Variable Foreperiod Research Articles

Individual differences in working memory capacity and temporal preparation: A secondary reanalysis.

The ability to prepare and maintain an optimal level of preparedness for action, across some unknown duration, is critical for human behavior. Temporal preparation has historically been analyzed in the context of reaction time (RT) experiments where the interval varies between the start of the trial, or foreperiod (FP), and the required response. Two main findings have come out of such paradigms: the variable FP effect (longer RTs to shorter vs. longer FPs) and the sequential FP effect (longer RTs when shorter FPs follow longer FPs). Several theoretical views of these FP effects have been proposed with some suggesting a dissociation while others argue for an implicit process driven by memory traces. One possible method to test these views of FP effects is to examine how individual differences in working memory capacity (WMC) moderate such effects. To this end, I reanalyzed data from three studies in which participants completed measures of WMC and a simple RT task with a variable FP. Results suggest that individual differences in WMC were related to the magnitude of the variable FP and the sequential FP effect in two of three individual studies. A "mega-analysis" provided supportive evidence for a relationship between WMC and both forms of FP effects. The present combined experimental-individual differences study provides a novel approach to better understand how and why individuals vary in temporal preparation ability. Through leveraging several large-scale databases unseen in FP research, I provide a new way of understanding FP effects and response timing more generally.

Gazing into spatiotemporal ‘known unknowns’: the influence of uncertainty on pupil size and saccadic eye movements

Expectation of a future stimulus increases the preparedness to act once it actually appears and results in reduced latency of the appropriate motor response. Real world events are uncertain both spatially and/or temporally but this uncertainty could itself be expected. In the presence of both expected spatial and temporal uncertainty, which one should be prioritized by the motor system could depend on the context. Therefore, we investigated the relative weight of expected spatial and temporal uncertainty during the preparation of a saccadic eye movement. A reaction time task was used with a variable foreperiod between a warning and an imperative visual stimuli. Expected temporal and/or spatial uncertainty associated with the stimulus was cued. We found that before imperative stimulus onset, pupil dilation increased with expected temporal uncertainty but was unaltered by spatial uncertainty. After imperative stimulus onset, both types of expected uncertainty affected saccade latency. Maximum eye velocity was modulated by expected spatial uncertainty only. In conclusion, expected temporal and spatial uncertainty do not have the same impact on preparation and execution of a motor response. There could be a prioritization of the relevant information as a function of the evolving expected uncertainty context during the task.

On the nonlinearity of the foreperiod effect

One of the frequently employed tasks within the implicit timing paradigm is the foreperiod task. The foreperiod is the time interval spanning from the presentation of a warning signal to the appearance of a target stimulus, during which reaction time trajectory follows time uncertainty. While the typical approach in analyzing foreperiod effects is based on linear approximations, the uncertainty in the estimation of time, expressed by the Weber fraction, implies a nonlinear trend. In the present study, we analyzed the variable foreperiod reaction times from a relatively large sample (n = 109). We found that the linear regression on reaction times and log-transformed reaction times poorly fitted the foreperiod data. However, a nonlinear regression based on an exponential decay function with three distinctive parameters provided the best fit. We discussed the inferential hazards of a simplistic linear approach and demonstrated how a nonlinear formulation can create new opportunities for studies in implicit timing research, which were previously impossible.

Pupillary fluctuation amplitude preceding target presentation is linked to the variable foreperiod effect on reaction time in Psychomotor Vigilance Tasks.

Understanding temporally attention fluctuations can benefit scientific knowledge and real-life applications. Temporal attention studies have typically used the reaction time (RT), which can be measured only after a target presentation, as an index of attention level. We have proposed the Micro-Pupillary Unrest Index (M-PUI) based on pupillary fluctuation amplitude to estimate RT before the target presentation. However, the kind of temporal attention effects that the M-PUI reflects remains unclear. We examined if the M-PUI shows two types of temporal attention effects initially reported for RTs in the variable foreperiod tasks: the variable foreperiod effect (FP effect) and the sequential effect (SE effect). The FP effect refers to a decrease in the RT due to an increase in the foreperiod of the current trial, whereas the SE effect refers to an increase in the RT in the early part of the foreperiod of the current trial due to an increase in the foreperiod of the previous trial. We used a simple reaction task with the medium-term variable foreperiods (Psychomotor Vigilance Task) and found that the M-PUI primarily reflects the FP effect. Inter-individual analyses showed that the FP effect on the M-PUI, unlike other eye movement indices, is correlated with the FP effect on RT. These results suggest that the M-PUI is a potentially powerful tool for investigating temporal attention fluctuations for a partly unpredictable target.

Children with developmental dyslexia show an increased variable foreperiod effect

ABSTRACT Dyslexia has been linked to timing deficits by previous studies. Here, we investigated specifically two types of implicit temporal adaptation abilities in children with dyslexia, namely the variable foreperiod effect and time-based expectancy. Eighteen children with dyslexia and eighteen typically developing children with ages ranging from 8 to 13 participated. They completed a binary choice reaction time task in which short (1,000 ms) or long (3,000 ms) durations of a visual cue (i.e. foreperiod) predicted with a probability of .9 the direction of a centrally presented arrow. Dyslexic children showed a significantly more pronounced variable foreperiod effect (i.e. responding faster to long foreperiods than to short foreperiods) than normally developing children. However, there were no significant differences between groups in the time-based expectancy effect (i.e. responding differently to likely combinations of foreperiod and target than to unlikely combinations). The results are discussed in the context of time-deficit theories of dyslexia.

Implicitly learning when to be ready: From instances to categories

There is growing appreciation for the role of long-term memory in guiding temporal preparation in speeded reaction time tasks. In experiments with variable foreperiods between a warning stimulus (S1) and a target stimulus (S2), preparation is affected by foreperiod distributions experienced in the past, long after the distribution has changed. These effects from memory can shape preparation largely implicitly, outside of participants’ awareness. Recent studies have demonstrated the associative nature of memory-guided preparation. When distinct S1s predict different foreperiods, they can trigger differential preparation accordingly. Here, we propose that memory-guided preparation allows for another key feature of learning: the ability to generalize across acquired associations and apply them to novel situations. Participants completed a variable foreperiod task where S1 was a unique image of either a face or a scene on each trial. Images of either category were paired with different distributions with predominantly shorter versus predominantly longer foreperiods. Participants displayed differential preparation to never-before seen images of either category, without being aware of the predictive nature of these categories. They continued doing so in a subsequent Transfer phase, after they had been informed that these contingencies no longer held. A novel rolling regression analysis revealed at a fine timescale how category-guided preparation gradually developed throughout the task, and that explicit information about these contingencies only briefly disrupted memory-guided preparation. These results offer new insights into temporal preparation as the product of a largely implicit process governed by associative learning from past experiences.

Temporal preparation in adults with autistic spectrum disorder: The variable foreperiod effect.

Research suggested the possibility that temporal cognition may be different in autistic spectrum disorder (ASD). Although there are some empirical studies examining timing ability in these individuals, to our knowledge, no one directly assessed the ability to predict when an event will occur. Here, we report a study on implicit temporal preparation in individuals with ASD as indexed by the variable foreperiod (FP) effect. We compared a group of adult ASD participants to a group of typically-developed (TD) controls, for their respective abilities to utilize implicit temporal information in a simple detection task with three different preparatory intervals (FP, short, middle and long). Participants were given a warning tone to signal an imminent stimulus, and asked to press a key as quickly as they could upon detection of the stimulus. Both groups were able to use implicit temporal information, as revealed by both the variable-FP effect (i.e., faster response for targets appearing after a long FP) and asymmetric sequential effects (i.e., slower response in short-FP trials following a previous long-FP trial). The TD group exhibited a faster response in a long-FP trial that was preceded by short-FP one, whereas the ASD group did not, as reflected in their higher percentage of response omissions for a target that appeared later than in the previous trial. The reduced ability of ASD participants to modulate their responses under these conditions might reflect a difficulty in time-based monitoring of stimulus occurrence. LAY SUMMARY: Time-processing may be different in autistic spectrum disorder (ASD). This study addressed the ability to anticipate a relevant stimulus's onset according to predictable interstimulus intervals comparing adults with ASD and typically developed controls. We found that ASD participants did not benefit from temporal preparation when stimulus appeared later than previously attended. This suggests a reduced ability in detecting implicit temporal regularities between events.

Temporal productions in a variable environment: timing starts from stimulus identification rather than onset

Timing an interval is integral in everyday life, from crossing a street or boiling an egg to playing sports and chatting with friends. In the current article, participants were asked to produce durations ranging from 500 to 1250ms by either terminating an automatically initiated duration, or by maintaining a key press. When participants expected this production to start was manipulated using a variable foreperiod. Further, between subjects, the durations required for production were either variable or constant within a block. Together, these manipulations set up a temporally-and event-uncertain environment. When participants both initiated and terminated an interval, the uncertainty of the environment did not systematically affect productions. However, when productions were only terminated, productions were longer and given more uncertainty. While the effects of timing onset could be attributed to when a participant registers a stimulus, the effects of uncertainty with regards to what duration would be required for production indicates that participants appear to register what a stimulus is prior to initiating their timing. This finding indicates that timing may relate to when a stimulus is identified, rather than when it is first perceived. Alternatively, perhaps the onset of timing is postponed by event uncertainty.

Dissociating cholinergic influence on alertness and temporal attention in primates in a simple reaction time paradigm.

The ability to promptly respond to behaviourally relevant events depends on both general alertness and phasic changes in attentional state driven by temporal expectations. Using a variable foreperiod simple reaction time (RT) task in four adult male rhesus macaques, we investigated the role of the cholinergic system in alertness and temporal expectation. Foreperiod effects on RT reflect temporal expectation, while alertness is quantified as overall response speed. We measured these RT parameters under vehicle treatment and systemic administration of the muscarinic receptor antagonist scopolamine. We also investigated whether and to what extent the effects of scopolamine were reversed by donepezil, a cholinesterase inhibitor widely used for the treatment of dementia. In the control condition, RT showed a continuous decrease as the foreperiod duration increased, which clearly indicated the effect of temporal expectation on RT. This foreperiod effect was mainly detectable on the faster tail of the RT distribution and was eliminated by scopolamine. Furthermore, scopolamine treatment slowed down the average RT. Donepezil treatment was efficient on the slower tail of the RT distribution and improved scopolamine-induced impairments only on the average RT reflecting a general beneficial effect on alertness without any improvement in temporal expectation. The present results highlight the role of the cholinergic system in temporal expectation and alertness in primates and help delineate the efficacy and scope of donepezil and other cholinomimetic agents as cognitive enhancers in present and future clinical practice.

Associative learning of response inhibition affects perceived duration in a subsequent temporal bisection task

Interval timing, the ability to discern the duration of an event, is integral to appropriately navigating the world, from crossing the road to catching a ball. Several features of an event can affect its perceived duration, for example it has previously been shown that a large stimulus is perceived to last longer than a small stimulus. In the current article, participants performed either a Go/No-Go or variable foreperiod task prior to performing a temporal bisection task. In both the Go/No-Go and variable foreperiod tasks, participants learned an association between a particular response and a particular stimulus. Subsequently, the perceived duration of these stimuli was tested in a temporal bisection task. Our findings indicated that associating a stimulus with response inhibition (i.e. a No-Go stimulus) decreased perceived duration compared to a stimulus associated with a response (a Go stimulus). Associating a stimulus with either a short or long foreperiod, on the other hand, did not affect perceived duration. We relate this finding back to the coding efficiency theory and the processing principle. A No-Go stimulus requires more cognitive processing than a Go stimulus and would thus be predicted to increase, rather than decrease, perceived duration in both these time perception theories. Finally, we suggest how our findings might be used in future investigations of interval timing.

Learning from the past and expecting the future in Parkinsonism: Dopaminergic influence on predictions about the timing of future events

The prolonged reaction times seen in Parkinson's disease (PD) have been linked to a dopaminergic-dependent deficit in using prior information to prepare responses, but also have been explained by an altered temporal processing. However, an underlying cognitive mechanism linking dopamine, temporal processing and response preparation remains elusive.To address this, we studied PD patients, with or without medication, and age-matched healthy individuals using a variable foreperiod task requiring speeded responses to a visual stimulus occurring at variable onset-times, with block-wise changes in the temporal predictability of visual stimuli.Compared with controls, unmedicated patients showed impaired use of prior information to prepare their responses, as reflected by slower reaction times, regardless of the level of temporal predictability. Crucially, after dopamine administration normal performance was restored, with faster responses for high temporal predictability.Using Bayesian hierarchical drift-diffusion modelling, we estimated the parameters that determine temporal preparation. In this theoretical framework, impaired temporal preparation under dopaminergic depletion was driven by inflexibly high decision boundaries (i.e. participants were always extremely cautious). This indexes high levels of uncertainty about temporal predictions irrespectively of stimulus onset predictability.Our results suggest that dopaminergic depletion in PD affects the uncertainty of predictions about the timing of future events (temporal predictions), which are crucial for the anticipatory preparation of responses. Dopamine, which is affected in PD, controls the ability to predict the timing of future events.

Motivation alters implicit temporal attention through sustained and transient mechanisms: A behavioral and pupillometric study.

Temporal expectations aid performance by allowing the optimization of attentional readiness at moment of highest target probability. Reward enhances cognitive performance through its action on preparatory and reactive attentional processes. To elucidate how motivation interacts with mechanisms of implicit temporal attention, we studied healthy young adult participants (N=73) performing a sustained attention task with simultaneous pupillometric recording, under different reward conditions (baseline: 0 c; reward: 10 c/fast response). Target timing was temporally unpredictable (variable foreperiod: 2-10s, uniformly distributed), in which case implicitly formed timing expectations. Trials were binned according to current foreperiod (FPn ; short: 2-6s; long: 6-10s) and preceding foreperiod (FPn-1 ; short: 2-6s; long: 6-10s). Overall, performance data showed the expected temporal attention effects, with slower responses after shorter FPn s, particularly when they followed longer FPn-1 s. Moreover, these temporal effects were significantly reduced in the reward condition. While performance improved in all trial types, the largest benefit appeared in trials that were normally most disadvantaged by invalid temporal expectation. Furthermore, reward motivation was accompanied by an increase in sustained (prestimulus) and transient (poststimulus response) pupil diameter. The latter effect was particularly evident following short FPn s. The current findings suggest that reward motivation can improve overall attentional performance and reduce implicit temporal bias, both through preparatory and reactive attentional mechanisms.

Timing of Gun Fire Influences Sprinters' Multiple Joint Reaction Times of Whole Body in Block Start.

Experienced sprinters are specifically adapted to pre-planning an advanced motor program. Herein, sprinters are able to immediately accelerate their center of mass forward with a whole-body coordinated motion, following a steady state crouched position. We examined the effect of variable timing of reaction signals on multiple joint reaction times (RT) and whole-body RT for specialist sprinters. Twenty well-experienced male sprinters performed five start-dashes from a block start under five variable foreperiod (FP) length conditions (1.465, 1.622, 1.780, 1.938, and 2.096 s), with trials randomly timed between a warning and an imperative tone. Participants’ sprinting motion and ground reaction forces of their four limbs during the block start were measured simultaneously. Whole-body RT was significantly shorter when FP length was longer; the values of whole-body RT were 117 ± 5 ms, 129 ± 5 ms, 125 ± 4 ms, 133 ± 6 ms, and 156 ± 8 ms in the 2.096, 1.938, 1.780, 1.622, and 1.465-s FP-length conditions, respectively. A repeated-measures analysis of variance found a significant joint-by-FP length interaction in joint-moment RT. These findings suggest that FP length affects coordinated motion in four limbs and whole-body RT. This information will be able to lead to new methods for start signals in sprint running events and advance our understanding of the association between FP length and dynamic coordinated motion.

Comparative analysis of choice reaction times with randomly variable foreperiods in normal individuals and schizophrenic patients

Background: Reaction time (RT) is an index of brain’s biological efficiency. RT can indicate sensorimotor variability with varying foreperiods (FPs) and can indicate mental dysfunction like schizophrenia. Aims and Objective: Objective was to analyze the effect variable FPs on RTs in controls and schizophrenic patients. Materials and Methods: The study was conducted at Topiwala National Medical College, Mumbai, on 80 normal controls and 80 schizophrenic patients in the age group of 20-50 years. Digital RT apparatus (RTM-608) manufactured by Bio-Tech., with a maximum resolution time of 0.0001 s was used. Auditory RT (ART) and visual RT (VRT) with randomly variable FPs (2, 4, and 6 s) were recorded in controls and schizophrenic patients. Results: Two-way ANOVA with replication in MS Office Excel was used to analyze results. ARTs and VRTs in schizophrenic patients were significantly slower than that in controls with P = 1.4336E-215 with F = 6779.53969 and P = 2.5966E-209 with F = 6161.152654, respectively. The condition effect was also significant with ARTs and VRTs, increasing in patients with increase in the FPs with P = 4.84285E-16 with F = 73.35131426 (ART) and P = 2.72532E-14 with F = 63.68037666 (VRT), respectively. The Group X condition interaction also was significant with P = 8.80207E-12 with F = 50.27084108 in case of ARTs and P = 1.21054E-10 with F = 44.36301991 in case of VRTs. Conclusion: This shows that variation in FPs results in slower RTs in schizophrenic patients than in controls.

Perturbation Predictability Can Influence the Long-Latency Stretch Response.

Perturbations applied to the upper limbs elicit short (M1: 25–50 ms) and long-latency (M2: 50–100 ms) responses in the stretched muscle. M1 is produced by a spinal reflex loop, and M2 receives contribution from multiple spinal and supra-spinal pathways. While M1 is relatively immutable to voluntary intention, the remarkable feature of M2 is that its size can change based on intention or goal of the participant (e.g., increasing when resisting the perturbation and decreasing when asked to let-go or relax following the perturbation). While many studies have examined modulation of M2 between passive and various active conditions, through the use of constant foreperiods (interval between warning signal and a perturbation), it has also been shown that the magnitude of the M2 response in a passive condition can change based on factors such as habituation and anticipation of perturbation delivery. To prevent anticipation of a perturbation, most studies have used variable foreperiods; however, the range of possible foreperiod duration differs between experiments. The present study examined the influence of different variable foreperiods on modulation of the M2 response. Fifteen participants performed active and passive responses to a perturbation that stretched wrist flexors. Each block of trials had either a short (2.5–3.5 seconds; high predictability) or long (2.5–10.5 seconds; low predictability) variable foreperiod. As expected, no differences were found between any conditions for M1, while M2 was larger in the active rather than passive conditions. Interestingly, within the two passive conditions, the long variable foreperiods resulted in greater activity at the end of the M2 response than the trials with short foreperiods. These results suggest that perturbation predictability, even when using a variable foreperiod, can influence circuitry contributing to the long-latency stretch response.

The Role of Dopamine in Temporal Uncertainty.

The temporal preparation of motor responses to external events (temporal preparation) relies on internal representations of the accumulated elapsed time (temporal representations) before an event occurs and on estimates about its most likely time of occurrence (temporal expectations). The precision (inverse of uncertainty) of temporal preparation, however, is limited by two sources of uncertainty. One is intrinsic to the nervous system and scales with the length of elapsed time such that temporal representations are least precise for longest time durations. The other is external and arises from temporal variability of events in the outside world. The precision of temporal expectations thus decreases if events become more variable in time. It has long been recognized that the processing of time durations within the range of hundreds of milliseconds (interval timing) strongly depends on dopaminergic (DA) transmission. The role of DA for the precision of temporal preparation in humans, however, remains unclear. This study therefore directly assesses the role of DA in the precision of temporal preparation of motor responses in healthy humans. In a placebo-controlled double-blind design using a selective D2-receptor antagonist (sulpiride) and D1/D2 receptor antagonist (haloperidol), participants performed a variable foreperiod reaching task, under different conditions of internal and external temporal uncertainty. DA blockade produced a striking impairment in the ability of extracting temporal expectations across trials and on the precision of temporal representations within a trial. Large Weber fractions for interval timing, estimated by fitting subjective hazard functions, confirmed that this effect was driven by an increased uncertainty in the way participants were experiencing time. This provides novel evidence that DA regulates the precision with which we process time when preparing for an action.

The Victorians were still faster than us. Commentary: Factors influencing the latency of simple reaction time.

Woods et al. (2015) claim that secular Simple Reaction Time (SRT) slowing (Woodley et al., 2013), disappears once modern studies are corrected for software and hardware lag, and once Galton's data are corrected for fastest-response selection. Here, this is challenged with a reanalysis of the secular slowing of SRT in the UK amongst large (N > 500), population-representative age-matched (≊18–30 years) studies. Starting with Galton's sample, this is assigned the simulated value estimated by Dodonova and Dodonov (2013, who like Woods et al. were critical of secular SRT slowing, owing to measurement issues) on the basis that he collected the fastest of three trials (207.5 ms). The two sexes in Galton's study are combined (as in Woods et al.), raising the weighted sample mean to 208.5 ms. Next is the Wilkinson and Allison (1989) study, which attempted to replicate Galton's study one century later, collecting SRTs as part of an exhibit in the London Science Museum. An electronic chronoscope recorded SRTs on magnetic tape, and sampled over eight trials with micro-processor-determined variable foreperiods. The mean SRT value for the 1189 participants aged between 20 and 29 is 245 ms. The presence of long and variable foreperiods necessitates a penalty of 10 ms (Dodonova and Dodonov, 2013). Another 10 ms should be deducted based on key-pressing time (Dodonova and Dodonov, 2013), reducing the mean to 225 ms. The studies of Deary and Der (2005) and Der and Deary (2006) are also included. The first utilized the highly representative Scottish Twenty-07 cohort. Dodonova and Dodonov (2013) identified a 53 ms lag stemming from liquid crystal stimulus onset delay. This is subtracted from the weighted average of the two sexes (300.8 ms), along with another 10 ms for key-pressing time. The resultant mean is 237.8 ms. Dodonova and Dodonov (2013) cleaned the male data in the Der and Deary (2006) study, collected from the representative UK Health and Lifestyle Survey, by removing cases for which SRT standard deviations exceeded those for choice RT. This reduced the N from 834 to 661, and also reduced the mean from 300 to 284 ms. The estimate was also penalized for LCD onset delay and key-pressing time, reducing the mean to 221 ms. When the SRT value for the female sample is penalized equivalently the resulting value is 239 ms. In order to simulate the female N for the purposes of taking a weighted average of both sexes, the actual female N is reduced in proportion to the male N (79.3% = 881), yielding a weighted mean of 230.9 ms for a combined sample-size of 1472. Table ​Table11 presents the data used in the analysis. Table 1 SRT means, sample sizes and sampling years for four large, age-matched UK samples. Consistent with Dodonova and Dodonov (2013), N-weighted regression is employed, as the only data on sample variability is sample size. Figure ​Figure11 illustrates the secular trend in British SRT spanning 100 years. Figure 1 Secular SRT slowing across four large, representative studies from the UK spanning a century. Bubble-size is proportional to sample size. Combined N = 6622. The secular slowing between UK studies is statistically significant (β = 0.97; 95% CI = 0.969–0.971, N = 6622), at +22.8 ms a century. Additional evidence for generational SRT slowing comes from Verhaeghen (2014), who suggested that the ratio of longitudinal to cross-sectional age-related slowing might indicate generational changes in processing speed. Verhaeghen reports ratios for two SRT studies (0.91 and 1.15), implying both secular losses and gains. For the study of Deary and Der (2005), the SRT ratios are “censored because they were excessively large” (p. 256). In this study, the ratio of the cross-sectional slowing trend (taking the weighted average of all paired between-cohort differences rescaled in terms of change per decade for males and females), to the weighted average decadal longitudinal slowing trend for both the males and females is 0.73, for an N of 1926 (cf. Woodley et al., 2014, for a detailed reanalysis of this dataset utilizing curve-fitting). The weighted average of the three SRT “Verhaeghen ratios” is 0.9 (N = 4078)—tentatively consistent with generational declines (i.e., a ratio of < 1). In conclusion, Woods et al. (2015) have undoubtedly made an important contribution to the debate concerning the role of software and hardware lag in the inflation of contemporary estimates of SRT, however, the evidence for generational SRT slowing remains quite compelling.

Foreperiod and range effects on time interval categorization.

One factor influencing the perceived duration of a brief interval is the length of the period preceding it, namely the foreperiod (FP). When multiple FPs are varied randomly within a testing session, longer FPs result in longer perceived duration. The purpose of this study was to identify what characteristics modulate this effect. In a task where participants were asked to categorize the duration of target intervals with respect to a 100-ms standard, the FPs were distributed over a 150-, 300-, or 900-ms range with the midpoint (1000 ms) of these distributions being kept constant. The results indicate that the effect of the length of variable FPs on perceived duration was much stronger in the 900-ms range condition. More specifically, this effect is due to the differences between the shortest FPs. The results also reveal that, overall, there are more short responses in the 300-ms condition than in the other range conditions. Moreover, the data reveal that the narrower the distribution, the better the discrimination. One interpretation of the main result (range effect) is that a wider distribution leads to an increased prior uncertainty towards the foreperiod length.

Children can implicitly, but not voluntarily, direct attention in time.

Children are able to use spatial cues to orient their attention to discrete locations in space from around 4 years of age. In contrast, no research has yet investigated the ability of children to use informative cues to voluntarily predict when an event will occur in time. The spatial and temporal attention task was used to determine whether children were able to voluntarily orient their attention in time, as well as in space: symbolic spatial and temporal cues predicted where or when an imperative target would appear. Thirty typically developing children (average age 11 yrs) and 32 adults (average age 27 yrs) took part. Confirming previous findings, adults made use of both spatial and temporal cues to optimise behaviour, and were significantly slower to respond to invalidly cued targets in either space or time. Children were also significantly slowed by invalid spatial cues, demonstrating their use of spatial cues to guide expectations. In contrast, children’s responses were not slowed by invalid temporal cues, suggesting that they were not using the temporal cue to voluntarily orient attention through time. Children, as well as adults, did however demonstrate signs of more implicit forms of temporal expectation: RTs were faster for long versus short cue-target intervals (the variable foreperiod effect) and slower when the preceding trial’s cue-target interval was longer than that on the current trial (sequential effects). Overall, our results suggest that although children implicitly made use of the temporally predictive information carried by the length of the current and previous trial’s cue-target interval, they could not deliberately use symbolic temporal cues to speed responses. The developmental trajectory of the ability to voluntarily use symbolic temporal cues is therefore delayed, relative both to the use of symbolic (arrow) spatial cues, and to the use of implicit temporal information.

Task predictability influences the variable foreperiod effect: evidence of task-specific temporal preparation

Temporal preparation usually results in enhanced performance in choice reaction time tasks. The present study investigated to what extent temporal preparation involves increased readiness for task-specific processing requirements as opposed to increased task-independent readiness. Participants performed either a pitch, a letter, or a color discrimination task within a variable foreperiod paradigm and tasks alternated regularly between auditory and visual discriminations. In separate blocks of trials, the upcoming visual discrimination task was either predictable or unpredictable. We observed the standard variable foreperiod effect for both visual discrimination tasks irrespective of task predictability. Importantly, however, the variable foreperiod effect was larger when the visual discrimination task was predictable than when it was unpredictable. These results suggest that temporal preparation in choice reaction time tasks involves increased readiness for both task-independent and task-specific processing requirements.