Response-stimulus Interval Research Articles

The Variable Response-Stimulus Interval Effect and Sleep Deprivation: An Unexplored Aspect of Psychomotor Vigilance Task Performance

The Psychomotor Vigilance Task (PVT) contains variable response-stimulus intervals (RSI). Our goal is to investigate the effect of RSI on performance to determine whether sleep deprivation affects the ability to attend to events across seconds and whether this effect is independent of impairment in sustaining attention across minutes, as measured by time on task. A control group following their normal sleep routines and 3 groups exposed to 54 hours of total sleep deprivation performed a 10-minute PVT every 6 hours for 9 total test runs. Sleep deprivation occurred in a sleep laboratory with continuous behavioral monitoring; the control group took the PVT at home. Eighty-four healthy sleepers (68 sleep deprivation, 16 controls; 22 women; aged 18-35 years). Across groups, as the RSI increased from 2 to 10 seconds, mean RT was reduced by 69 milliseconds (main effect of RSI, P < 0.001). There was no interaction between the sleep deprivation and RSI effects. As expected, there was a significant interaction of sleep deprivation and time on task for mean RT (P = 0.002). Time on task and RSI effects were independent. Parallel analyses of percentage of lapses and percentage of false starts produced similar results. We demonstrate that the cognitive mechanism of attention responsible for response preparation across seconds is distinct from that for maintaining attention to task performance across minutes. Of these, only vigilance across minutes is degraded by sleep deprivation. Theories of sleep deprivation should consider how this pattern of spared and impaired aspects of attention may affect real-world performance.

The time course of task switching: A speed—accuracy trade-off analysis

On each trial of this study, participants either switched between or repeated two simple, two-choice tasks involving either letter or digit classifications. Speed-accuracy trade-off (SAT) curves were obtained using the response-signal method of eliciting speeded responses at various response time lags after the presentation of the stimulus for the second task. The key finding from separate analyses of the three SAT-curve parameters (intercept, rate, and asymptote) was that the location of the intercept of the SAT function (i.e., the point at which responding rises above chance) was shifted upward for both short and long response-stimulus intervals under task-switch conditions but only when the responses associated with each of the letter-digit stimulus components were incompatible.

Generic cognitive adaptations to task interference in task switching

The present study investigated how the activation of previous tasks interferes with the execution of future tasks as a result of temporal manipulations. Color and shape matching tasks were organized in runs of two trials each. The tasks were specified by a cue presented before a task run, cueing only the first trials of each run. Response times (RTs) and error rates were measured for task switching and task repetition conditions. Task interference was varied as a function of response-cue interval (RCI of 300 and 900 ms), that is, the interval between the task runs. Keeping the response–stimulus interval within the task runs constant at 300 ms allowed the disentangling of the direct effects of RCI manipulation on performance (first trials) from the general effects on performance (both trials in the run). The data showed similar performance improvement due to RCI increase on both trials in the task run. Furthermore, increasing RCI improved both switch and repetition performance to a similar extent. Together, our findings provide further evidence for accounts stressing generic effects of proactive task interference in task switching.

Negative priming (cognitive inhibition) in obsessive-compulsive disorder (OCD)

Cognitive disinhibition has been implicated in the pathogenesis of obsessive-compulsive disorder (OCD). Negative priming (NP) is regarded to tap into this function. While early studies indeed found reduced negative priming in OCD, attempts to replicate are both scarce and equivocal. Moreover, several studies in favor of the disinhibition hypothesis are plagued by methodological limitations. For the present investigation, 18 participants with OCD and 28 healthy controls underwent a computerized NP experiment with varying response-stimulus intervals. In addition, a variant of the paradigm with concurrent item presentation was employed to rule out the confounding impact of memory. Negative priming was comparable between groups yielding small between-group effect sizes. The present study challenges broad claims of disinhibition in OCD. In our view, the disinhibition account faces theoretical problems. Instead, theories implicating cognitive biases as well as metacognitive problems may more parsimoniously explain the idiosyncratic nature of OCD symptoms.

Speeding before and slowing after errors: Is it all just strategy?

People are usually faster before and slower after committing an error. This finding has traditionally been explained by strategic changes of response criteria to less or more conservative thresholds. This idea has been implemented in current cognitive control frameworks, where it is proposed that high or low levels of processing conflict can dynamically change these response thresholds to achieve optimal performance. However, recent evidence suggests that evaluation of conflict is time consuming and can potentially interfere with subsequent processing [Jentzsch, I., Dudschig, C., 2009. Why do we slow down after an error? Mechanisms underlying the effects of posterror slowing. Quarterly Journal of Experimental Psychology, 62, 209-218]. The present study aims to extend this finding by investigating whether similar mechanisms underlie effects of pre-error speeding and posterror slowing and whether the amplitude of the Ne/ERN predicts posterror slowing in the current task setting. The response stimulus interval (RSI) was systematically manipulated. Speed-up in pre-error trials was unaffected by RSI, suggesting that this effect is not the result of strategic, time-consuming control processes. Posterror slowing dramatically increased and performance became more error prone with decreasing RSI, providing further evidence for the idea that error evaluation can produce substantial interference with subsequent trial processing, particularly when there is insufficient time between the error and the subsequent event. Importantly, we did not find a positive relationship between the RSI-dependent change in posterror slowing and the Ne/ERN amplitude, questioning a direct link between the amplitude of this component and the amount of subsequent performance adjustments.

Knowing What to Respond in the Future Does Not Cancel the Influence of Past Events

Everyday tasks seldom involve isolate actions but sequences of them. We can see whether previous actions influence the current one by exploring the response time to controlled sequences of stimuli. Specifically, depending on the response-stimulus temporal interval (RSI), different mechanisms have been proposed to explain sequential effects in two-choice serial response tasks. Whereas an automatic facilitation mechanism is thought to produce a benefit for response repetitions at short RSIs, subjective expectancies are considered to replace the automatic facilitation at longer RSIs, producing a cost-benefit pattern: repetitions are faster after other repetitions but they are slower after alternations. However, there is not direct evidence showing the impact of subjective expectancies on sequential effects. By using a fixed sequence, the results of the reported experiment showed that the repetition effect was enhanced in participants who acquired complete knowledge of the order. Nevertheless, a similar cost-benefit pattern was observed in all participants and in all learning blocks. Therefore, results of the experiment suggest that sequential effects, including the cost-benefit pattern, are the consequence of automatic mechanisms which operate independently of (and simultaneously with) explicit knowledge of the sequence or other subjective expectancies.

Short Article: Why do we slow down after an error? Mechanisms underlying the effects of posterror slowing

People often become slower in their performance after committing an error, which is usually explained by strategic control adjustments towards a more conservative response threshold. The present study tested an alternative hypothesis for explaining posterror slowing in terms of behavioural interferences resulting from error monitoring by manipulating stimulus contrast and categorization difficulty in a choice reaction time task. The response-stimulus interval (RSI) was either short or long, using a between-subject (Experiment 1) and a within-subject design (Experiment 2). Posterror slowing was larger and posterror accuracy lower in short than in long RSI situations. Effects of stimulus contrast disappeared in posterror trials when RSI was short. At long RSIs, stimulus contrast was additive with posterror slowing. The results support the idea that at least two mechanisms contribute to posterror slowing: a capacity-limited error-monitoring process with the strongest influence at short RSIs and a criterion adjustment mechanism at longer RSIs.

Temporal characteristics of semantic perseverations induced by blocked-cyclic picture naming

When unimpaired participants name pictures quickly, they produce many perseverations that bear a semantic relation to the target, especially when the pictures are blocked by category. Evidence suggests that the temporal properties of these “semantic perseverations” may differ from typical lexical perseverations in aphasia. To explore this, we studied semantic perseverations generated by participants with aphasia on a naming task with semantic blocking [Schnur, T. T., Schwartz, M. F., Brecher, A., & Hodgson, C. (2006). Semantic interference during blocked-cyclic naming: Evidence from aphasia. Journal of Memory and Language, 54, 199–227]. The properties of these perseverations were investigated by analyzing how often they occurred at each lag (distance from prior occurrence) and how time (response-stimulus interval) influenced the lag function. Chance data sets were created by re-shuffling stimulus-response pairs in a manner that preserved unique features of the blocking design. We found that the semantic blocking manipulation did not eliminate the expected bias for short-lag perseverations (recency bias). However, immediate (lag 1) perseverations were not invariably the most frequent, which hints at a source of inconsistency within and across studies. Importantly, there was not a reliable difference between the lag functions for perseverations generated with a 5 s, compared to 1 s, response-stimulus interval. The combination of recency bias and insensitivity to elapsed time indicates that the perseveratory impetus in a named response does not passively decay with time but rather is diminished by interference from related trials. We offer an incremental learning account of these findings.

Reward rate optimization in two-alternative decision making: Empirical tests of theoretical predictions.

The drift-diffusion model (DDM) implements an optimal decision procedure for stationary, 2-alternative forced-choice tasks. The height of a decision threshold applied to accumulating information on each trial determines a speed-accuracy tradeoff (SAT) for the DDM, thereby accounting for a ubiquitous feature of human performance in speeded response tasks. However, little is known about how participants settle on particular tradeoffs. One possibility is that they select SATs that maximize a subjective rate of reward earned for performance. For the DDM, there exist unique, reward-rate-maximizing values for its threshold and starting point parameters in free-response tasks that reward correct responses (R. Bogacz, E. Brown, J. Moehlis, P. Holmes, & J. D. Cohen, 2006). These optimal values vary as a function of response-stimulus interval, prior stimulus probability, and relative reward magnitude for correct responses. We tested the resulting quantitative predictions regarding response time, accuracy, and response bias under these task manipulations and found that grouped data conformed well to the predictions of an optimally parameterized DDM.

Effects of Preparation Time and Foreknowledge on Task Switching

Recently,Task switching is an important paradigm for studying executive control.Switching cost refer to the performance differences in task-switch and task-repeat trials.Many issues and problems need further exploration.Theoretically,there is disagreement as to whether switch costs actually represents the task-set reconfiguration or the task-set inertia.Many studies have found that a prolonged preparation time reduces switch costs,which has been attributed to a task set reconfiguration process.However,unlike manipulations of preparation time,other studies have varied the predictability of task sequence and found that the preparation benefit was the same for switches and repetitions.The present study explored the interaction of preparation time and foreknowledge in task switching.In addition,in order to study the effects of preparation time predictability on the task switching,the preparation time(CSI) was manipulated by blocked or randomized within subjects. Two explicit task-cuing experiments were used with the same materials and procedure,preparation times of 150ms and 900ms,and foreknowledge of the full-and the partial-foreknowledge.The full-foreknowledge specified both task transition and task identity.The partial-foreknowledge specified only task transition information.The response-stimulus interval was constant at 800ms,to control the amount of repetition priming from the previous trial.To examine the effect of preparation time predictability on the preparation effects of switch costs,in experiment 1,the preparation time was blocked within subjects,and in experiment 2,the preparation time was randomized within subjects.The RT was measured as the main index. Repeated-measure ANOVA was performed for experiment 1 and 2.The results revealed that:(1) Under the conditions of preparation time predictability and unpredictability,the interaction between the preparation time and the foreknowledge was significant.Under the condition of predictability,the RT of repeat task and switch-to task trials decreased with increasing preparation time,but there are no significant differences in switch-to cost;the RT of switch-away task is affected by preparation time,and switch-away cost advanced with prolonging preparation time.Under the condition of unpredictability,the RT of three types of tasks reduced with rising preparation time,but both of switch-to and switch-away cost went up.(2) Compared to the switch-to task,the RT and switch cost of the switch-away task were longer.(3) Under of the two conditions,there is not the preparation effect.The experimental results suggest that the switch cost may represent the preparation of the new task set and a residual component,and the task switching was not effected by the predictability of the preparation time.

Locus of response slowing resulting from alternation‐based processing interference

In serial reaction time (RT) tasks, performance is strongly influenced by previous events. RT in Trial N is much slower after response changes than response repetitions from Trial N-2 to Trial N-1 when response-stimulus interval is short (I. Jentzsch & H. Leuthold, 2005). The aim of the present study was to investigate the mechanisms leading to this slowing by contrasting the idea of a hard bottleneck, postponing all subsequent processing, with a selective prolonging of postperceptual stages. We analyzed the lateralized readiness potential (LRP) and peak latencies of P1, N1, and P300 components in a choice RT task mapping four stimuli to two responses. Alternation-based interference affected the S-LRP interval but neither the LRP-R interval nor the latency of P1, N1, and P300. These findings suggest that, whereas alternation-based conflict originates at response-related stages, postconflict slowing selectively affects central, premotoric processing.

The effect of stimulus availability on task choice in voluntary task switching

The voluntary task switching paradigm allows subjects to choose which task to perform on each trial in a stimulus environment affording multiple tasks. The present study examined the effect of stimulus availability on task choice. Subjects viewed displays containing a digit and a letter and performed either an even/odd or a consonant/vowel judgment on each trial. The target stimuli appeared with a stimulus onset asynchrony (SOA) of 0, 50, 100, or 150 msec. The probability of performing the task associated with Stimulus 1 increased as SOA increased, indicating an effect of external or stimulus-driven factors on task choice. This effect of stimulus availability on task choice was greater when the response-stimulus interval was 400 msec than when it was 2,000 msec. This interaction of preparation interval and stimulus availability is explained within a model of task choice that includes both internal processes and external influences.

Investigating the role of conflict resolution in memory updating by means of the one-back choice RT task

The current study is inspired by recent findings, which suggest that conflict is involved in the updating of memory representations. It directly addresses the relation between memory updating and conflict resolution by means of the one-back choice reaction time (RT) task, an updating task, which requires participants to postpone their response to stimulus n until the subsequent stimulus n + 1 has been presented. In three experiments, a more detailed analysis of the one-back choice RT task is presented in order to further identify the role of conflict resolution in memory updating. The findings demonstrate that the one-back choice RT task, which allows motor preparation just like a simple RT task, is in fact performed slower than a simple RT task because it additionally involves conflict resolution. It is further shown that also the response-stimulus interval of the one-back task involves processes that affect the amount of conflict in the task. In the "General discussion", the theoretical relevance of these findings for the concept of updating is discussed.

A computational approach to negative priming

Priming is characterized by a sensitivity of reaction times to the sequence of stimuli in psychophysical experiments. The reduction of the reaction time observed in positive priming is well-known and experimentally understood (Scarborough et al., J. Exp. Psycholol: Hum. Percept. Perform., 3, pp. 1–17, 1977). Negative priming—the opposite effect—is experimentally less tangible (Fox, Psychonom. Bull. Rev., 2, pp. 145–173, 1995). The dependence on subtle parameter changes (such as response-stimulus interval) usually varies. The sensitivity of the negative priming effect bears great potential for applications in research in fields such as memory, selective attention, and ageing effects. We develop and analyse a computational realization, CISAM, of a recent psychological model for action decision making, the ISAM (Kabisch, PhD thesis, Friedrich-Schiller-Universität, 2003), which is sensitive to priming conditions. With the dynamical systems approach of the CISAM, we show that a single adaptive threshold mechanism is sufficient to explain both positive and negative priming effects. This is achieved by comparing results obtained by the computational modelling with experimental data from our laboratory. The implementation provides a rich base from which testable predictions can be derived, e.g. with respect to hitherto untested stimulus combinations (e.g. single-object trials).

Gradations of awareness in a modified sequence learning task

We argue performance in the serial reaction time (SRT) task is associated with gradations of awareness that provide examples of fringe consciousness [Mangan, B. (1993b). Taking phenomenology seriously: the “fringe” and its implications for cognitive research. Consciousness and Cognition, 2, 89–108, Mangan, B. (2003). The conscious “fringe”: Bringing William James up to date. In B. J. Baars, W. P. Banks & J. B. Newman (Eds.), Essential sources in the scientific study of consciousness (pp. 741–759). Cambridge, MA: The MIT Press.], and address limitations of the traditional SRT procedure, including criticism of exclusion generation tasks. Two experiments are conducted with a modified SRT procedure where irrelevant stimulus attributes obscure the sequence rule. Our modified paradigm, which includes a novel exclusion task, makes it easier to demonstrate a previously controversial influence of response stimulus interval (RSI) on awareness. It also allows identification of participants showing fringe consciousness rather than explicit sequence knowledge, as reflected by dissociations between different awareness measures. The NEO-PI-R variable Openness to Feelings influenced the diversity of subjective feelings reported during two awareness measures, but not the degree of learning and awareness as previously found with traditional SRT tasks [Norman, E., Price, M. C., & Duff, S. C. (2006). Fringe consciousness in sequence learning: the influence of individual differences. Consciousness and Cognition, 15(4), 723–760.]. This suggests possible distinctions between two components of fringe consciousness.

Effects of response–stimulus interval manipulation and articulatory suppression on task switching

We conducted three experiments using a list paradigm to examine how articulatory suppression and response–stimulus interval (RSI) manipulation affected task switching. Experiments 1 and 2 tested task-switching performance under a short and long RSI and three concurrent task conditions (control, articulatory suppression, and tapping) without external task cues. The results indicated that alternation had a greater effect under articulatory suppression than under the control and tapping conditions, and that articulatory suppression costs were unrelated to the RSI. In Experiment 3, an external task cue was provided with each stimulus, and the negative effect of articulatory suppression on alternation cost was eliminated. These results indicated that articulatory suppression effects did not differ between conditions of short and long RSI and that the availability of verbal representations of task information was independent of RSI length. This paper discussed the possible roles played by the phonological loop in task-switching paradigms.

The effect of task preparation in task switching as reflected on lateralized readiness potential

The present study examined whether task preparation had an equivalent beneficial effect for both switch and repeat trials in the context of a task switching paradigm. A pair-wise task-switching paradigm was used where each trial was comprised of two tasks that were either the same (task repeat) or different (task switch). The effect of preparation was manipulated so that participants either performed pure repeat trials or pure switch trials in separate blocks (foreknowledge conditions) or performed both switch and repeat trials within the same block (non-foreknowledge conditions). In addition, the time interval between the response to the first task and the onset of the next task's stimulus (response-stimulus interval, RSI) was set at either 300 ms or 600 ms. Both stimulus-locked and response-locked lateralized readiness potentials were measured to examine at what stage in time that task preparation affects the task performance. The results showed that task preparation had the same amount of beneficial effect on the stage of response selection for both switch and repeat trials, regardless of whether the RSI was short or long.

Switching between univalent task-sets in schizophrenia: ERP evidence of an anticipatory task-set reconfiguration deficit

Objective The present study used behavioral and event-related potential (ERP) indices of task-switching to examine whether schizophrenia patients have a specific deficit in anticipatory task-set reconfiguration. Methods Participants switched between univalent tasks in an alternating runs paradigms with blocked response-stimulus interval (RSI) manipulation (150, 300, 600, and 1200 ms). Nineteen high functioning people with schizophrenia were compared to controls that were matched for age, gender, education and premorbid IQ estimate. Results Schizophrenia patients had overall increased RT, but no increase in corrected RT switch cost. In the schizophrenia group, ERPs showed reduced activation of the differential positivity in anticipation of switch trial at the optimal 600 ms RSI and reduced activation of the frontal post-stimulus switch negativity at both 600 and 1200 ms RSI compared to the control group. Conclusions Despite no behavioral differences in task switching performance, anticipatory and stimulus-triggered ERP indices of task-switching suggest group differences in processing of switch and repeat trials, especially at longer RSI conditions that for control participants provide opportunity for anticipatory activation of task-set reconfiguration processes. Significance These results are compatible with impaired implementation of endogenously driven processes in schizophrenia and greater reliance on external task cues, especially at long preparation intervals.

Task reconfiguration and carryover in task switching: An event-related potential study

This study investigated the electrophysiological correlates of the processes involved in task switching. A pair-wise task-switching paradigm was used where each trial comprised two tasks that were either the same (task repeat) or different (task switch). In the paradigm, task-switch and repeat trials are compared in conditions of foreknowledge and non-foreknowledge of the forthcoming task type and during different response–stimulus intervals (RSIs). The results of this study show that, before the second task began in a task-pair trial, i.e., during the RSI, there was a CNV-like negativity for all trials. This indicates a general anticipatory effect. In foreknowledge conditions, there is an additional switch-specific reconfiguration process followed by a task-specific (including both switch- and repeat-related) preparatory process. During the post-task 2 stage, P3b was found to be smaller in switch trials than in repeat trials. Such differential P3b between switch and repeat trials appeared earlier and larger in foreknowledge than in non-foreknowledge conditions. The results of this study support the existence of advance preparation and uphold the role of carryover effects in task switching.

Cue-based preparation and stimulus-based priming of tasks in task switching

In this study, we investigated the interaction of three different sources of task activation in precued task switching. We distinguished (1) intentional, cue-based task activation from two other, involuntary sources of activation: (2) persisting activation from the preceding task and (3) stimulus-based task activation elicited by the task stimulus itself. We assumed that cue-based task activation increases as a function of cue-stimulus interval (CSI) and that task activation from the preceding trial decays as a function of response-stimulus interval Stimulus-based task activation is thought to be due to involuntary retrieval of stimulus-associated tasks. We manipulated stimulus-based task activation by mapping each of the stimuli consistently to only one or the other of the two tasks. After practice, we reversed this mapping in order to test the effects of item-specific stimulus-task association. The mapping reversal resulted in increased reaction times and increased task shift costs. These stimulus-based priming effects were markedly reduced with a long CSI, relative to a short CSI, suggesting that stimulus-based priming shows up in performance principally when competition between tasks is high and that cue-based task activation reduces task competition. In contrast, lengthening the response-cue interval (decay time) reduced shift costs but did not reduce the stimulus-based priming effect The data are consistent with separable stimulus-related and response-related components of task activation. Further theoretical implications of these findings are discussed.