Stimulus and response contributions to the children's reaction-time repetition effect

Adults and 8-, 10-, 12-, and 14-year olds completed a serial reaction-time task with two stimuli mapped to each of two responses and 100-, 500-, and 1000-msec response-stimulus intervals (RSIs). Trials were classified as (1) identical (same stimulus and same response on two consecutive trials), (2) response equivalent (different stimulus but same response on two consecutive trials), or (3) different (different stimulus and different response on two consecutive trials). Identical and different trials were compared as a general indication of repetition effects. Response-equivalent minus identical reaction time identified stimulus contributions, and different minus response-equivalent reaction time identified response contributions. Adults received a repetition advantage at all RSIs and children received a repetition advantage at 500- and 1000- but not 100-msec RSIs. Stimulus contributions accounted for the repetition effect for both adults and children. At the 500- and 1000-msec RSIs, both the overall repetition effect and stimulus contribution were positive and decreased in magnitude as age increased. The response contribution was independent of RSI and was negative for 8- and 10-year-olds and near zero or positive for older performers. At the longer RSIs, positive stimulus contributions were sufficient to overcome the negative response contributions present for younger children.     

Common features of the “repetition” and “same-different” effects in reaction time experiments

Using comparable stimulus and response sets, and the same Ss, the “repetition” and “same-different” effects were studied in two experiments involving several reaction-time (RT) tasks. In Experiment 1, these effects were examined at a 2-sec interval between successive stimuli in the simple (SRT), the recognition (RRT), the choice (CRT), the same-different recognition(S-DRRT),and the same-different choice (S-DCRT) tasks. In Experiment 2, the effects were studied at a 1 O-sec interval in the CRT and S-DCRT tasks. The results suggest the following mainconclusions: (1)The positive repetition effect (i.e., shorter reaction times on “repeated” trials than on “nonrepeated” trials) is not only a feature of the CRT task but may also occur in the SRT and RRT tasks. (2) With increasing intertrial interval, the magnitude of the positive repetition effect diminishes and then reverses into a negative repetition effect. (3) The positive same-different effect (ie., shorter reaction times on “same” trials than on “different” trials) is affected by an increase in interstimulus interval ina manner that parallels the effect of intertrial interval on the positive repetition effect, suggesting that the processes underlying the two effects are mainly the same. (4) These changes in the magnitude and direction of the repetition and same-different effects are probably a function of discrimination difficulty.     

Probing the motor program: Effects of output competition during movement preparation

A probe reaction-time paradigm was used to investigate the capacity demands of planning rapid aiming movements. Subjects were required to respond either vocally or manually to an auditory probe presented during the reaction-time interval preceding a pointing response. When a vocal response was required probe reaction time increased systematically with the complexity of the pointing movements. Presumably this is because a more complex task requires more programming resources. When a manual response was required, reaction-time data for both the pointing task and the probe indicate that the structural constraints inherent in programming two similar movements may force subjects to engage in common response preparation. The methodological and theoretical implications of these findings are discussed.     

Parametric coupling and generalized decoupling revealed by concurrent and successive isometric contractions of distal muscles

In two experiments we examined the hypothesis of transient parametric coupling during the specification of peak forces of isometric contractions produced by the left and right hand. In the first experiment participants had to produce bimanual contractions with same and different target forces as rapidly as possible in response to an auditory signal; target forces were cued visually with variable cueing intervals. At short cueing intervals reaction times were longer when different peak forces had to be specified than when same peak forces were cued, and this reaction-time difference declined as the cueing interval was increased. Independent of the cueing interval intermanual correlations of peak forces, rise times, and reaction times were smaller in conditions with different peak forces than in those with same peak forces. In the second experiment imperative signals for left-hand and right-hand contractions were separated in time. Target forces for the first response were cued with variable cueing intervals, while for the second response the cues were presented simultaneously with the second imperative signal. Reaction time of the second response was longer when target forces for the two successive responses were different rather than same, and this reaction-time difference declined when the delay of the second signal was increased as well as when the cueing interval for the first response became longer. These results are consistent with the hypothesis of a transient cross-talk between concurrent processes of peak-force specifications; in addition they indicate generalization of the decoupling required to specify different peak forces concurrently to the specification of temporal response characteristics and to processes of response initiation.     

After-effects of responding and of withholding responses in C.RT tasks

The effects of response repetition on choice RT were compared in b-reaction and in c-reaction tasks [Experiments I(a) and I(b)]. The difference in RTs for repeated and for non-repeated responses was found to be less for c-reaction than for b-reaction tasks. This seemed to be because in c-reaction tasks subjects can prepare themselves to make the same response on every trial, so that there is little further RT reduction consequent on immediate response repetition. In b-reaction tasks subjects cannot always prepare to make the same response, so that the difference between response repetition RT and responce alteration RT is greater. Experiment II examined transitions between events in a serial, self-paced C.RT task in which subjects made a different response to each of two signals but withheld any response to the onset of a third. In this task responses were faster when they followed other, different responses than when they followed “no go” trials. The results of these experiments allow us to reject, even for very elementary tasks, a simple “S--R connection network” model for the processes involved in the identification of signals and the production of responses to them.     

Reaction times for fine discrete movements

Three experiments (ns = 20, 10, and 20) were conducted in which the reaction times for responses to complexity were investigated for small-scale, discrete, terminated movements. In a choice reaction-time situation, the reaction time for the finger-lift response was longer than that for the finger-lift response followed by the pressing of another key with the same finger. The reaction times for these responses, however, did not differ in a simple reaction-time situation. The difference in reaction times between these responses may have been associated with some differences in allocation of the subjects' internal resources. The subjects' attention might be more attracted to the more complex response.     

Influence of practice on response-selection and response-implementation processes involved in the response-interference effect

In a choice reaction-time task, the response-interference effect is an increase in reaction times when the two possible responses are from the same hand compared to when the two possible responses are from different hands [Psychonomic Science 2 (1965) 55-56; Human Motor Control, Academic Press, San Diego, CA, 1991]. Although the influence of practice on other reaction-time effects (i.e., the complexity effect and precuing) has been examined, research evaluating the influence of practice on the response-interference effect is limited. Therefore, two experiments were conducted to determine the influence of practice on the response-interference effect. In Experiment 1, a bilateral transfer task was used to assess the influence of practice on the response-selection processes associated with the response-interference effect. The practice results indicated decreased reaction times, but did not influence the response-interference effect. In Experiment 2, a priming task was used to assess the influence of practice on response-implementation processes associated with the response-interference effect. The reaction time results indicated a change in the response-interference effect. The results of these two experiments suggest that with only two fingers on response keys, practice alters the mechanical constraints affecting the response-implementation processes and thereby decreases the response-interference effect.     

Evidence for abstract response codes: Ear-hand correspondence effects in a three-choice reaction-time task

A three-choice reaction-time task was used to investigate the source-of-stimulation effect, that is, the tendency for subjects to react faster and more accurately to a stimulus if the spatial locations of the stimulus and the response correspond than if they do not. Auditory stimuli varied on dimensions of tonal frequency and spatial location, although only the former was relevant for response selection. Responses were found to be faster for the conditions in which stimulus location and response location corresponded than for those in which they did not, but stimulus location had no effect on differences between the two hands with bimanual responses. These results support the hypothesis that the source-of-stimulation effect is due to response plans which interact at a level prior to the programming of the motor response.     

Programmed control of aimed movements revisited the role of target visibility and symmetry

Reaction time prior to starting a 2-mm amplitude aimed movement was studied as a function to target size and experimental procedure. Consistent with a report by Klapp, choice reaction time increased as target size decreased when the visual signal that initiated the reaction time interval also indicated which of two targets was to be hit. This result implies response programming during the reaction time interval, with more programming time for slower movements to smaller targets. By contrast, in a simple reaction time procedure, there was no effect of target size on reaction time, suggesting that the response can be programmed in advance when the appropriate target is precued. This provided a control for speed-accuracy trade-off, supporting the programming interpretation of the choice reaction time result. In another condition in which both targets could be viewed while waiting for the auditory signal that initiated the reaction time interval and indicated which target to hit, choice reaction time was independent of target size provided that both possible targets on each trial were of the same size. The overall results suggest that response programs include both spatial and temporal information, and that parallel programming of different spatial goals is possible provided that the responses are of the same duration.     

Equivalency of reaction times for simple and primed tasks

Both simple and choice reaction-time tasks have been used to examine the processes involved in response preparation. With a response priming task, complete information prior to the presentation of the imperative stimulus is given as to which response among several will be required. It is assumed that with the priming procedure, the advanced information allows for the complete preparation of the response to be made prior to the presentation of the imperative stimulus [Klapp, S. T. (1996). Reaction time analysis of central motor control. In H. N. Zelaznik (Ed.), Advances in motor learning and control (pp. 13-36). Champaign, IL: Human Kinetics]. This study used two experiments to test the underlying assumption that the processes occurring within the reaction time interval are equivalent for simple and primed tasks, and to determine if the validity of the prime influences performance. In both experiments, participants completed three reaction-time tasks: simple, primed (100%), and choice. The second experiment added a fourth task in which the prime was valid only 80% of the time. In both experiments, the reaction times were significantly slower for the choice task than for either the simple or 100%-primed tasks. Most important, the simple and primed (100%) reaction times were not significantly different. For the second experiment, the reaction times were not significantly different for the choice and 80%-valid prime tasks. The results of these experiments demonstrate that equivalent response preparation processes occur for simple and primed tasks, but that the validity of the prime does influence the response preparation processes for the primed task. Thus, equivalency is not achieved when invalid primes are used.     

Does Immediate Arousal Enhance Response Force in Simple Reaction Time?

Three experiments assessed the hypothesis that immediate arousal enhances response force in speeded reaction-time tasks. Immediate arousal was manipulated via the physical characteristics of a warning signal that closely preceded the imperative response signal. The first experiment revealed that responses were more forceful and faster for a loud than for a soft warning signal. The second experiment manipulated the duration of an auditory warning signal; more forceful but slower responses were obtained for longer durations of the warning signal. The third experiment employed a visual warning signal, and its intensity was either rather weak or moderately bright; more forceful responses and slightly faster responses were observed for the brighter warning signal. Although the results of Experiment 1 and 2 may agree with an arousal account, the findings of Experiment 3 argue against such an account. A stimulus-response compatibility hypothesis is suggested as one possible alternative account.     

Sequential effects in auditory choice reaction time tasks

This paper concerns sequential effects in choice reaction time tasks. Performance in two interleaved auditory tasks was examined, and two general types of sequential effects were revealed. First, a response repetition effect occurred: Subjects were facilitated in responding when both the stimulus and the response were immediately repeated. Generally, it appeared that subjects were operating according to the bypass rule—that is, repeat the response if the stimulus or some aspect thereof is repeated from the preceding trial; otherwise, change the response. In addition, the experiment also revealed a second type of sequential effect, known as a task-switching effect. Subjects were overall slower to respond when the task changed between adjacent trials than when there was no task change. A final result was that subjects were markedly impaired when the stimulus changed but the same response had to be repeated. This finding has been reported elsewhere when purely visual tasks have been used. Hence, it seems that particular difficulties arise, in such sequential testing situations, when type-distinct stimuli are grouped into the same response categories.     

Response Selection Contributes to the Preparation Cost for Bimanual Asymmetric Movements

Movement preparation of bimanual asymmetric movements takes more time than bimanual symmetric movements in choice reaction-time conditions. This bimanual asymmetric cost may be caused by increased processing demands on any stage of movement preparation. The authors tested the contributions of each stage of movement preparation to the asymmetric cost by using the additive factors method. This involved altering the stimulus contrast, response compatibility, and response complexity. These manipulations changed the processing demands on stimulus identification, response selection, and response programming, respectively. Any manipulation with a larger reaction time cost than control suggests that stage contributes to the bimanual asymmetric cost. The bimanual asymmetric cost was larger for incompatible stimuli, which supports that response selection contributes to the bimanual asymmetric cost.     

The influence of response grouping on free-choice decision making in a response selection task

Previous research has demonstrated an advantage for the preparation of fingers on one hand over the preparation of fingers on two hands, and for the preparation of homologous fingers over that of non-homologous fingers. In the present study, we extended the precuing effects observed with finger responses to response selection under free-choice conditions. Participants were required to choose from a range of possible responses following the presentation of a precue that indicated which response to prepare (go-to precue) or prevent (no-go-to precue). In Experiment 1 the choice was between homologous and non-homologous finger responses on the hand opposite to the precue while in Experiment 2 the choice was between finger responses on the same or different hand to the precue. In the go-to precue condition, the frequency of homologous finger choices was more frequent than non-homologous finger responses. Similarly, participants chose finger responses on the same hand as the precue regardless of whether they were instructed to prepare or prevent the precued response. The hand effect bias was stronger than the finger effect bias. These findings are consistent with the Grouping Model (Adam, Hommel, & Umilta, 2003).     

Divided attention: Evidence for coactivation with redundant signals

Many models of divided attention assume that signals presented on different channels produce separate activations, any one of which can initiate a response. According to these models, detection responses are especially fast when signals are presented on two channels at the same time because the system can detect a signal in either of two ways. Such models predict a testable relation among reaction time distributions for conditions in which a single signal is presented as compared with a condition in which two signals are presented, and this prediction is tested in two tasks. A bimodal detection task required a simple speeded response to either a visual or an auditory signal. A letter search task required a choice response depending on whether or not a two-letter display included the signal letter “A.” Data from both tasks are inconsistent with the prediction. When two signals are presented, responses are faster than separate-activation models can explain. The results favor “coactivation” models, in which signals presented on different channels contribute to a common pool of activation that initiates a response.     

Perceived control

Permitting subjects to choose materials to be learned on a task enhances performance on that task. These results support the idea that choice increases the learner's perception of control, thereby enhancing motivation and performance. The purpose of the present experiments was to determine whether choosing responses to be learned on a paired-associate task would also benefit performance on a reaction-time task. Half of the subjects selected their responses to be learned on a paired-associate task while the remaining subjects were assigned responses. In one experiment, subjects then performed both the PA and RT tasks simultaneously, while in the second experiment the RT task was performed following the choice/force procedure. Providing the learner with the opportunity to choose produced a generalized increase in motivation, which resulted in significantly faster responding on the nonchosen RT task. Also discussed are the limitations of the effects of perceived control.     

On choosing between movement sequences: comments on Rose (1988)

One method of investigating human motor programming is to determine how the choice reaction time for a memorized response sequence depends on the composition of that sequence as well as the other sequence that may be required. Using this method, Rose (1988) found that the total number of responses in the two possible response sequences predicts the choice reaction time to initiate either one. On the basis of this result, Rose claimed that the hierarchical editor (HED) model of motor programming, developed by Rosenbaum, Inhoff, and Gordon (1984), may have to be reevaluated. In this commentary I argue that Rose's results are inconsistent with a precursor of the HED model, not with the HED model itself, that the HED model actually provides a better fit to Rose's data than her total-number-of-responses model, that in general, choice reaction time does not increase with the total number of possible responses, and that structural relations between alternative movement sequences are the main determinants of choice reaction time. Taken as a whole, the results suggest that possible responses are not held in completely readied form before being selected for execution. A further implication is that the storage capacity of the motor output buffer (the MOB) is extremely limited.     

Stimulus-Response Compatibility and Motor-Programming Effects: A Test of Theoretical Accounts of Compatibility

Traditional mental coding accounts of stimulus-response (S-R) compatibility suggest that the S-R translation stage is the locus for the effect (Umilta & Nicoletti, 1990; Wallace, 1971). However, recent response-priming accounts have suggested that the S-R translation and response-programming stages may interact to produce S-R compatibility effects (Kornblum, Hasbroucq, & Osman, 1990; Wickens. 1984; Zelaznik & Franz, 1990). Our study investigated the nature of the relation between these two stages relative to the S-R compat- ibility effect. Subjects performed a choice reaction-time task in response to visual stimuli. The critical manipulations in the study were of compatibility and response programming. The analysis revealed a significant compatibility effect but no interaction between the factors affecting compatibility and those affect- ing response programming. The results were consistent with the notion that the S-R translation stage of information processing is the locus of S-R compatibility effects. Thus S-R compatibility is an effect of the mental operations that occur within the S-R translation stage of human information processing.     

Failure to produce response variability with reinforcement

Two experiments attempted to train pigeons to produce variable response sequences. In the first, naive pigeons were exposed to a procedure requiring four pecks on each of two keys in any order, with a reinforcer delivered only if a given sequence was different from the preceding one. In the second experiment, the same pigeons were exposed to this procedure after having been trained successfully to alternate between two specific response sequences. In neither case did any pigeon produce more than a few different sequences or obtain more than 50% of the possible reinforcers. Stereotyped sequences developed even though stereotypy was not reinforced. It is suggested that reinforcers have both hedonic and informative properties and that the hedonic properties are responsible for sterotyped repetition of reinforced responses, even when stereotypy is negatively related to reinforcer delivery.     

Generalizations and extensions of the precue-utilization effect in rapid reactions.

The method of brief PSIs (precue-to-stimulus intervals) was used in three RT (reaction-time) experiments to explore the generality of the precue-utilization effect in rapid reactions, and to examine two extensions. This effect, which shows the self-contained performance in the choice reaction of the processing operations that culminate in response selection, generalized to a quantitative discrimination and to unequal stimulus-response (SR) frequencies. In the first extension, the reduction in wrong-alternative errors at relatively long PSIs indicated that these errors occur in conjunction with commitment to response actualization. In the second extension, the duration of discrimination-selection was found to be no longer for the less frequent of two SR alternatives. Taken together, these findings indicate that the effect of relative SR frequency, on incidence of errors as well as length of RT, fell on response-actualization processing. This is in accord with a number of previous findings and consonant with effects of RT variables on movement parameters but contrary to cumulative speed-accuracy models.