The relationship between estimates of foreperiod duration and simple time reaction

The relationship between estimates of foreperiod length and simple reaction time (RT) was examined using constant foreperiods. It was learned that neither the average accuracy nor the variability of the foreperiod estimates necessarily manifested themselves in appropriate simple RT change. Of secondary interest was the discovery that the average accuracy of foreperiod duration estimations differed greatly from that obtained for similar time lengths in a time-estimation task. Finally, an attempt was made to determine whether subjects actually utilized the directional knowledge of results inherent in the imperative stimulus to influence their foreperiod duration judgments. Unfortunately, the evidence obtained did not permit a definite answer regarding this possibility.     

Cardiac-somatic coupling during the foreperiod in a simple reaction-time task

The cardiac-somatic coupling hypothesis predicts a phasic decrease of general somatic behavior concomitant with a phasic heart-rate deceleration. This hypothesis was investigated during a constant 4 s foreperiod (FP) in a simple auditory reaction-time task. Intertrial interval duration was variable (mean 15.5 s; range 11–20 s). The response was a plantar flexion of the right foot. Besides ECG and EOG, surface EMG of nine striate muscles varying in relevance to response execution was recorded.In agreement with the hypothesis, heart rate, eye movements, and m. mylohyoideus EMG were decreased at the end of the FP. An increase in the EMG of the agonist m. soleus, antagonist m. tibialis anterior, m. peroneus longus, and m. trapezius was found during the FP. The activity in all other response-irrelevant muscles did not significantly differ from baseline. It was concluded that the results are at variance with the cardiac-somatic coupling hypothesis. Changes in surface EMG are discussed in terms of motor preparation.     

Energetic effects of stimulus intensity on prolonged simple reaction-time performance

The efficiency of cognition is modulated by energetic factors like effort, fatigue or circadian variation, which affect even the most basic cognitive operations. For instance, speeded detection in simple reaction-time (SRT) tasks usually slows down over time. The literature suggests that either mindlessness due to routinization or mental fatigue due to attentional resource depletion might underlie this decrement. We tested these assumptions in three 25-min visual SRT tasks using easy-to-detect high-intensity and hard-to-detect low-intensity stimuli presented in both blocked and mixed fashion. Mindlessness theory predicts that less monotonous stimulation (i.e. the mixed presentation) would mitigate the time-related decrement for high- and low-intensity stimuli alike, whereas resource-depletion theory predicts opposite effects of mixed presentation on high- versus low-intensity stimuli. Indeed, stimulus intensity and presentation mode cross-interacted significantly, indicating that the performance decline was steeper for high-intensity stimuli but less steep for low-intensity stimuli during mixed compared to blocked presentation, respectively. These results strongly suggest that the time-related efficiency decrement during prolonged SRT performance is related to accumulating mental fatigue. A conjecture is put forward that explains both resource depletion and mindlessness from the perspective of self-regulation. Our study underscores the need to incorporate energetic factors into models of cognition to facilitate their translation into real-world applications.     

The relation between physical stimulus properties and the effect of foreperiod duration on reaction time

Seven subjects were used in an experiment on the relation between signal modality and the effect of foreperiod duration (EP) on RT. With visual signals the usually reported systematic increase of RT as a function of FP duration (1, 5 and 15 s) was confirmed; with auditory signals no difference was found between FP's of 1 and 5 s while the effect at 15 s was equivalent to that found at 5 s with the visual signal. The results suggest that besides factors such as time uncertainty the FP effect is also largely dependent on the arousing quality of the signal.     

Sequential effects of foreperiod duration and conditional probability of the signal in a choice reaction time task

The aim of the present study was to determine whether the negative relationship usually found between reaction time and foreperiod duration in the variable foreperiod paradigm is entirely due to sequential foreperiod effects. It has been shown that when a particular foreperiod has been preceded by a longer one on the previous trial, reaction time is longer than when the preceding foreperiod was equal or shorter. This may be sufficient to explain the increase in reaction time observed for short foreperiods in variable foreperiod conditions.The present results show that, when sequential effects were controlled by the elimination of all trials where the foreperiod was shorter than the preceding one, the negative slope of the reaction time-foreperiod function diminished but did not disappear. The results suggest an interpretation of the role of conditional probability of stimulus arrival in terms of variation in the tendency to reprepare when the moment initially chosen for preparation appears to fall short of the moment at which the stimulus is actually presented.     

Visual signal detection and the locus of foreperiod effects

The effect of alertness on S's sensitivity to external signals was determined by varying the foreperiod in a visual signal detection task. Discriminability increased with increasing foreperiods up to an optimal foreperiod, beyond which it decreased slightly. This pattern of results parallels closely that of many foreperiod studies in which reaction time was the dependent variable. Because no speeded response was required in this signal detection task, it was concluded that alertness must be affecting an information processing stage prior to those associated with responding. Other evidence indicates that alertness does not affect sensory stages either. Alertness, by elimination, must be affecting the operation of a central stage, Posner's view of alertness which implicates the central stages is discussed.     

The relation between response-specificity, S-R compatibility, foreperiod duration and muscle-tension in a target aiming task

Three experiments are reported aiming at a further understanding of the effect of response-specificity, operationalized as the degree of commonality of direction of movements. In a previous study, Spijkers (1987) has claimed that response-specificity affects the readiness of the motor system and is not related to response-selection processes. These suppositions were generally confirmed in experiments 1 and 2 respectively. Common to both experiments were the variables average movement velocity and response-specificity. In experiment 1 the effect of the additional variable foreperiod duration was found to interact with that of response-specificity, hereby confirming its expected relation to the muscular system. The effect of response-specificity did not interact with that of spatial S-R compatibility in the second experiment, but also failed to show a main effect. The third experiment examined the supposed relation of response-specificity more directly through manipulation of the muscle-tension of the responding limb. The predicted form of the interaction between the effect of response-specificity and muscle-tension was confirmed which provided additional evidence for the interpretation of response-specificity effects in terms of differential muscular activation.     

VEP latency and some properties of simple motor reaction-time distribution

Summary The median of simple motor reaction (RT) to a flash parallels the latencies of visually evoked potential (VEP) deflections if flash intensity is varied. However, mean and median reaction times are not equal because of the skewness of RT distribution. It therefore seemed plausible that the mean reaction time — intensity relationship would be steeper than that for VEP latency. Such divergence would account for the intensity-dependent motor component of RT revealed by other psychophysical studies. The latencies of VEP deflections were measured as a function of intensity and the results were compared with mean and median RTs. The difference between mean and median RT is constant and independent of flash intensity. Moreover, both values are parallel to VEP latency. The general pattern of results remains the same after a change in the distribution from which the foreperiod is sampled.     

The investigation of ear asymmetry by simple and disjunctive reaction-time tasks

In a disjunctive reaction-time task in which Ss responded to clicks presented to one ear while white noise was presented to the other, RT was significantly faster to stimuli presented to the left ear than to the right ear. In a simple reaction-time task, using the same stimuli. there was no difference in R T to stimuli presented to right or left ear. The results were discussed in relation to functional asymmetry of the cerebral hemispheres. and were taken to support a perceptual interpretation of the ear asymmetry effect.     

On the relationship between stimulus intensity and duration of visible persistence

Stimulus intensity and duration of visible persistence have been found to vary directly in some studies but inversely in others. Hawkins and Shulman (1979) have proposed that this inconsistency can be resolved by separating the studies that employed a decrement-threshold measure of persistence (Type I measure) from those that measured the total duration of persistence (Type II measure). They suggested that Type I measures yield an inverse relationship, whereas Type II measures yield a direct relationship between intensity and persistence. Hawkins and Shulman's model is incomplete in ways that are easily remedied. However, the model is totally contradicted by the experimental evidence. A new resolution of the inconsistent results is proposed in terms of retinal afterimages.     

The effect of a cross-trial shift of auditory warning signals on the sequential foreperiod effect

When a warning signal (WS) precedes an imperative signal (IS) by a certain amount of time (the foreperiod, FP), responses are speeded. Moreover, this effect is modulated by the FP length in the previous trial. This sequential FP effect has lately been attributed to a trace-conditioning mechanism according to which individuals learn (and re-learn) temporal relationships between the WS and the IS. Recent evidence suggests that sensory WS attributes are critical to trigger time-related response activation. Specifically, when WS modality is shifted in subsequent trials (e.g., from auditory to visual modality), the sequential FP effect becomes attenuated. This study examined whether the sequential FP effect is reduced only by between-modality shifts or whether this attenuation generalizes to cross-trial shifts of WS attributes within modalities. We compared dimensional (low vs. high tone frequency) and qualitative shifts (pure tone vs. noise) of equal-intense auditory WS events. The results of four experiments revealed that shifts of tone frequency did not, whereas shifts of qualitative tone characteristics did attenuate the sequential FP effect. These results support the view that the WS acts as a trigger cue that unintentionally activates responses at previously reinforced critical moments.     

Dynamic adjustment of temporal preparation: Shifting warning signal modality attenuates the sequential foreperiod effect

We examined sequential effects in the variable foreperiod (FP) paradigm, which refer to the finding that responses to an imperative signal (IS) are fast when a short FP trial is repeated but slow when it is preceded by a long FP trial. The effect has been attributed to a trace-conditioning mechanism in which individuals learn the temporal relationship between a warning signal (WS) and the IS in a trial-by-trial manner. An important assumption is that the WS in a current trial (i.e., trial FP_n) acts as a conditioned stimulus, such that it automatically triggers the conditioned response at the exact critical moment that was imperative in the previous trial (i.e., trial FP_n−1). According to this assumption, a shift from one WS modality in trial FP_n−1 to another modality in trial FP_n is expected to eliminate or at least reduce the sequential FP effect. This prediction was tested in three experiments that included a random variation of WS modality and FP length within blocks of trials. In agreement with the prediction, a shift in WS modality attenuated the asymmetry of the sequential FP effect.     

Keeping Simon simple: Examining the relationship between sequential modulations and feature repetitions with two stimuli, two locations and two responses

The present study examined performance across three two-choice tasks that used the same two stimuli, the same two stimulus locations, and the same two responses to determine how task demands can alter the Simon Effect, its distribution across reaction time, and its sequential modulation. In two of the tasks, repetitions of stimulus features were not confounded with sequences of congruent and incongruent trials. This attribute allowed us to investigate the sequential modulation of the Simon Effect in a two-choice task while equalizing the occurrence of feature repetitions. All tasks showed a similar sequential modulation, suggesting that it is not driven by feature repetitions. Moreover, distributional analyses revealed that the advantage for congruent trials decreased as reaction time increased similarly following congruent and incongruent trials. Finally, a large increase in RT was observed when repeated responses were made to novel stimuli and when novel responses were made to repeated stimuli. This effect also showed a sequential modulation regardless of whether the stimulus repeated. The findings suggest that, even in two-choice tasks, response selection is mediated by complex, dynamic representations that encode abstract properties of the task rather than just simple features.     

The relationship between variability of intertap intervals and interval duration

Summary Subjects tracked intervals in a synchronization paradigm at interval durations of 180, 210, 240, 270, 300, 400, 500, 600, 700, 800, 900, and 1,000 ms. The variability of intertap intervals (ITIs) shows a sudden increase near 300 ms. This increase is interpreted as indicating the transition from automatic to controlled movement. It is suggested that the sudden change in the variability of ITIs does not reflect the operation of different timing mechanisms at short and long intervals, but differences in the way in which attentional processes come to bear on movement initiation for different interval durations. In contrast to previous findings reported in the literature, a U-shaped function between interval duration and variability in the 300-to-1,000-ms range was not observed.     

Stimulus variation and sequential judgements of duration

When a series of reproductions of an interval is made in the absence of a standard the judgements progressively lengthen. The similarity between stimulus conditions in this type of time estimation experiment and the conditions which produce a decrement in human vigilance is discussed. It is argued that failure to detect cues for the passage of time reduces the amount of time perceived to elapse. Reproduced judgements must consequently be increased in length to match remembered standards. The hypothesis is then made that the kind of variation in background stimulation which facilitates vigilance should increase the frequency of detection of cues for duration and reduce reproduced judgements. This hypothesis is tested with 80 subjects and a reversal of the serial reproduction effect is found on trials with changed background conditions.