by the mean RT performances of the adjacent and overlapped hand positions in the present study. The RT performance differences between the two hand positions are relatively small in both Experiments 1 and 2 (68 ms and 72 ms, respectively). These results show that the increase in the number of test trials to 1,600 or 560 from Reeve and Proctor’s (1984) 280 trials enhanced the performance of the overlapped hand positions. More specifically. the performance of the two hand position groups fails to support two types of response preparation. As stated earlier, precued information about two fingers facilitates advance preparation regardless of the hands involved. An additional point concerns the precue delay intervals and response preparation. Each of the two present experiments found reliable Delay x Precue interactions. For delay intervals longer than 1,000 or 1.500 ms the precued or prepared conditions performed the two-choice RT task in an equivalent manner. This evidence replicates the delay by precue findings of Reeve and Proctor (1984: experiments 1 and 3). When subjects are given enough time to prepare (i.e. more than 1,000 ms) all advance information about the forthcoming response facilitates mean RT performance (Goodman and Kelso 1980). Our interpretation of response preparation results, in light of the present delay interval by precue condition evidence, echoes Reeve and Proctor’s (1984) concern. That is, response preparation conclusions based on precue delay intervals or inter-stimulus intervals of less than 1,000 ms should be interpreted cautiously. In conclusion, the reported experiments investigated advance preparation processes using a movement precuing procedure. That is, the temporal durations for assigning or specifying finger parameters on the same hand and different hands were examined in a choice RT task with advance information manipulated. This type of motor programming research has expanded our knowledge about the temporal sequence of events that occur prior to movement initiation (Keele 1981; Rosenbaum 1983; Zelaznik and Larish 1986). Specifically, the mean RT results of experiments 1 and 2 provide evidence supporting a stimulussresponse translation explanation of advance preparation/motor programming.

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