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Binary choice reaction time as a criterion of motor equivalence
Acta Psychologica 50 (1982) 35-47 North-Holland Publishing Company
BINARY CHOICE REACTION MOTOR EQUIVALENCE * Herbert
35
TIME AS A CRITERION
OF
HEUER
University of Diisseldorf, W. Germany
Accepted April 1981
In a binary choice situation the two alternative movements may vary in the degree in which they are equivalent in respect to controlling processes and/or structures. With a higher degree of motor equivalence a shorter RT is to be expected. A series of five experiments shows that a movement of a finger of one hand has a shorter latency if the alternative movement with the other hand is of the same form than in case of different forms. There is no evidence of a corresponding effect of using the same or different fingers with both hands. These results indicate that programming of the form of a movement is at least partly independent of the muscles involved in movement execution.
Introduction Since the pioneering work of Henry and Rogers (1960) a number of experiments has demonstrated that RT depends on certain physical characteristics of the response (for reviews see Klapp 1977a; Kerr 1978; Marieniuk and MacKenzie 1980; Henry 1980), but only few experiments were devoted to the effects of the relationship between the physical characteristics of the alternative responses in a choice situation. These experiments bear on the problem of motor equivalence. The term “motor equivalence” is intended to refer to the similarity or overlap of the processes and/or structures involved in the control of different movements. It may be given a more specific meaning in the context of two different but not incompatible conceptualizations of motor control.
* Mailing address: Herbert Heuer, UniversitLt Diisseldorf, Psychologisches Institut, Universitltsstrasse 1, D-4000 Diisseldorf 1, W. Germany
000 1-69 1S/82/0000-0000/$02.75
0 1982 North-Holland
36
H. Heuer /Binary
choice reaction time: I
The concept of a motor program is now in widespread use. According to Schmidt (1975) a motor program controls a certain class of movements. Which movement of the class is executed depends on additional specifications or parameters. Therefore, different movements may differ in the program or in a certain number of parameters and will be correspondingly more or less equivalent. The second conceptualization was introduced by Rosenbaum (1977). The basic suggestion is that certain physical characteristics of a movement may be determined by the activity of a certain group of specific neurons. These hypothetical neural structures are analogous to the feature detectors of the visual system. Different movements may involve identical structures to a varying degree, and this structural overlap then defines the degree of motor equivalence in this context. The general expectation is that choice RT will be shorter if the response alternatives show a higher degree of motor equivalence. For example Megaw (1972) interpreted the shorter RTs in case of movement extent uncertainty than in case of direction uncertainty as indicating that the same motor program is involved in the control of movements which differ in amplitude, but different programs in the control of movements in different directions. In a similar way Rosenbaum (1978; 1980) demonstrated the relationship of choice RT to the number of identical parameters of the response alternatives. The expectation of a relationship between the degree of motor equivalence and choice RT implies certain assumptions about the preparation before the imperative signal. If subjects prepare what is common to the responses (“conjunctive preparation”) movements of higher equivalence will be prepared more than less equivalent movements and therefore the RT will be faster. The same is to be expected under the assumption of “single preparation” where subjects prepare only one of the response alternatives, but depending on the degree of motor equivalence the shift to the unprepared response will take more or less time (see Semjen et al. 1978; Requin 1980). In contrast, no relationship will exist if there is “multiple preparation” where subjects prepare both responses completely (Rosenbaum 1980). Up to now we have considered choice RT as being dependent on the degree of motor equivalence. This hypothesis of course cannot be verified because the degree of motor equivalence can only be varied via the relationship between the physical characteristics of the alternative responses, and there need not be any simple relation between physical
H. Heuer /Binary
choice reaction time: I
37
similarity and the similarity or overlap of the underlying control processes. Therefore, it is preferable to consider choice RT as a criterion of motor equivalence. This means to presuppose a relationship between choice RT and the degree of motor equivalence, but the validity of this supposition can be examined by a comparison of different criteria. At least three other criteria of motor equivalence have been suggested which were derived from one or the other of the two conceptualizations mentioned above. In general, they are based on after-effects which one movement has on the execution of another movement, larger after-effects being taken as indication of a higher degree of motor equivalence: (1) Contralateral effects of fast movements performed with one hand for a certain time on speed and variability of movements performed with the other hand afterwards (Rosenbaum 1977; Rosenbaum and Radford 1977; Heuer 1980, in press) (2) effects of different movements on the acceleration pattern of a following movement (Heuer 1979) (3) sequential effects in RT experiments (van Galen 1980) It is obviously desirable to explore the relations between the different techniques, which are all intended to give indications of the degree of motor equivalence but which will certainly each have its own peculiarities. The present experiments were designed as a first step in this direction. Heuer ( 1980, in press) used the “selective fatigue” technique introduced by Rosenbaum (1977) and Rosenbaum and Radford (1977) to test the differences in the degree of motor equivalence between pairs of movements which were varied in respect to form and muscles involved. Subjects had to perform tapping movements with the index finger of the right hand as fast as possible for a period of 30 sec. Just before this test period they performed one of four different movements with the left hand for 30 sec. These movements differed from the test movement with the right hand in respect to form and/or muscles involved. They were performed with the index finger or the thumb, and their form was tapping or alternating. While tapping is a simple up-and-down movement, alternating is mainly a horizontal movement with only a small vertical component. The results were a heightened variability of the movement times if
H. Heuer /Binary
38
choice reaction time: I
the foregoing movements were of identical form (form effect) or if homologous muscles were involved (muscle effect) relative to different forms or non-homologous muscles. This was taken as evidence for a reduced degree of motor equivalence if the form of the movements is different or the muscles involved are non-homologous. From these results one should expect a form effect and a muscle effect in a choice RT experiment using the same movements with shorter RTs in case of identical forms or homologous muscles.
The experiment Method Subjects
There were 50 female Ss in total, ranging ln age from 16 to 29 years. In each experiment 10 Ss participated. They were paid a fixed amount of money, independent of performance. Experiments
The five experiments differed in the movement with the right hand, which was the same for all conditions in one experiment and which will be referred to as criterion movement in the following. The different criterion movements are listed in table 1. They will be used to refer to the different experiments. Different criterion movements were used to make sure that any effects observed are due to the relation between the criterion movement and the alternative movement with the left hand and not just to the specific kind of movement used as alternative. As shown in table 1, alternating with the index finger was used twice as a criterion movement. In exp. AI/S alternating movements with the left hand were symmetrical to the alternating movements with the right hand, in exp. AI/D alter-
Table 1 Criterion movements in the five experiments. Exp.
Criterion movement
Abbreviation
I II III IV V
Tapping, Index finger Tapping, Thumb Alternating, Index finger Alternating, Index finger Alternating, Thumb
TI TT AI/S a) AI/D a) AT
a) Alternating movements with both hands were Symmetrical (AI/S) or in the same Direction (AI/D)
H. Heuer /Binary choice reaction time: I
nating movements the left. Experimental
with both hands were of the same direction,
39
always starting to
conditions
Four conditions were run in each experiment. The conditions will be labelled either by the specific alternative movement involved or by the relation of the alternative to the criterion movement: F=/M= (form equal/muscles homologous), F=/Mf (form equal/muscles non-homologous), F#/M= (form different/muscles homologous) and Ff/Mf (form different/muscles non-homologous). Apparatus
The movements were performed with the same apparatus that was used by Heuer (1980, in press) in the selective fatigue experiments. The Ss grasped horizontally mounted handles with each hand, which were about 40 cm laterally apart and about 4 cm above table top. The height was adjusted so that the Ss could comfortably reach a black button with their stretched index finger or another black button with their laterally stretched thumb. In the case of tapping a steel wire was attached by means of adhesive tape near the base of the finger nail. This steel wire rotated around its pivot when the S lifted her finger and activated a switch as soon as the finger reached a height of approximately 5 cm. As soon as the S lifted her finger, again when she reached the defined height, and a third time when she depressed the black button, she heard a tone of 30 msec duration. In 2.5 cm distance in the direction towards the median plane of the S there was another button of orange colour (for the thumb this orange button was only slightly displaced towards the median plane but more towards the S). In performing alternating movements, the Ss had to lift their finger from the black button, depress the orange one and again the black one. At each occasion they heard the short tone. For exp. AI/D and AT the orange and black button were interchanged for the left hand. Thus, the orange button was always to the left of the black one. Between the two buttons there was a small barrier which forced the movements to reach a minimum height of approximately 0.5 cm. ‘In front of the Ss, at a distance of about 10 cm from the buttons, there were three stimulus lights. A green one of 5 mm diameter in the middle served as a warning signal. The imperative signals were two red light-emitting diodes of 2 mm diameter at a distance of 2 cm to the left and to the right of the warning signal. The whole experiment was controlled by a microcomputer. Design and procedure
Each S took part in six sessions on consecutive days (with a few exceptions). A session comprised four blocks of trials with breaks of 5- 10 mm between blocks, each block with a certain movement combination according to the different conditions. Over the last four sessions the conditions were arranged in a latin square for each S. The first two sessions were for training. They were identical with the last two sessions. Each block consisted of 110 trials, the first 10 again for training. Of the last 100 trials, 50 called for a response with the left hand and 50 for a response with the right one in a random order.
40
H. Heuer /Binary choice reaction time: I
A trial was initiated by S when she shortly lifted one of her fingers and pressed the black button again. After a period of 1 set the warning signal .was presented, which remained on for 2 sec. If the S started a movement during this period, or more exactly, if she lifted one of the two fingers from the black button, the trial was interrupted and had to be initiated again. With the end of the foreperiod the imperative signal was presented and remained on until the end of the correct movement. Two kinds of errors were recorded. In case of a choice error the S lifted the wrong finger from the black button, in case of an execution error either a tapping movement did not reach the required height or the orange button was not depressed with an alternating movement. All trials in which an error occurred were repeated at the end of each block. At the beginning of the first session the Ss were made familiar with the movements required. The instruction demanded for fast and correct movements. Dependent variables For each trial the reaction time and the movement time were measured. The reaction time interval lasted from the presentation of the imperative signal until the S lifted her finger from the correct black button. The movement time interval started with the end of the reaction time interval and was finished when S depressed the black button again. For each S and each alternative in each condition there were 200 measurements in total. The analysis is based on the mean and the standard deviation of these measurements. Reaction times outside the range from 1.50 to 1000 msec and movement times larger than 1500 msec were neglected. Results R T for the criterion movements The mean RTs and the mean standard deviations for all five experiments are presented in fig. 1 as a function of the specific alternative movement. In all five experiments the RT is smaller when the alternative movement is of the same form as the criterion movement. In the two experiments with tapping as criterion movement it is smaller with tapping as alternative, in the experiments using alternating as criterion movement with alternating. The data were analysed by mean of a fixed-effects ANOVA (BMDP2V). The effect of the form relation is significant in all experiments except exp. TT (TI: F( 1,9) = 39.74, p < 0.01; TT: F( 1,9) = 3.94, p < 0.10; AI/S: F(1,9) = 5.12, p < 0.05; AI/D: F(1,9) = 8.61, p < 0.05; AT: F(1,9) = 23.72, p < 0.01). The mean standard deviations show the same pattern, but it is not as distinct as with the mean RTs. The effect of the form relation is present in all experiments, but significant only in three of them (TI: F( 1,9) = 17.67, p < 0.01; AI/D: F( 1,9) = 11.12,p<0.05;AT:F(1,9)=7.43,p<0.05). In contrast to the consistent effects of the form relation the muscle relation shows a significant effect only in exp. AI/S (F( 1,9) = 12.63, p < 0.01). Here the reaction time is shorter when both movements are performed with the same finger of each hand. In the other four experiments the effect is not significant and in exp. TT it is even in the wrong direction.
H. Heuer /Binary
choice reaction time: I
41
Fig. 1. Mean RTs and mean standard deviations for the criterion movements (right hand).
The effect of the muscle relation on the standard deviations is in none of the five experiments significant. Its direction is always the same as the effect on the mean RTs. The interaction of form and muscle relation is never significant. R T for the alternative
movements
The criterion movements are identical for all four conditions of each experiment, and the differences between conditions can be unequivocally attributed to the different alternative movements. The RTs for the alternative movements should again depend on the relation to the criterion movements, but a second factor is of importance, because the alternative movements differ across conditions. The RTs will
42
Fig. 2. Mean RTs for the alternative movements (left hand).
therefore show the combined effects of the latencies with the different movements in isolation, which might reflect differences in programming times, and the relation between the response alternatives. The mean RTs are presented in fig. 2. The most obvious fact from fig. 2 is that the differences between different alternative movements reflect mainly the differences in the relation to the criterion movement. In the first two experiments the RTs are significantly shorter with tapping than with alternating (TI: F( 1,9) = 10.76, p < 0.01; TT: F( 1,9) = 46.94, p < O.Ol), but in the other three experiments they are slightly shorter with alternating although these differences are not significant. Similar effects are to be found with the mean standard deviations. In the first two experiments they are smaller with tapping (TI: F(1,9) = 3.99, p < 0.10; TT: F(1,9) = 8.49, p < 0.05), and in the other experiments there are no significant effects of the form relation. The effect of the muscles involved is significant in all experiments except exp. TT. The RT is shorter with movements of the thumb than with movements of the index finger in exp. TI (F( 1,9) = 23.18, p < 0.01) and AI/S (F( 1,9) = 6.86, p < 0.05), but longer in exp. AI/D (F( 1,9> = 8.99, p < 0.05) and AT (F( 1,9) = 28.21, p < 0.05). These effects show no consistent relation either to the specific finger used for the alternative movement nor to its relation to the finger used for the criterion movement: in exp. TI, AI/S and AT the mean RT is significantly shorter when different fingers are used, but in exp. AI/D it is shorter with identical fingers of both hands. With the standard deviation there is a significant effect of the muscle relation only in exp. AT (F( 1,9) = 5.58, p < 0.05), which parallels the effect found for the mean RT. This parallelity does not hold for all of the other experiments. A significant interaction between form and muscle relation again does not show up in any of the experiments.
43
Fig. 3. Mean MTs for the criterion movements (right hand).
MT for criterion
movements
The mean movement times are presented in fig. 3. The MT is always longer with alternating as the alternative movement. This effect, which is obviously due to the specific alternative but not to the relation between the two movements, is significant in allexperiments except exp. AI/D (TI: F(1,9)= 7.41, p < O.OS;TT: F(1,9) = 8.68,p<0.05,AI/S:F(1,9)=17.01,p
errors
The number of choice errors was determined for each S and each condition. In a first analysis erroneous responses to both signals were collapsed and the existence of an effect of the form relation or the muscle relation was tested by means of a simple binomial sign test (Dixon and Mood 1946). In none of the five experiments there was a significant muscle effect, and only in exp. AI/D the form effect was significant: 8 out of 10 Ss showed more errors with response alternatives of equal form and only one S with alternatives of different form (means: 3.60 vs 2.55). In the other experiments the differences were negligible, ranging from 0 to 0.35, but never being of negative sign. In a second analysis the differences in the number of errors to both signals were
H. Heuer /Binary
44
choice reaction time: I
taken into consideration. This was done as a test for biases in favour of one or the other of the response alternatives which might be different in different conditions. According to results by Fitts et al. (1963) this kind of bias would be indicated by a shorter RT and a smaller number of errors in response to the favoured signal. Again, there was no muscle effect, but the form effect was significant in three experiments. In these experiments (TI, AI/D, AT) there was a bias towards less errors in response to the right signal in conditions with response alternatives of identical form, and with alternatives of different form there were fewer errors in response to the left signal. In the two other experiments (TT and AI/S) this pattern was not observed, but there were always less errors in response to the right signal, and in the conditions with alternatives of different form this tendency was even stronger than in equal form conditions, although not significantly so. Execution
errors
Execution errors were analysed only for the criterion movements with the right hand. In case of alternating they were very rare events (less then 0.2%), but in case of tapping their frequency was higher. In both of the two experiments with tapping as the criterion movement (TI and TT) they were significantly more frequent when the alternative movement was of the same form (sign test), and in exp. TT they were more frequent with response alternatives involving non-homologous muscles than in case of homologous ones, while in exp. TI the muscle effect was non-significant.
Discussion In all five experiments there is a consistent effect of the form of the alternative movement: the binary choice RT with a certain movement is smaller when the alternative movement with the other hand is of the same form than with an alternative of a different form. This effect can be unequivocally attributed to the form relation. The difference in the mean RT is paralleled by a difference in the mean variability of the RTs. Contrary to expectation there is no consistent effect of the muscle relation. This kind of effect appeared only in one experiment and is probably a chance result. These results on RT show no consistent relation to the pattern of results obtained with the movement times. While reaction times depend on the relation between the response alternatives, movement times depend on the specific alternative. Thus, the RT effects cannot be considered as being secondary to MT effects. We are inclined to reject any interpretation of the observed form effect as being an artefact due to speed-accuracy tradeoff, although in
H. Heuer /Binary
choice reaction time: I
45
case of significant differences execution or choice errors are of higher frequency in conditions with response alternatives of identical form. There are two reasons for our rejection. Firstly, a significant form effect in respect to execution errors was observed in only two experiments, but in the three other experiments a significant RT effect was observed without a corresponding effect in the number of execution errors. A similar argument holds for the form effect in respect to choice errors. The second reason pertains to choice errors only. An inverse relation between RT and error frequency is not necessarily due to different accuracy criteria which Ss adopt for one or the other reason. It could as well be explained by differences in the degree of motor equivalence which make confusions more or less likely. There is another effect observed with the number of choice errors which could be taken as a basis for an interpretation of the RT results. According to differences in the error frequencies in response to the two signals subjects favour the right one in equal form conditions but the left one in conditions with unequal form in three of the experiments, This could explain the form effect observed with the RTs to the right signal which was the signal’demanding for the criterion movement. But if this interpretation were valid the RTs with the left hand should differ in the opposite direction, being larger in equal form conditions and smaller if the response alternatives are of different form. Since the latencies of the alternative movements show the same effect as the latencies of the criterion movements this interpretation can be rejected. In our opinion there is good reason to take the effect of the form relation on RT as an indicator of a higher degree of motor equivalence of movements of identical form, which are performed with different hands or even with different fingers of different hands. Thus, programming of the form of a movement is not inherently linked to the use of certain muscles. This is a corrobation of Klapp’s (1977b) conclusion which was based on a different experimental procedure. Contrary to expectation there was no muscle effect. This is obviously not in line with the results obtained with another criterion of motor equivalence, namely the contralateral transfer technique (Heuer 1980, in press). At present only one conclusion can be drawn from this inconsistency: there are factors specific to the different techniques which may under certain conditions result in “false positive” or “false negative” results. Although the main concern of this series of experiments is the effect
46
H. Heuer /Binary
choice reaction time: I
of different alternative movements with the left hand on the latencies of identical criterion movements with the right hand, the left hand RTs deserve some comment. These results bear on the problem of whether choice RTs or simple RTs are to be preferred for the study of motor programming times (see Klapp 1977a; Klapp et al. 1974; Klapp et al. 1979; Sternberg et al. 1978). Assume that the programming time for tapping is somewhat smaller than that for alternating. In a choice situation this difference will in most cases be contaminated by differences which are due to the relation between the movements under study. In the first two experiments of our series with tapping as the criterion movement the basic difference was enhanced. In these experiments the RT for tapping was significantly shorter than that for alternating. Contrary to this the RT difference between tapping and alternating was reversed in the three experiments with alternating as the criterion movement, although not significantly so. Here the form relation favours alternating. It might be hard to obtain RT measurements with different movements in a choice situation which are not contaminated by effects of the relationship between the two response alternatives.
References Dixon, W.J. and A.M. Mood, 1946. The statistical sign test. Journal of the American Statistical Association 41, 557-566. Fitts, P.M., J.R. Peterson and G. Wolpe, 1963. Cognitive aspects of information processing: 11. Adjustments to stimulus redundacy. Journal of Experimental Psychology 65,423-432. GaIen, G.P. van, 1980. ‘Handwriting and drawing: a two-stage model of complex motor behavior’. In: G.E. Stelmach and J. Requin (eds.), Tutorials in motor behavior. Amsterdam: North-Holland. Henry, F.M., 1980. Use of simple reaction time in motor programming studies: a reply to KIapp, Wyatt and Lingo. Journal of Motor Behavior 12, 163-168. Henry, F.M. and D.E. Rogers, 1960. Increased response latency for complicated movements and a ‘memory-drum’ theory of neuromotor reaction. Research Quarterly 31,448-458. Heuer, H., 1979. Uber Bewegungsprogramme bei willkiirlichen Bewegungen. Berichte aus den Fachbereich Psychologie der Phillipps-Universitat, Marburg/Lahn, Nr. 76. Heuer, H., 1980. Selective fatigue in the human motor system. Psychological Research 41, 345-354. Heuer, H., in press. ‘Selektive Ermtiding im Motorischen System’. In: W. Michaelis (ed.), Bericht iiber den 32. Kongress der DGfPs. Kerr, B., 1978. ‘Task factors that influence selection and preparation for voluntary movements’. In: G.E. Stelmach (ed.), Information processing in motor control and learning. New York: Academic Press.
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choice reaction time: I
41
Klapp, ST., 1977a. ‘Reaction time analysis of programmed control’. In: R. Hutton (ed.), Exercise and sport sciences reviews, vol. V. Santa Barbara, CA: Journal Publishing Affiliates. Klapp., S.T., 1977b. Response programming, as assessed by reaction time, does not establish commands for particular muscles. Journal of Motor Behavior 9, 301-312. Klapp, S.T., E.P. Wyatt and W.M. Lingo, 1974. Response programming in simple and choice reactions. Journal of Motor Behavior 6, 263-271. Klapp, S.T., J. Abbott, K. Coffman, D. Grein, R. Snider and F. Young, 1979. Simple and choice reaction time methods in the study of motor programming. Journal of Motor Behavior 11,91-101. Marteniuk, R.G. and C.L. MacKenzie, 1980. ‘Information processing in movement organization and execution’. In: R.S. Nickerson (ed.), Attention and performance VIII. Hi&dale, NJ: Erlbaum. Megaw, E.J., 1972. Direction and extent uncertainty in step-in-put tracking. Journal of Motor Behavior 4,171-186. Requin, J., 1980. ‘Towards a psychobiology of preparation for action’. In: G.E. Stelmach and J. Requin (eds.), Tutorials in motor behavior. Amsterdam: North-Holland. Rosenbaum, D.A., 1977. Selective adaptation of ‘command neurons’ in the human motor system. Neuropsychologia 15, 81-91. Rosenbaum, D.A., 1978. Selecting the side of the body, limb, and direction of forthcoming movements. Paper presented at the 19th Annual Meeting of the Psychonomic Society, San Antonio, TX. Rosenbaum, D.A., 1980. Human movement initiation: specification of arm, direction, and extent. Journal of Experimental Psychology: General 109,444-474. Rosenbaum, D.A. and M. Radford,,l977. Sensory feedback does not cause selective adaptation of human ‘command neurons’. Perceptual and Motor SkiIls 44,447-451. Schmidt, R.A., 1975. A schema theory of discrete motor skill learning. Psychological Review 82,225-260. Semjen, A., J. Requin and N. Fiori, 1978. The interactive effect of foreperiod duration and response-movement characteristics upon choice-reaction time in a pointing task. Journal of Human Movement Studies 4, 108-118. Sternberg, S., S. MonseIl, R.L. Knoll and C.W. Wright, 1978. “The latency and duration of rapid movement sequences: comparisons of speech and typewriting’. In: G.E. Stelmach (ed.), Information processing in motor control and learning. New York: Academic Press.
BINARY CHOICE REACTION MOTOR EQUIVALENCE * Herbert
35
TIME AS A CRITERION
OF
HEUER
University of Diisseldorf, W. Germany
Accepted April 1981
In a binary choice situation the two alternative movements may vary in the degree in which they are equivalent in respect to controlling processes and/or structures. With a higher degree of motor equivalence a shorter RT is to be expected. A series of five experiments shows that a movement of a finger of one hand has a shorter latency if the alternative movement with the other hand is of the same form than in case of different forms. There is no evidence of a corresponding effect of using the same or different fingers with both hands. These results indicate that programming of the form of a movement is at least partly independent of the muscles involved in movement execution.
Introduction Since the pioneering work of Henry and Rogers (1960) a number of experiments has demonstrated that RT depends on certain physical characteristics of the response (for reviews see Klapp 1977a; Kerr 1978; Marieniuk and MacKenzie 1980; Henry 1980), but only few experiments were devoted to the effects of the relationship between the physical characteristics of the alternative responses in a choice situation. These experiments bear on the problem of motor equivalence. The term “motor equivalence” is intended to refer to the similarity or overlap of the processes and/or structures involved in the control of different movements. It may be given a more specific meaning in the context of two different but not incompatible conceptualizations of motor control.
* Mailing address: Herbert Heuer, UniversitLt Diisseldorf, Psychologisches Institut, Universitltsstrasse 1, D-4000 Diisseldorf 1, W. Germany
000 1-69 1S/82/0000-0000/$02.75
0 1982 North-Holland
36
H. Heuer /Binary
choice reaction time: I
The concept of a motor program is now in widespread use. According to Schmidt (1975) a motor program controls a certain class of movements. Which movement of the class is executed depends on additional specifications or parameters. Therefore, different movements may differ in the program or in a certain number of parameters and will be correspondingly more or less equivalent. The second conceptualization was introduced by Rosenbaum (1977). The basic suggestion is that certain physical characteristics of a movement may be determined by the activity of a certain group of specific neurons. These hypothetical neural structures are analogous to the feature detectors of the visual system. Different movements may involve identical structures to a varying degree, and this structural overlap then defines the degree of motor equivalence in this context. The general expectation is that choice RT will be shorter if the response alternatives show a higher degree of motor equivalence. For example Megaw (1972) interpreted the shorter RTs in case of movement extent uncertainty than in case of direction uncertainty as indicating that the same motor program is involved in the control of movements which differ in amplitude, but different programs in the control of movements in different directions. In a similar way Rosenbaum (1978; 1980) demonstrated the relationship of choice RT to the number of identical parameters of the response alternatives. The expectation of a relationship between the degree of motor equivalence and choice RT implies certain assumptions about the preparation before the imperative signal. If subjects prepare what is common to the responses (“conjunctive preparation”) movements of higher equivalence will be prepared more than less equivalent movements and therefore the RT will be faster. The same is to be expected under the assumption of “single preparation” where subjects prepare only one of the response alternatives, but depending on the degree of motor equivalence the shift to the unprepared response will take more or less time (see Semjen et al. 1978; Requin 1980). In contrast, no relationship will exist if there is “multiple preparation” where subjects prepare both responses completely (Rosenbaum 1980). Up to now we have considered choice RT as being dependent on the degree of motor equivalence. This hypothesis of course cannot be verified because the degree of motor equivalence can only be varied via the relationship between the physical characteristics of the alternative responses, and there need not be any simple relation between physical
H. Heuer /Binary
choice reaction time: I
37
similarity and the similarity or overlap of the underlying control processes. Therefore, it is preferable to consider choice RT as a criterion of motor equivalence. This means to presuppose a relationship between choice RT and the degree of motor equivalence, but the validity of this supposition can be examined by a comparison of different criteria. At least three other criteria of motor equivalence have been suggested which were derived from one or the other of the two conceptualizations mentioned above. In general, they are based on after-effects which one movement has on the execution of another movement, larger after-effects being taken as indication of a higher degree of motor equivalence: (1) Contralateral effects of fast movements performed with one hand for a certain time on speed and variability of movements performed with the other hand afterwards (Rosenbaum 1977; Rosenbaum and Radford 1977; Heuer 1980, in press) (2) effects of different movements on the acceleration pattern of a following movement (Heuer 1979) (3) sequential effects in RT experiments (van Galen 1980) It is obviously desirable to explore the relations between the different techniques, which are all intended to give indications of the degree of motor equivalence but which will certainly each have its own peculiarities. The present experiments were designed as a first step in this direction. Heuer ( 1980, in press) used the “selective fatigue” technique introduced by Rosenbaum (1977) and Rosenbaum and Radford (1977) to test the differences in the degree of motor equivalence between pairs of movements which were varied in respect to form and muscles involved. Subjects had to perform tapping movements with the index finger of the right hand as fast as possible for a period of 30 sec. Just before this test period they performed one of four different movements with the left hand for 30 sec. These movements differed from the test movement with the right hand in respect to form and/or muscles involved. They were performed with the index finger or the thumb, and their form was tapping or alternating. While tapping is a simple up-and-down movement, alternating is mainly a horizontal movement with only a small vertical component. The results were a heightened variability of the movement times if
H. Heuer /Binary
38
choice reaction time: I
the foregoing movements were of identical form (form effect) or if homologous muscles were involved (muscle effect) relative to different forms or non-homologous muscles. This was taken as evidence for a reduced degree of motor equivalence if the form of the movements is different or the muscles involved are non-homologous. From these results one should expect a form effect and a muscle effect in a choice RT experiment using the same movements with shorter RTs in case of identical forms or homologous muscles.
The experiment Method Subjects
There were 50 female Ss in total, ranging ln age from 16 to 29 years. In each experiment 10 Ss participated. They were paid a fixed amount of money, independent of performance. Experiments
The five experiments differed in the movement with the right hand, which was the same for all conditions in one experiment and which will be referred to as criterion movement in the following. The different criterion movements are listed in table 1. They will be used to refer to the different experiments. Different criterion movements were used to make sure that any effects observed are due to the relation between the criterion movement and the alternative movement with the left hand and not just to the specific kind of movement used as alternative. As shown in table 1, alternating with the index finger was used twice as a criterion movement. In exp. AI/S alternating movements with the left hand were symmetrical to the alternating movements with the right hand, in exp. AI/D alter-
Table 1 Criterion movements in the five experiments. Exp.
Criterion movement
Abbreviation
I II III IV V
Tapping, Index finger Tapping, Thumb Alternating, Index finger Alternating, Index finger Alternating, Thumb
TI TT AI/S a) AI/D a) AT
a) Alternating movements with both hands were Symmetrical (AI/S) or in the same Direction (AI/D)
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nating movements the left. Experimental
with both hands were of the same direction,
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always starting to
conditions
Four conditions were run in each experiment. The conditions will be labelled either by the specific alternative movement involved or by the relation of the alternative to the criterion movement: F=/M= (form equal/muscles homologous), F=/Mf (form equal/muscles non-homologous), F#/M= (form different/muscles homologous) and Ff/Mf (form different/muscles non-homologous). Apparatus
The movements were performed with the same apparatus that was used by Heuer (1980, in press) in the selective fatigue experiments. The Ss grasped horizontally mounted handles with each hand, which were about 40 cm laterally apart and about 4 cm above table top. The height was adjusted so that the Ss could comfortably reach a black button with their stretched index finger or another black button with their laterally stretched thumb. In the case of tapping a steel wire was attached by means of adhesive tape near the base of the finger nail. This steel wire rotated around its pivot when the S lifted her finger and activated a switch as soon as the finger reached a height of approximately 5 cm. As soon as the S lifted her finger, again when she reached the defined height, and a third time when she depressed the black button, she heard a tone of 30 msec duration. In 2.5 cm distance in the direction towards the median plane of the S there was another button of orange colour (for the thumb this orange button was only slightly displaced towards the median plane but more towards the S). In performing alternating movements, the Ss had to lift their finger from the black button, depress the orange one and again the black one. At each occasion they heard the short tone. For exp. AI/D and AT the orange and black button were interchanged for the left hand. Thus, the orange button was always to the left of the black one. Between the two buttons there was a small barrier which forced the movements to reach a minimum height of approximately 0.5 cm. ‘In front of the Ss, at a distance of about 10 cm from the buttons, there were three stimulus lights. A green one of 5 mm diameter in the middle served as a warning signal. The imperative signals were two red light-emitting diodes of 2 mm diameter at a distance of 2 cm to the left and to the right of the warning signal. The whole experiment was controlled by a microcomputer. Design and procedure
Each S took part in six sessions on consecutive days (with a few exceptions). A session comprised four blocks of trials with breaks of 5- 10 mm between blocks, each block with a certain movement combination according to the different conditions. Over the last four sessions the conditions were arranged in a latin square for each S. The first two sessions were for training. They were identical with the last two sessions. Each block consisted of 110 trials, the first 10 again for training. Of the last 100 trials, 50 called for a response with the left hand and 50 for a response with the right one in a random order.
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H. Heuer /Binary choice reaction time: I
A trial was initiated by S when she shortly lifted one of her fingers and pressed the black button again. After a period of 1 set the warning signal .was presented, which remained on for 2 sec. If the S started a movement during this period, or more exactly, if she lifted one of the two fingers from the black button, the trial was interrupted and had to be initiated again. With the end of the foreperiod the imperative signal was presented and remained on until the end of the correct movement. Two kinds of errors were recorded. In case of a choice error the S lifted the wrong finger from the black button, in case of an execution error either a tapping movement did not reach the required height or the orange button was not depressed with an alternating movement. All trials in which an error occurred were repeated at the end of each block. At the beginning of the first session the Ss were made familiar with the movements required. The instruction demanded for fast and correct movements. Dependent variables For each trial the reaction time and the movement time were measured. The reaction time interval lasted from the presentation of the imperative signal until the S lifted her finger from the correct black button. The movement time interval started with the end of the reaction time interval and was finished when S depressed the black button again. For each S and each alternative in each condition there were 200 measurements in total. The analysis is based on the mean and the standard deviation of these measurements. Reaction times outside the range from 1.50 to 1000 msec and movement times larger than 1500 msec were neglected. Results R T for the criterion movements The mean RTs and the mean standard deviations for all five experiments are presented in fig. 1 as a function of the specific alternative movement. In all five experiments the RT is smaller when the alternative movement is of the same form as the criterion movement. In the two experiments with tapping as criterion movement it is smaller with tapping as alternative, in the experiments using alternating as criterion movement with alternating. The data were analysed by mean of a fixed-effects ANOVA (BMDP2V). The effect of the form relation is significant in all experiments except exp. TT (TI: F( 1,9) = 39.74, p < 0.01; TT: F( 1,9) = 3.94, p < 0.10; AI/S: F(1,9) = 5.12, p < 0.05; AI/D: F(1,9) = 8.61, p < 0.05; AT: F(1,9) = 23.72, p < 0.01). The mean standard deviations show the same pattern, but it is not as distinct as with the mean RTs. The effect of the form relation is present in all experiments, but significant only in three of them (TI: F( 1,9) = 17.67, p < 0.01; AI/D: F( 1,9) = 11.12,p<0.05;AT:F(1,9)=7.43,p<0.05). In contrast to the consistent effects of the form relation the muscle relation shows a significant effect only in exp. AI/S (F( 1,9) = 12.63, p < 0.01). Here the reaction time is shorter when both movements are performed with the same finger of each hand. In the other four experiments the effect is not significant and in exp. TT it is even in the wrong direction.
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Fig. 1. Mean RTs and mean standard deviations for the criterion movements (right hand).
The effect of the muscle relation on the standard deviations is in none of the five experiments significant. Its direction is always the same as the effect on the mean RTs. The interaction of form and muscle relation is never significant. R T for the alternative
movements
The criterion movements are identical for all four conditions of each experiment, and the differences between conditions can be unequivocally attributed to the different alternative movements. The RTs for the alternative movements should again depend on the relation to the criterion movements, but a second factor is of importance, because the alternative movements differ across conditions. The RTs will
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Fig. 2. Mean RTs for the alternative movements (left hand).
therefore show the combined effects of the latencies with the different movements in isolation, which might reflect differences in programming times, and the relation between the response alternatives. The mean RTs are presented in fig. 2. The most obvious fact from fig. 2 is that the differences between different alternative movements reflect mainly the differences in the relation to the criterion movement. In the first two experiments the RTs are significantly shorter with tapping than with alternating (TI: F( 1,9) = 10.76, p < 0.01; TT: F( 1,9) = 46.94, p < O.Ol), but in the other three experiments they are slightly shorter with alternating although these differences are not significant. Similar effects are to be found with the mean standard deviations. In the first two experiments they are smaller with tapping (TI: F(1,9) = 3.99, p < 0.10; TT: F(1,9) = 8.49, p < 0.05), and in the other experiments there are no significant effects of the form relation. The effect of the muscles involved is significant in all experiments except exp. TT. The RT is shorter with movements of the thumb than with movements of the index finger in exp. TI (F( 1,9) = 23.18, p < 0.01) and AI/S (F( 1,9) = 6.86, p < 0.05), but longer in exp. AI/D (F( 1,9> = 8.99, p < 0.05) and AT (F( 1,9) = 28.21, p < 0.05). These effects show no consistent relation either to the specific finger used for the alternative movement nor to its relation to the finger used for the criterion movement: in exp. TI, AI/S and AT the mean RT is significantly shorter when different fingers are used, but in exp. AI/D it is shorter with identical fingers of both hands. With the standard deviation there is a significant effect of the muscle relation only in exp. AT (F( 1,9) = 5.58, p < 0.05), which parallels the effect found for the mean RT. This parallelity does not hold for all of the other experiments. A significant interaction between form and muscle relation again does not show up in any of the experiments.
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Fig. 3. Mean MTs for the criterion movements (right hand).
MT for criterion
movements
The mean movement times are presented in fig. 3. The MT is always longer with alternating as the alternative movement. This effect, which is obviously due to the specific alternative but not to the relation between the two movements, is significant in allexperiments except exp. AI/D (TI: F(1,9)= 7.41, p < O.OS;TT: F(1,9) = 8.68,p<0.05,AI/S:F(1,9)=17.01,p
errors
The number of choice errors was determined for each S and each condition. In a first analysis erroneous responses to both signals were collapsed and the existence of an effect of the form relation or the muscle relation was tested by means of a simple binomial sign test (Dixon and Mood 1946). In none of the five experiments there was a significant muscle effect, and only in exp. AI/D the form effect was significant: 8 out of 10 Ss showed more errors with response alternatives of equal form and only one S with alternatives of different form (means: 3.60 vs 2.55). In the other experiments the differences were negligible, ranging from 0 to 0.35, but never being of negative sign. In a second analysis the differences in the number of errors to both signals were
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choice reaction time: I
taken into consideration. This was done as a test for biases in favour of one or the other of the response alternatives which might be different in different conditions. According to results by Fitts et al. (1963) this kind of bias would be indicated by a shorter RT and a smaller number of errors in response to the favoured signal. Again, there was no muscle effect, but the form effect was significant in three experiments. In these experiments (TI, AI/D, AT) there was a bias towards less errors in response to the right signal in conditions with response alternatives of identical form, and with alternatives of different form there were fewer errors in response to the left signal. In the two other experiments (TT and AI/S) this pattern was not observed, but there were always less errors in response to the right signal, and in the conditions with alternatives of different form this tendency was even stronger than in equal form conditions, although not significantly so. Execution
errors
Execution errors were analysed only for the criterion movements with the right hand. In case of alternating they were very rare events (less then 0.2%), but in case of tapping their frequency was higher. In both of the two experiments with tapping as the criterion movement (TI and TT) they were significantly more frequent when the alternative movement was of the same form (sign test), and in exp. TT they were more frequent with response alternatives involving non-homologous muscles than in case of homologous ones, while in exp. TI the muscle effect was non-significant.
Discussion In all five experiments there is a consistent effect of the form of the alternative movement: the binary choice RT with a certain movement is smaller when the alternative movement with the other hand is of the same form than with an alternative of a different form. This effect can be unequivocally attributed to the form relation. The difference in the mean RT is paralleled by a difference in the mean variability of the RTs. Contrary to expectation there is no consistent effect of the muscle relation. This kind of effect appeared only in one experiment and is probably a chance result. These results on RT show no consistent relation to the pattern of results obtained with the movement times. While reaction times depend on the relation between the response alternatives, movement times depend on the specific alternative. Thus, the RT effects cannot be considered as being secondary to MT effects. We are inclined to reject any interpretation of the observed form effect as being an artefact due to speed-accuracy tradeoff, although in
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case of significant differences execution or choice errors are of higher frequency in conditions with response alternatives of identical form. There are two reasons for our rejection. Firstly, a significant form effect in respect to execution errors was observed in only two experiments, but in the three other experiments a significant RT effect was observed without a corresponding effect in the number of execution errors. A similar argument holds for the form effect in respect to choice errors. The second reason pertains to choice errors only. An inverse relation between RT and error frequency is not necessarily due to different accuracy criteria which Ss adopt for one or the other reason. It could as well be explained by differences in the degree of motor equivalence which make confusions more or less likely. There is another effect observed with the number of choice errors which could be taken as a basis for an interpretation of the RT results. According to differences in the error frequencies in response to the two signals subjects favour the right one in equal form conditions but the left one in conditions with unequal form in three of the experiments, This could explain the form effect observed with the RTs to the right signal which was the signal’demanding for the criterion movement. But if this interpretation were valid the RTs with the left hand should differ in the opposite direction, being larger in equal form conditions and smaller if the response alternatives are of different form. Since the latencies of the alternative movements show the same effect as the latencies of the criterion movements this interpretation can be rejected. In our opinion there is good reason to take the effect of the form relation on RT as an indicator of a higher degree of motor equivalence of movements of identical form, which are performed with different hands or even with different fingers of different hands. Thus, programming of the form of a movement is not inherently linked to the use of certain muscles. This is a corrobation of Klapp’s (1977b) conclusion which was based on a different experimental procedure. Contrary to expectation there was no muscle effect. This is obviously not in line with the results obtained with another criterion of motor equivalence, namely the contralateral transfer technique (Heuer 1980, in press). At present only one conclusion can be drawn from this inconsistency: there are factors specific to the different techniques which may under certain conditions result in “false positive” or “false negative” results. Although the main concern of this series of experiments is the effect
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choice reaction time: I
of different alternative movements with the left hand on the latencies of identical criterion movements with the right hand, the left hand RTs deserve some comment. These results bear on the problem of whether choice RTs or simple RTs are to be preferred for the study of motor programming times (see Klapp 1977a; Klapp et al. 1974; Klapp et al. 1979; Sternberg et al. 1978). Assume that the programming time for tapping is somewhat smaller than that for alternating. In a choice situation this difference will in most cases be contaminated by differences which are due to the relation between the movements under study. In the first two experiments of our series with tapping as the criterion movement the basic difference was enhanced. In these experiments the RT for tapping was significantly shorter than that for alternating. Contrary to this the RT difference between tapping and alternating was reversed in the three experiments with alternating as the criterion movement, although not significantly so. Here the form relation favours alternating. It might be hard to obtain RT measurements with different movements in a choice situation which are not contaminated by effects of the relationship between the two response alternatives.
References Dixon, W.J. and A.M. Mood, 1946. The statistical sign test. Journal of the American Statistical Association 41, 557-566. Fitts, P.M., J.R. Peterson and G. Wolpe, 1963. Cognitive aspects of information processing: 11. Adjustments to stimulus redundacy. Journal of Experimental Psychology 65,423-432. GaIen, G.P. van, 1980. ‘Handwriting and drawing: a two-stage model of complex motor behavior’. In: G.E. Stelmach and J. Requin (eds.), Tutorials in motor behavior. Amsterdam: North-Holland. Henry, F.M., 1980. Use of simple reaction time in motor programming studies: a reply to KIapp, Wyatt and Lingo. Journal of Motor Behavior 12, 163-168. Henry, F.M. and D.E. Rogers, 1960. Increased response latency for complicated movements and a ‘memory-drum’ theory of neuromotor reaction. Research Quarterly 31,448-458. Heuer, H., 1979. Uber Bewegungsprogramme bei willkiirlichen Bewegungen. Berichte aus den Fachbereich Psychologie der Phillipps-Universitat, Marburg/Lahn, Nr. 76. Heuer, H., 1980. Selective fatigue in the human motor system. Psychological Research 41, 345-354. Heuer, H., in press. ‘Selektive Ermtiding im Motorischen System’. In: W. Michaelis (ed.), Bericht iiber den 32. Kongress der DGfPs. Kerr, B., 1978. ‘Task factors that influence selection and preparation for voluntary movements’. In: G.E. Stelmach (ed.), Information processing in motor control and learning. New York: Academic Press.
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Klapp, ST., 1977a. ‘Reaction time analysis of programmed control’. In: R. Hutton (ed.), Exercise and sport sciences reviews, vol. V. Santa Barbara, CA: Journal Publishing Affiliates. Klapp., S.T., 1977b. Response programming, as assessed by reaction time, does not establish commands for particular muscles. Journal of Motor Behavior 9, 301-312. Klapp, S.T., E.P. Wyatt and W.M. Lingo, 1974. Response programming in simple and choice reactions. Journal of Motor Behavior 6, 263-271. Klapp, S.T., J. Abbott, K. Coffman, D. Grein, R. Snider and F. Young, 1979. Simple and choice reaction time methods in the study of motor programming. Journal of Motor Behavior 11,91-101. Marteniuk, R.G. and C.L. MacKenzie, 1980. ‘Information processing in movement organization and execution’. In: R.S. Nickerson (ed.), Attention and performance VIII. Hi&dale, NJ: Erlbaum. Megaw, E.J., 1972. Direction and extent uncertainty in step-in-put tracking. Journal of Motor Behavior 4,171-186. Requin, J., 1980. ‘Towards a psychobiology of preparation for action’. In: G.E. Stelmach and J. Requin (eds.), Tutorials in motor behavior. Amsterdam: North-Holland. Rosenbaum, D.A., 1977. Selective adaptation of ‘command neurons’ in the human motor system. Neuropsychologia 15, 81-91. Rosenbaum, D.A., 1978. Selecting the side of the body, limb, and direction of forthcoming movements. Paper presented at the 19th Annual Meeting of the Psychonomic Society, San Antonio, TX. Rosenbaum, D.A., 1980. Human movement initiation: specification of arm, direction, and extent. Journal of Experimental Psychology: General 109,444-474. Rosenbaum, D.A. and M. Radford,,l977. Sensory feedback does not cause selective adaptation of human ‘command neurons’. Perceptual and Motor SkiIls 44,447-451. Schmidt, R.A., 1975. A schema theory of discrete motor skill learning. Psychological Review 82,225-260. Semjen, A., J. Requin and N. Fiori, 1978. The interactive effect of foreperiod duration and response-movement characteristics upon choice-reaction time in a pointing task. Journal of Human Movement Studies 4, 108-118. Sternberg, S., S. MonseIl, R.L. Knoll and C.W. Wright, 1978. “The latency and duration of rapid movement sequences: comparisons of speech and typewriting’. In: G.E. Stelmach (ed.), Information processing in motor control and learning. New York: Academic Press.