Sequential effects within a short foreperiod context: evidence for the conditioning account of temporal preparation

Responses to an imperative stimulus (IS) are especially fast when they are preceded by a warning signal (WS). When the interval between WS and IS (the foreperiod, FP) is variable, reaction time (RT) is not only influenced by the current FP but also by the FP of the preceding trial. These sequential effects have recently been proposed to originate from a trace conditioning process, in which the individuals learn the temporal WS-IS relationship in a trial-by-trial manner. Research has shown that trace conditioning is maximal when the temporal interval between the conditioned and unconditioned stimulus is between 0.25 and 0.60 s. Consequently, one would predict that sequential effects occur especially within short FP contexts. However, this prediction is contradicted by Karlin [Karlin, L. (1959). Reaction time as a function of foreperiod duration and variability. Journal of Experimental Psychology, 58, 185-191] who did not observe the typical sequential effects with short FPs. To investigate temporal preparation for short FPs, three experiments were conducted, examining the sequential FP effect comparably for short and long FP-sets (Experiment 1), assessing the influence of catch trials (Experiment 2) and the case of a very dense FP-range (Experiment 3) on sequential FP effects. The results provide strong evidence for sequential effects within a short FP context and thus support the trace conditioning account of temporal preparation.     

Reweighting sequential effects across different distributions of foreperiods: segregating elementary contributions to nonspecific preparation

In the study of nonspecific preparation, the response time (RT) to an imperative stimulus is analyzed as a function of the foreperiod (FP), the interval between a warning stimulus and the imperative stimulus. When FP is varied within blocks of trials, a downward sloping FP-RT function is usually observed. The slope of this function depends on the distribution of FPs (the more negative the skewness, the steeper the slope) and on intertrial sequences of FP (the longer the FP on the preceding trial, the steeper the slope). Because these determinants are confounded, we examined whether FP-RT functions, observed under three different FP distributions (i.e., uniform, exponential, and peaked) can be predicted, one from the other, by reweighting sequential effects. It turned out that reweighting explained very little variance of the difference between the FP-RT functions, suggesting a dominant role of temporal orienting strategies.     

The time-course of preparation with regular and irregular foreperiods

A previous experiment (Bertelson, 1967) had shown that the temporal information brought by a warning signal affected RT even after very short foreperiods (FPs). The present experiment was carried out to examine whether this result was contingent on the predictability of the FP. After a 5 sec. waiting delay, the subject heard a warning click which was followed after a predictable (regular procedure) or unpredictable FP (irregular procedure) by the visual signal calling for a choice reaction. The range of FPs was 0-300 msec, again. The time course of the adjustments triggered by the click was found to be similar under both procedures. The main conclusion is that a shift from preparation to reaction can occur at any time and need not be programmed before preparation is started.     

准备时间和预先信息对任务切换的影响

两个实验采用任务线索范式,考察了准备时间和预先信息对任务切换的影响。实验1的准备时间为可预测,实验2的为不可预测,以考察准备时间的可预测性对任务切换的影响。以被试执行重复任务、切到任务和切离任务的正确反应时为主要指标,结果：（1）在准备时间可预测和不可预测两种条件下,准备时间和预先信息之间存在显著交互作用。在可预测条件中,重复和切到任务的反应时随着准备时间的增加而减少,但切到代价无显著变化,切离任务的反应时不受准备时间的影响,切离代价表现出反准备效应;不可预测条件下,三种任务的反应时都随着准备时间的增加而减少,但是切到和切离代价表现出反准备效应;（2）切离任务的反应时和代价显著高于切到任务的反应时和代价;（3）在这两种条件下,都没有出现切换代价的准备效应     

Change in intraindividual variability over time as a key metric for defining performance-based cognitive fatigability

Cognitive fatigability is conventionally quantified as the increase over time in either mean reaction time (RT) or error rate from two or more time periods during sustained performance of a prolonged cognitive task. There is evidence indicating that these mean performance measures may not sufficiently reflect the response characteristics of cognitive fatigue. We hypothesized that changes in intraindividual variability over time would be a more sensitive and ecologically meaningful metric for investigations of fatigability of cognitive performance. To test the hypothesis fifteen young adults were recruited. Trait fatigue perceptions in various domains were assessed with the Multidimensional Fatigue Index (MFI). Behavioral data were then recorded during performance of a three-hour continuous cued Stroop task. Results showed that intraindividual variability, as quantified by the coefficient of variation of RT, increased linearly over the course of three hours and demonstrated a significantly greater effect size than mean RT or accuracy. Change in intraindividual RT variability over time was significantly correlated with relevant subscores of the MFI including reduced activity, reduced motivation and mental fatigue. While change in mean RT over time was also correlated with reduced motivation and mental fatigue, these correlations were significantly smaller than those associated with intraindividual RT variability. RT distribution analysis using an ex-Gaussian model further revealed that change in intraindividual variability over time reflects an increase in the exponential component of variance and may reflect attentional lapses or other breakdowns in cognitive control. These results suggest that intraindividual variability and its change over time provide important metrics for measuring cognitive fatigability and may prove useful for inferring the underlying neuronal mechanisms of both perceptions of fatigue and objective changes in performance.     

Decomposition of warning effects in Parkinson's disease

ABSTRACT

Neutral warning signals speed voluntary reactions by reducing temporal uncertainty and by triggering a brief burst of arousal. We attempted to isolate the phasic arousal mechanism in people with Parkinson's disease (PD) using a clock display to minimize temporal uncertainty. In this condition, the speeding of responses in a color-discrimination task by an accessory stimulus was the fully equivalent to the effect in age-matched control subjects. This indicates preserved phasic arousal in PD. Temporal preparation based on warning cues also appeared to be normal. By contrast, in a condition with high temporal uncertainty, the accessory stimulus (an air puff to the foot) impaired accuracy for the patients but not the neurologically normal subjects. The data are consistent with the view that PD disrupts internal but not external control of alertness.     

The effective time course of preparation

In reaction time (RT) research on nonspecific preparation, the preparation period is often identified with the foreperiod (FP), the interval between the offset of a neutral warning stimulus (S1) and the onset of the reaction stimulus (S2). However, the “effective preparation period” may be longer than FP: nonspecific preparation may start prior to FP (e.g., at the onset of S1) and/or continue after it (i.e., in parallel with the reaction process). In four experiments, we factorially varied FP and an additional factor (S1-duration; S2-luminance; stimulus–response compatibility) that probed the effective preparation period outside the bounds of FP. By examining how equivalent RT–FP functions obtain at the different levels of the additional factor, we showed that nonspecific preparation (1) starts at the onset of S1 for brief FPs but at its offset for longer FPs and (2) continues in parallel with S2-encoding but stops prior to response selection.     

Dissociations between reaction times and temporal order judgments: a diffusion model approach

A diffusion model for simple reaction time (RT) and temporal order judgment (TOJ) tasks was developed to account for a commonly observed dissociation between these 2 tasks: Most stimulus manipulations (e.g., intensity) have larger effects in RT tasks than in TOJ tasks. The model assumes that a detection criterion determines the level of sensory evidence needed to conclude that a stimulus has been presented. Analysis of the performance that would be achieved with different possible criterion settings revealed that performance was optimal with a lower criterion setting for the TOJ task than for the RT task. In addition, the model predicts that effects of stimulus manipulations should increase with the size of the detection criterion. Thus, the model suggests that commonly observed dissociations between RT and TOJ tasks may simply be due to performance optimization in the face of conflicting task demands.     

Prepared movements are elicited early by startle

A startle stimulus has been shown to elicit a ballistic response in a reaction time (RT) task at very short latencies without involvement of the cerebral cortex (J. Valls-Sole, J. C. Rothwell, F. Gooulard, G. Cossu, & E. Munoz, 1999). The present authors examined the nature of the startle response. A simple RT task was used in which 8 participants performed arm extension movements to 3 target distances (20 degrees, 40 degrees, and 60 degrees ) in a blocked design. An unpredictable startling acoustic stimulus (124 dB) replaced the imperative stimulus in certain trials. The authors verified the presence of a startle response independent from the prepared response by observing electromyographic (EMG) activity in sternocleidomastoid and orbicularis oculi muscles. Findings indicated that when the participant was startled, the intended voluntary response was produced at significantly shorter response latencies. Furthermore, the kinematic variables of the observed response during startle trials for all 3 target distances were mostly unchanged. The EMG characteristics of the responses were not modified, indicating that the response produced was indeed the prepared and intended response.     

Being prepared on time: on the importance of the previous foreperiod to current preparation, as reflected in speed, force and preparation-related brain potentials

How do participants adapt to temporal variation of preparatory foreperiods? For reaction times, specific sequential effects have been observed. Responses become slower when the foreperiod is shorter on the current than on the previous trial. If this effect is due to changes in motor activation, it should also be visible in force of responses and in EEG measures of motor preparation, the contingent negative variation (CNV) and the lateralized readiness potential (LRP). These hypotheses were tested in a two-choice reaction task, with targets occurring 500, 1500, or 2500 ms after an acoustic warning signal. The reaction time results showed the expected pattern and were accompanied by similar effects on a fronto-central CNV and the LRP. In contrast, the increase of response force with brief current foreperiods did not depend on previous foreperiods. Thus, EEG measures confirm that sequential effects on RT are at least partially due to changes in motor activation originating from previous trials. Effects found on response force may be related to general response readiness rather than activation of motor-hand areas, which may explain the absence of a sequential effect on force in the current experiment.     

The locus of temporal preparation effects: Evidence from the psychological refractory period paradigm

In reaction time (RT) tasks, responses are especially fast when participants can anticipate the onset of an imperative response signal. Although this RT facilitation is commonly attributed to temporal preparation, it is unclear whether this preparation shortens the duration of early or late processes. We used the effect propagation property of the psychological refractory period paradigm to localize the effect of temporal preparation. Manipulation of temporal uncertainty affected the RT of Task 1, regardless of the level of stimulus onset asynchrony (SOA). Consistent with the prediction of an early locus of temporal preparation, this effect propagated completely to the RT of Task 2 at short SOAs, but propagation diminished virtually to zero at long SOAs.     

Developmental dissociations of preparation over time: deconstructing the variable foreperiod phenomena

In a variable foreperiod (FP) paradigm, reaction times (RTs) decrease as a function of FP on trial n (FP effect) but increase with FP on trial n - 1 (sequential effects). These phenomena have traditionally been ascribed to different strategic preparation processes. According to an alternative explanation, common conditioning laws underlie both effects. The present study aims to disentangle these opposite views using a developmental perspective. In Experiment 1A, 4- to 11-year-old children and a control group of adults performed a simple RT task with variable FPs (1, 3, and 5 s). Furthermore, 12 4- to 5-year-old children were retested after 14 months (Experiment 1B). In Experiment 2, a narrower pool of participants (4, 5, and 6 years old) performed a variable FP paradigm with different FPs (1, 2, and 3 s). The results consistently suggest different ontogenetic time courses for the two effects: The sequential effects are already present in the youngest group (4-5 years old), whereas the FP effect appears gradually some years later. These findings are not fully compatible with previous views. A dual-process account is proposed to explain the data.     

The role of temporal unpredictability for process interference and code overlap in perception-action dual tasks

Two experiments explore interference in dual tasks. The first task required perceptual judgment of the movement direction (left vs right) of a briefly presented stimulus; the second task was a tone-discrimination reaction-time (RT) task. Participants reported their judgment at leisure. In 50% of the trials they were told to ignore the stimulus (no report). The directions of stimulus movement and response in the RT task could either be the same or different, establishing cross-task compatibility (CTC) relations. We varied the degree of temporal unpredictability by using two stimulus-onset asynchronies (SOA, 100 ms vs 1200 ms) for the task stimuli. In Experiment 1, SOA was varied randomly within blocks of trials in one group and between blocks in another group. In Experiment 2, only the short SOA was used in one group and only the long SOA in another group. In both experiments, we observed substantially longer RTs with the short compared with the long SOA, regardless of whether there was temporal certainty (blocked or constant SOA) or uncertainty (random SOA) about stimulus onset. We assume that the process of encoding into short-term memory in one task interferes with concurrent retrieval processes (i.e., response selection) in the other task. This process interference effect was strongly reduced in no-report trials. Furthermore, we found shorter RT in compatible than in incompatible trials. This CTC effect diminished with long SOA but occurred even in no-report trials, implying that it refers to an automatically activated and then decaying code that primes response selection in the RT task.     

Effects of a timing signal on simple reaction time with a rectangular distribution of foreperiods

It was hypothesized that the time course of preparation during a variable interstimulus interval (ISI) of a simple reaction time (RT) experiment was partly determined by the subjective distribution of conditional probabilities of the executive signal (ES). Sixty subjects performed a simple auditory RT task with various ranges of six ISI durations organized in rectangular frequency distributions. In order to give the subjects information about elapsed time during ISI, a recurring time-marking click, the periodicity of which was varied, was introduced during the ISI in one of the three series of trials each subject performed. A strong decreasing RT--ISI relationship was observed supporting the main hypothesis. However, a clear increase of mean RT over all ISIs combined, was also found. Because these two mixed effects were greatest when the click intervened at the possible times of ES occurrence only, three functions of time-information given by the click are discussed: (a) a reduction of the usual increase of time estimation error with increased ISI; (b) an increase of the subjects knowledge of the ISI range resulting from the discontinuity of the time-marking click which makes easier a discrete time-intervals numbering process; (c) a change of the simple-RT task into a discrimination task.     

Influence of an intertrial interval on sequential effects related to preparatory period duration for reaction time-task

In reaction time tasks, where the moment of occurrence of the response signal is uncertain, the temporal constraints of preparatory processes imply that subjects distribute their preparation during the preparatory period. The notion of cost of preparation has been proposed to explain the time course of these processes. This experiment was run to determine the effect of the cost of preparation on a serial-RT task and on a RT task where a rest interval of various possible durations (3, 6, or 9 sec.) is introduced. 12 subjects were tested. Data show that the amount spent on preparation during a trial affects the subject's performance during the next trials. But an hypothesis about memory search must also be advanced to explain the effect of the rest interval on the relationship of RT and the current preparatory period.     

Local muscular fatigue and attentional processes in a fencing task

Study of the effects of brief exercise on mental processes by Tomporowski and Ellis (1986) has shown that moderate muscular tension improves cognitive performance while low or high tension does not. Improvements in performance induced by exercise are commonly associated with increase in arousal, while impairments are generally attributed to the effects of muscular or central fatigue. To test two hypotheses, that (1) submaximal muscular exercise would decrease premotor time and increase would increase the attentional and preparatory effects observed in premotor time 9 men, aged 20 to 30 years, performed an isometric test at 50% of their maximum voluntary contraction between blocks of a 3-choice reaction-time fencing task. Analysis showed (1) physical exercise did not improve postexercise premotor time, (2) muscular fatigue induced by isometric contractions did not increase motor time, (3) there was no effect of exercise on attentional and preparatory processes involved in the postexercise choice-RT task. The invalidation of hypotheses was mainly explained by disparity in directional effects across subjects and by use of an exercise that was not really fatiguing.     

The effect of memory load on reaction time in character classification

In order to investigate the effect of memory load on reaction time (RT), choice RT trials were embedded in a binary character classification task using the varied set procedure. Twelve Ss performed in experimental blocks, as well as in control blocks consisting of character classification trials only. In experimental blocks, every trial began as a classification trial with the presentation of a new positive set. On a random half of these trials, however, a choice RT stimulus was presented instead of a probe letter and S simply made the indicated response. Results indicated that memory load had no effect on the choice RT trials. Embedding choice RT trials in the classification task affected the intercept (but not the slope) of the function relating classification RT to memory load. This result implies that the increase in latency usually obtained in classification experiments is entirely due to an increase in the duration of the memory searching stage of processing.     

Effects of sleep loss, time of day, and extended mental work on implicit and explicit learning of sequences

Tacit knowledge is part of many professional skills and can be studied experimentally with implicit-learning paradigms. The authors explored the effects of 2 different stressors, loss of sleep and mental fatigue, on implicit learning in a serial-response time (RT) task. In the 1st experiment, 1 night of sleep deprivation was shown to impair implicit but not explicit sequence learning. In the 2nd experiment, no impairment of both types of sequence learning was found after 1.5 hr of mental work. Serial-RT performance, in contrast, suffered from both stressors. These findings suggest that sleep deprivation induces specific risks for automatic, skill-based behavior that are not present in consciously controlled performance.     

Stimulus array onset as a preparatory signal in attentional selection

Warning signals enhance psychomotor performance by optimising preparation for the arrival of an event. Recent evidence, however, suggests that a warning signal can also disrupt attentional preparation by interfering with the process of preparing. It was hypothesised that a warning signal consisting of a change to the task-relevant items (array onset) may be more effective than a traditional warning signal consisting of the arrival, or removal, of a bar-cue which is independent of the task array. In three experiments array onset was a more effective warning signal than the bar-cue because reaction times were significantly faster without an increase in errors. In addition, an auditory warning signal resulted in faster reaction time than the bar-cue but in performance equivalent to that with an onset warning signal. Thus, the superiority of an auditory warning signal, reported by Davis and Green, was not found, when the interference of the visual warning signal with preparation was reduced. These results suggest that a visual warning signal consisting of a change to the stimulus array is more effective than an event independent from the stimulus array.     

The Space–Time Congruency Effect: A Meta‐Analysis

Several reaction time (RT) studies report faster responses when responses to temporal information are arranged in a spatially congruent manner than when this arrangement is incongruent. The resulting space–time congruency effect is commonly attributed to a culturally salient localization of temporal information along a mental timeline (e.g., a mental timeline that runs from left to right). The present study aims to provide a compilation of the published RT studies on this time–space association in order to estimate the size of its effect and the extent of potential publication bias in this field of research. In this meta‐analysis, three types of task are distinguished due to hitherto existing empirical findings. These findings suggest that the extent to which time is made relevant to the experimental task has a systematic impact on whether or not the mental timeline is activated. The results of this meta‐analysis corroborate these considerations: First, experiments that make time a task‐relevant dimension have a mean effect size of d = 0.46. Second, in experiments in which time is task irrelevant, the effect size does not significantly deviate from zero. Third, temporal priming studies have a surprisingly high mean effect size of d = 0.47, which, however, should be adjusted to d = 0.36 due to publication bias.