Subjective expectancy and choice reaction times

Previous findings suggested that selective response times might be affected both by the inter-stimulus interval and by the probability of occurrence of the stimulus for reaction. These two factors have been tested independently and have been found to influence reaction times in a fashion that an expectancy hypothesis would predict.     

Visual and auditory choice reaction times

Choice reaction times are measured for three values of a priori signal probability with three well-practiced observers. Two sets of data are taken with the only difference being the modality of the reaction signal. In one set of conditions it is auditory, in the other, visual. The auditory reaction times are faster than the visual and in addition several other differences are noted. The latency of the errors and correct responses are nearly equal for the auditory data. Error latencies are nearly 30% faster for the visual data. Non-stationary effects, autocorrelation between successive latencies and non-homogeneous distribution of errors, are clearly evident in the visual data, but are small or non-existent in the auditory data. The data are compared with several models of the choice reaction time process but none of the models is completely adequate.     

On the reduction of choice reaction times with practice

Information theory concepts have been discussed in relation to data from choice reaction time experiments. Specifically, it has been stated that choice reaction time is proportional to the logarithm of the number of randomly appearing alternative stimuli. It is suggested that the reported increase in choice reaction times with an increased number of alternatives is the result of insufficient practice. Data are provided to show that, with sufficient practice, this increase does not occur between two and four choices.     

The choice reaction times of single and dual jointed actions

The choice reaction times of dual (elbow and wrist) and single (elbow) jointed movements were measured using ‘mixed’ (dual and single) and ‘matched’ (both dual or both single) response pairings. Although subjects found it more difficult to execute dual jointed actions (as shown by error rate), there was no concomitant prolongation of latencies for acceptable responses. In the light of these findings, the utility of CRT as an index of motor programming complexity, and the claim that pre-programming of responses is precluded with CRT testing, were discussed.     

A biased random walk model for two choice reaction times

This paper generalizes Stone's (1960, Psychometrika 25, 251–260) random walk model of two choice response times (RTs) that is based on the sequential probability ratio test (SPRT) and that predicts equal correct and incorrect RTs to the same response. The generalized version allows a bias of the type found in signal detection theory to enter directly into the accumulation process so that ambivalent evidence may be seen as slightly favoring one alternative. The resulting biased SPRT model can predict any relation between correct and incorrect mean RTs. In particular, unlike the special symmetric case of Link and Heath's (1975, Psychometrika 40, 77–105) relative judgment theory (RJT), the biased SPRT model can predict that correct mean RTs are faster for one response but slower for the other. The biased SPRT model, the classical SPRT model, and the symmetric RJT model are all fit to the data of an RT deadline experiment reported by Green and Luce (1973, Attention and performance, New York: Academic Press) and it is shown that, of the three, the biased SPRT model provides the best account. Finally, a method for incorporating the same sort of bias into RJT models is sketched out.     

Effects of cocaine on simple reaction times and sensory thresholds in baboons.

The effects of chronic, daily administration of cocaine on auditory and visual reaction times and thresholds were studied in baboons. Single intramuscular injections of cocaine hydrochloride (0.1 to 5.6 mg/kg) were given once daily for periods of 10 to 25 days, and were followed immediately by psychophysical tests designed to assess cocaine's effects on simple reaction times as on auditory and visual threshold functions. Consistent reductions in reaction times were frequently observed over the cocaine dose range of 0.32 to 1.0 mg/kg; at higher doses, either decreases or increases in reaction times were observed, depending upon the animal. Lowered reaction times generally occurred immediately following the 1st day's cocaine injection, and continued through all subsequent days during the dose administration period, suggesting little development of tolerance or sensitivity to these reaction-time effects. Reaction-time decreases showed a U-shaped dose-effect function. The greatest decreases in reaction times occurred from 0.32 to 1.0 mg/kg, and produced an average reaction-time decrease of 10 to 12%. Concurrently measured auditory and visual thresholds showed no systematic changes as a function of cocaine dose. Pausing was observed during performance of the psychophysical tasks, with the length of total session pause times being directly related to cocaine dose.     

The effects of hand and direction parameter preknowledge on choice reaction times

The two studies undertaken investigated how reaction times are affected by preknowledge concerning hand and direction parameters, and the order in which these data are disclosed. In the first experiment, preknowledge was manipulated by selecting 2-CRT pairs which had either a common hand or direction component. Reaction signal information content (as defined by the number of unknown response parameters) was controlled, but no parameter differences emerged. When parameter order was manipulated by sequential precuing, the ‘hand then direction’ order conferred a significant advantage. Motor preparation and response selection explanations for this effect are considered. Various difficulties with the paradigms used are discussed, including those of distinguishing between response selection and motor programming contributions, controlling and inferring the strategies adopted by subjects, and defining task difficulty. The prospects for independently fostering either response identification or motor preparation by means of an appropriate selection of precues are also discussed.     

Inconsistency in serial choice decision and motor reaction times dissociate in younger and older adults

Intraindividual variability (inconsistency) in reaction time (RT) latencies was investigated in a group of younger (M=25.46 years) and older (M=69.29 years) men. Both groups performed 300 trials in 2-, 4-, and 8-choice RT conditions where RTs for decision and motor components of the task were recorded separately. A dissociation was evident in that inconsistency was greater in older adults for decision RTs when task demands relating to the number of choices and fatigue arising from time-on-task were high. For younger persons, a weak trend toward greater inconsistency in motor RTs was evident. The results are consistent with accounts suggesting that inconsistency in neurobiological mechanisms increases with age, and that attentional lapses or fluctuations in executive control contribute to RT inconsistency.     

Macroscopic thermodynamics of reaction times

I present a new interpretation of reaction time (RT) data from behavioural experiments. From a physical perspective, the entropy of the RT distribution–the temporal entropy–provides a model-free estimate of the amount of processing performed by the cognitive system. This new measure shifts the focus from the conventional interpretation of RTs being either long or short, into their distribution being more or less complex in terms of entropy. I introduce the formulation of the theory, followed by an empirical test using a large database of human RTs in lexical processing tasks. Using the measure, I obtain estimates of the processing loads to individual stimuli (i.e., words), as well as estimates for the overall rate at which the system processes information in these tasks. The relation between the temporal entropy and the RTs can be captured by a simple linear equation. I argue that this equation constitutes the equivalent of a ‘phase diagram’ of a task, providing indications about the different mechanisms that are at play in it, and locating critical points signalling the transitions between these different mechanisms. The results suggest an adaptive system that adjusts its operational processing speed to the demands of each individual stimulus. This finding is in contradiction with a generalization of Hick’s Law positing a relatively constant processing speed within an experimental context.     

Warned reaction times of sociopaths

A warned reaction time (RT) task was employed with eight male sociopaths and eight normal male Ss. A warning light appeared at a variable interval preceding a light to which the S responded with a key press. All Ss received both a regular and an irregular series with warning intervals of 1, 2, 4, 8, and 16 sec. In the regular series, blocks of intervals were presented in an ascending order. In the irregular series each interval followed every other interval equally often. Sociopaths obtained reliably slower RTs than did control Ss, showing a constant decrement across all intervals in the two kinds of series.     

Temporal characteristics of the surprise reaction induced by schema-discrepant visual and auditory events

Abstract

Two experiments investigated the effects of a schema-discrepant event on the surprise reaction. Schema-discrepancy concerned a physical feature of irrelevant distractor words that were presented while the subjects performed a choice reaction time task. The stimulus onset asynchrony (SOA) between the distractors and the task-relevant stimuli was manipulated in both experiments. The occurrence of the schema-discrepant event led to subjective feelings of surprise and enhanced recall of the stimulus material. In Experiment 1, the presentation of a schema-discrepant auditory event resulted in a pronounced increase of reaction time (RT) with a 0.2sec SOA but not with a 1.5sec SOA. In Experiment 2, the effects of both fixed and variable SOAs of four different lengths (simultaneous onset, 0.5sec, 1sec, or 2sec SOA) were investigated within a visual task context. The increase of RT was found to be most pronounced with SOAs of 0.5sec and lsec respectively, and more pronounced with variable than with fixed SOAs, especially with a simultaneous onset. These results provide information about the temporal characteristics of the inhibitory component of the surprise reaction, and suggest that the inhibitory effects of surprise depend considerably on the subjects' state of preparation for the experimental task.     

Late reaction times identify MCI

A group of 172 mild cognitive impairment (MCI) patients and 79 healthy control participants (HC) were tested on simple reaction time (SRT). There was a significant difference between MCI and HC in mean SRT. The test could be partitioned into five segments of 16 trials each, but RT's were not always available for each partition. However, scores from each segment for 166 MCI and 41 of the HC's were available. These data showed that a significant interaction between RT‐partition and diagnostic category was the main source of the difference between groups. The interaction indicated that MCI patients performed at about the same level as HC in the initial three of the five segments of the test, but were significantly impaired during the last two segments of the 80 trials. The results were interpreted as impaired sustained attention among a large part of the MCI group, and the study shows the importance of taking into account all avaliable data resulting from this type of test.     

Learning and locomotor reaction times

To help measure contributions by learning to latencies of complex locomotor responses, an operant stimulus-response unit was constructed and timed during human treadmill walking. A light flash served as discriminative stimulus (Sd) to produce electromyographic activity (EMG) of predefined filtered amplitude and duration by the leg muscle, rectus femoris (RF). A computer scored every EMG as successful or not (indicated by a high or low tone, respectively). The EMG burst also had to occur within successively shorter performance durations (PDUR), to a criterion of 80% successful responses. Among six adults, the shortest estimated reaction time was 110 msec. Relative strength of the operant unit was measured in relation to RF activity that occured in non-light step cycles or that was a by-product of the reinforcement regimen. It was proposed that operant latencies, after being minimized by specific conditioning regimens, can permit accurate timing of intervening neural events.     

Temporal resolution of the aging tactile sensory system

Oral and nonoral tactile fusion thresholds were obtained for 39 subjects ranging in age from 12 to 76 yr. Regression analysis of the data indicated a trend for fusion thresholds to become poorer with age. Further statistical testing indicated mean threshold and variability differences between subjects when they were placed into four groups according to age.     

Methodological issues in measures of imitative reaction times

Ideomotor (IM) theory suggests that observing someone else perform an action activates an internal motor representation of that behaviour within the observer. Evidence supporting the case for an ideomotor theory of imitation has come from studies that show imitative responses to be faster than the same behavioural measures performed in response to spatial cues. In an attempt to replicate these findings, we manipulated the salience of the visual cue and found that we could reverse the advantage of the imitative cue over the spatial cue. We suggest that participants utilised a simple visuomotor mechanism to perform all aspects of this task, with performance being driven by the relative visual salience of the stimuli. Imitation is a more complex motor skill that would constitute an inefficient strategy for rapid performance.