Spatial attention and reaction times during smooth pursuit eye movement

To examine the spatial shift of attention during smooth pursuit, we measured reaction times (RTs) to a visual target that appeared during pursuit. Participants pursued a moving row of circular frames and responded to a target presented within one of the frames. The results showed large RT differences between stimulus velocities up to 5o/s and 10o/s or above. RTs were faster for a target appearing in the pursuit direction than for one in the opposite direction. When an auditory precue was presented, the RTs during pursuit at 10o/s were faster with increases in the stimulus onset asynchrony (SOA) between the cue and the target. Furthermore, RTs were faster in the cued than in the uncued direction. These results not only support the idea that RTs during pursuit reflect the operation of attention, but also suggest that attention during pursuit can be shifted by the abrupt onset of a target stimulus and/or by prior information regarding the onset of a target stimulus.     

Effects of walking on reaction and movement times among elders

The purpose of this study was to examine the effects of a 6-wk. walking program on reaction times and movement times among 52 elders. Twenty-seven elderly, whose mean age was 71.8 yr. comprised the experimental group, and 25 elderly whose mean age was 71.8 yr. comprised the comparison group. The former subjects walked for 30 min. three times a week for 6 wk. while the latter maintained their normal activity. No significant differences in simple or choice reaction times and the associated movement times were found. To clarify the relationship of health and current and past physical activity, correlations of these with both simple and choice reaction times and movement times were examined. Except for the number of miles walked in a week, none of the correlations were significant. These results may not support previous findings that reaction and movement times were shorter with life-long participation in aerobic activity. However, the present study examined persons who were sedentary and were not involved in a life-long participation in aerobic exercise. Implications of these findings are discussed.     

Structural complexity of motor patterns: A study on reaction times and movement times of handwritten letters

This study investigates the effects of psychomotor complexity on latencies for beginning to write single letters and numerals, and on times taken to complete the first strokes of letters and numerals. An experiment measured simple and choice reaction times for writing homogeneous graphemes (i.e., letters or numerals made up of similar strokes) and for writing heterogeneous graphemes (i.e., characters made up of dissimilar strokes). It was assumed that the motor programme for writing a letter is retrieved from long-term memory and briefly held, until it is used, in a short-term buffer store. The experiment examined the hypothesis that it is more difficult to read out homogeneous than heterogeneous stroke-structures from this store. For three out of four allographic grapheme pairs, homogeneous graphemes required longer initiation times or longer movement times for completion of the first stroke than did heterogeneous graphemes. These results are discussed in relation to recent findings on motor programming based on the use of reaction-time paradigms.     

Manual reaction times and error rates in stutterers.

In this study 18 stutterers and 18 nonstutterers were presented trials on which they should press a button as fast as possible, intermixed with trials which required no responding. Stutterers had slightly faster reaction times but also made slightly more errors, that is, they tended to press the button when they should not have done so. As neither difference was significant, it was concluded that stutterers did not differ from normal speakers in manual reaction speed, nor did they choose a different speed-accuracy trade-off criterion for the given task.     

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.     

Differential reinforcement of reaction times in developmental retardates.

The effects of differential reinforcement on reaction times to two intensities of reaction signal were investigated in 36 developmental retardates. One group was reinforced for reaction times to the higher intensity signal; a second group was reinforced for reaction times to the lower intensity signal; a third group received no reinforcement. Reaction time decreased as signal intensity increased and decreased over sessions as a function of reinforcement. Likewise, reinforcement either exaggerated or reversed differences in reaction times to each signal depending on the particular reinforcement contingency. Results were discussed in terms of attentional and motivational explanations of effects of signal intensity on reaction times of retardates.     

Contrast as seen in visual search reaction times.

Three pigeons searched arrays of alphabetic letters displayed on computer monitors. On each trial, either an A or an E appeared, and the reaction time and accuracy with which the bird pecked at this target were measured. In each block of trials, each target (A or E) was displayed alone, or together with a number of distractor letters (2 or 18) that varied in their similarity to the target. During a baseline series of sessions, responses to the A and to the E each yielded food reinforcement on 10% of the trials. In the next series of sessions, reinforcement continued at 10% for A, but rose to 30% for E. In a final series, these reinforcement conditions were reversed. As expected, reaction times increased with target-distractor similarity and (for similar distractors) with the number of distractors. Increased reinforcement of E had no effect on reaction times to E, but produced a very consistent increase in reaction times to A; the average increase was constant across the various display conditions. Reversal of the differential reinforcement conditions reversed this contrast effect. Analysis of the reaction time distributions indicated that increased reinforcement to E decreased the momentary probability of response to A by a constant amount, regardless of display conditions. These results are discussed in relation to theories of contrast, memory, and of the search image.     

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.     

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.     

Choice reaction times for temporal numerosity

Subjects watched rapidly presented visual sequences of two events until they decided which event was the more frequent. Accuracy was reduced both by increased rates of presentation and by the addition of more inconclusive information to the initial portion of the sequence. Response latencies were longest when there was no objective numerosity inbalance, and they decreased, for both correct responses and errors, when discrimination was relatively easy. The patterns of decision latencies for individual subjects could be represented on a continuum defined by the sensitivity of the latencies to the rate of event presentation and to the objective inbalance between the two events. The discussion points out formal and empirical similarities between sequential numerosity judgments and choice reaction times. The present results are discussed within the framework of a first-passage time model, to be developed formally in a subsequent paper.     

Choice reaction times for skilled responses

Two kinds of choice reaction time experiments are reported, both of which make use of a highly overlearned sensori-motor response. When a response is required for each stimulus presented, no increase in reaction time occurs as a function of the number of alternative stimuli available. It is proposed that the increase in choice reaction times commonly thought to accompany an increase in the number of alternative choices provided reflects the unpractised state of the responder. When a response is required for only one out of n possible stimuli, a slight but consistent increase in reaction time takes place with an increase in the number of alternatives. An analogy is drawn between the second experiment and a vigilance task and an expectancy hypothesis is invoked to explain the results.     

Computer control of grating phase and movement

A method is presented which uses an on-line computer to control the spatial phase and movement of an electronically generated grating display for visual experiments. This technique minimizes CPU overhead and is inexpensive. The method is compared with several other schemes for controlling grating phase and movement.     

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.     

Evaluating warning sound urgency with reaction times

It is well-established that subjective judgments of perceived urgency of alarm sounds can be affected by acoustic parameters. In this study, the authors investigated an objective measurement, the reaction time (RT), to test the effectiveness of temporal parameters of sounds in the context of warning sounds. Three experiments were performed using a RT paradigm, with two different concurrent visuomotor tracking tasks simulating driving conditions. Experiments 1 and 2 show that RT decreases as interonset interval (IOI) decreases, where IOI is defined as the time elapsed from the onset of one sound pulse to the onset of the next. Experiment 3 shows that temporal irregularity between pulses can capture a listener's attention. These findings lead to concrete recommendations: IOI can be used to modulate warning sound urgency; and temporal irregularity can provoke an arousal effect in listeners. The authors also argue that the RT paradigm provides a useful tool for clarifying some of the factors involved in alarm processing.     

Prism exposure aftereffects and direct effects for different movement and feedback times

The effects of movement time and time to visual feedback (feedback time) on prism exposure aftereffects and direct effects were studied. In Experiment 1, the participants' (N = 60) pointing limb became visible early in the movement (.2-s feedback time), and eye-head aftereffects increased with increasing movement time (.5 to 3.0 s), but larger hand-head aftereffects showed little change. Direct effects (terminal error during exposure) showed near-perfect compensation for the prismatic displacement (11.4 diopters) when movement time was short but decreasing compensation with longer movement times. In Experiment 2, participants' (N = 48) eye-head aftereffects increased and their larger hand-head aftereffects decreased with increasing movement time (2.0 and 3.0 s), especially when feedback time increased (.25 and 1.5 s). Direct effects showed increasing overcompensation for longer movement and feedback times. Those results suggest that aftereffects and direct effects measure distinct adaptive processes, namely, spatial realignment and strategic control, respectively. Differences in movement and feedback times evoke different eye-hand coordination strategies and consequent direct effects. Realignment aftereffects also depend upon the coordination strategy deployed, but not all strategies support realignment. Moreover, realignment is transparent to strategic control and, when added to strategic correction, may produce nonadaptive performance.     

Simple motor and phonemic processing reaction times of stutterers

Simple motor and phonemic processing reaction times were gathered for a group of stutterers and were compared to data obtained from normal speakers. The stutterers' responses were significantly more latent under both conditions. Such findings suggested that at least two neurophysiological factors influence stutterers' reaction-time latencies. These include aberrancies in both motor control and auditory processing capacity.     

Multidimensional scaling models for reaction times and same-different judgments

A method for joint analysis of reaction times and same-different judgments is discussed. A set of stimuli is assumed to have some parametric representation which uniquely defines dissimilarities between the stimuli. Those dissimilarities are then related to the observed reaction times and same-different judgments through a model of psychological processes. Three representation models of dissimilarities are considered, the Minkowski power distance model, the linear model, and Tversky's feature matching model. Maximum likelihood estimation procedures are developed and implemented in the form of a FORTRAN program. An example is given to illustrate the kind of analyses that can be performed by the proposed method.The work reported in this paper is supported by Grant A6394 to the first author from the Natural Sciences and Engineering Research Council of Canada. Portions of this study have been presented at the Psychometric Society meeting in Chapel Hill, N.C., in May, 1981. We thank Tony Marley, Jim Ramsay and anonymous reviewers for their helpful comments. MAXRT, a computer program which performs the computations described in this paper may be obtained by writing to the first author.     

Saccadic reaction times of dyslexic and age-matched normal subjects

Saccadic reaction times (SRT) were measured in a simple task: subjects had to make saccades from a central fixation point to peripheral targets, which appeared randomly 4 deg to the left or to the right. In the first test the fixation point went off before the target appeared (gap trials); in the second test it remained on the screen (overlap trials). The distribution of SRTs for trained normal adults (N = 4), untrained normal adults (N = 11), untrained normal children (aged 9-11 years, N = 9), untrained normal teenagers (aged 15-17 years, N = 8), dyslexic children (aged 9-11 years, N = 15), and dyslexic teenagers (aged 15-17 years, N = 5) were compared, with special emphasis on the number of express saccades, ie saccades with extremely short reaction times (100-120 ms, under the present conditions). In normal adults with the gap paradigm, the distribution of reaction times typically exhibits two or three modes (express saccades, fast regular saccades, and very few slow regular saccades), whereas in the overlap paradigm only one or two modes (few fast regular saccades and many slow regular saccades) are obtained. On average, normal children produce more express saccades than naive normal adults. Dyslexic children produce more express saccades than the normal age-matched controls. Among the dyslexic children, four different types of abnormalities in their reaction times were encountered. The group of dyslexic teenagers was characterized by a larger number of express saccades at the expense of fast regular saccades in gap trials and by fewer express saccades and fewer fast regular saccades in overlap trials when compared to the age-matched control group. It is concluded that the abnormal patterns of saccadic reaction times reflect defects in the system of visual attention and/or in its control over the oculomotor system, rather than indicating a defect in the oculomotor system itself. In this context, symptoms of dyslexia appear as a combination of attentional deficits and irregular timing of saccadic eye movements.