How does it feel? Passage of time judgments in speeded RT performance.

The relationship between duration perception and the feeling of time passing (passage of time) is not yet understood. In the present study, we assessed introspective reaction times (RT) and passage of time judgments in a speeded RT task. Task difficulty was manipulated in a numerical comparison task by numerical distance (distance from the number 45) and notation (digit vs. word). The results showed that both effects were reflected in introspective RTs, replicating previous results. Moreover, passage of time judgments showed a very similar pattern, with slower passage of time for more difficult comparisons. These results suggest that in the millisecond range judgments of duration and passage of time largely mirror each other when participants introspect about their own RT performance.

Subjective estimates of total processing time in dual-tasking: (some) good news for bad introspection.

Previous studies have shown severe distortions of introspection about dual-task interference in the Psychological Refractory Period (PRP) paradigm. The present study investigated participants' ability to introspect about the total trial time in this paradigm, as this temporal information may arguably be more relevant for strategic task scheduling than subjective estimates of each task within the dual task. To this end, participants provided estimates of their reaction times (IRTs) for the two subtasks in one half of the experiment, and estimates of the total trial time (ITTs) in the other half of the experiment. Although the IRT results showed the typical unawareness of the PRP effect, ITTs reflected the effects of SOA and Task 2 difficulty on objective total trial time. Additional analyses showed that IRTs were influenced by the introspective task order; that is, the ITT pattern carried over to IRTs when IRTs were assessed in the second half of the experiment. Overall, the present results show that people are able to accurately introspect about total trial time in the PRP paradigm and thus provide some good news for bad introspection in the PRP paradigm.

The surprising role of stimulus modality in the dual-task introspective blind spot: a memory account.

Being able to accumulate accurate information about one's own performance is important in everyday contexts, and arguably particularly so in complex multitasking contexts. Thus, the observation of a glaring gap in participants' introspection regarding their own reaction time costs in a concurrent dual-task context is deserving of closer examination. This so-called introspective blind spot has been explained by a 'consciousness bottleneck' which states that while attention is occupied by one task, participants cannot consciously perceive another stimulus presented in that time. In the current study, a series of introspective Psychological Refractory Period (PRP) experiments were conducted to identify the determinants of an introspective blind spot; to our surprise, in half of the experiments participants appeared to be aware of their dual-task costs. A single trial analysis highlighted the sensory modality of the two stimuli within the trial as an important predictor of introspective accuracy, along with temporal gaps in the trial. The current findings call into question the claim that attention is required for conscious awareness. We propose a memory-based account of introspective processes in this context, whereby introspective accuracy is determined by the memory systems involved in encoding and rehearsing memory traces. This model of the conditions required to build up accurate representations of our performance may have far-reaching consequences for monitoring and introspection across a range of tasks.

Introspection about backward crosstalk in dual-task performance.

The present study investigated participants' ability to introspect about the effect of between-task crosstalk in dual tasks. In two experiments, participants performed a compatibility-based backward crosstalk dual task, and additionally provided estimates of their RTs (introspective reaction times, IRTs) after each trial (Experiment 1) or after each pair of prime and test trials (Experiment 2). In both experiments, the objective performance showed the typical backward crosstalk effect and its sequential modulation depending on compatibility in the previous trial. Very similar patterns were observed in IRTs, despite the typical unawareness of the PRP effect. In sum, these results demonstrate the reliability of between-task crosstalk in dual tasks and that people's introspection about the temporal processing demands in this complex dual-task situation is intriguingly accurate and severely limited at the same time.

Short-term memory of temporal information revisited.

Previous studies provided diverging evidence regarding modality specificity of temporal information in short-term memory. Some authors reported modality-specific interference effects on visual and auditory duration discrimination, whereas others observed crossmodal interference effects. One reason for these diverging results could be different trade-offs between the temporal discrimination task and the interference task in these studies. Therefore, this study re-examined these effects with interference tasks (speeded color/pitch change discrimination) that were especially suited to assess potential trade-offs between the primary and the secondary tasks. The results showed that the auditory interference task selectively impaired discrimination performance for auditory durations, whereas the visual interference task proved to be inefficient as interference task. The present results agree best with an account that suggests a modality-specific representation of temporal information in short-term memory.

Temporal sequence discrimination within and across senses: do we really hear what we see?

Previous evidence suggests that people "hear" visual stimuli when encoding temporal information. This suggestion is based on the observation that auditory distractor information can strongly affect discrimination performance for visual temporal sequences. The present study aimed to replicate and extend this finding by investigating sequence discrimination within and across the two modalities. In two experimental series, participants judged whether two subsequently presented temporal sequences, a standard sequence followed by a comparison sequence, were identical or not. In Experimental Series A, irrelevant distractor information was presented simultaneously with the standard sequence. In Series B, the distraction appeared in the retention interval between the standard sequence and the comparison sequence. The results showed that auditory distraction impaired performance irrespective of whether the target sequences were auditory or visual, whereas visual distraction only impaired the discrimination of visual target sequences. Furthermore, auditory distraction was always at least as effective as visual distraction, irrespective of standard modality. Generally, discrimination performance was much better for auditory than for visual sequences. Overall, the present results are consistent with the idea that people code visual temporal information in the auditory modality. Moreover, the present study also suggests that such cross-modal interference effects should be interpreted cautiously with respect to their underlying timing mechanism because of the basic differences in temporal sensitivity between the two modalities.

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.

Introspective reports of reaction times in dual-tasks reflect experienced difficulty rather than timing of cognitive processes.

Reports of introspective reaction times (iRTs) have been used to investigate conscious awareness during dual-task situations. Previous studies showed that dual-task costs in RTs (the psychological refractory period, PRP, effect) are not reflected in participants' introspective reports. This finding has been attributed to conscious awareness of Task 2 being delayed while Task 1 is centrally processed. Here, we test this Temporal model and compare it to an alternative that assumes participants base their iRTs on experienced difficulty. We collected iRTs and difficulty estimates after each trial of a PRP paradigm in which the perceptual difficulty of either Task 2 (Experiment 1) or Task 1 (Experiment 2) was manipulated. Our results largely support the difficulty-based account, suggesting that in a dual-task situation, iRTs do not reflect timing of cognitive processes but are strongly influenced by the experience of difficulty.

Distorted subjective reports of stimulus onsets under dual-task conditions: Delayed conscious perception or estimation bias?

We investigated whether selecting a response for one task delays the conscious perception of another stimulus (delayed conscious perception hypothesis). In two experiments, participants watched a revolving clock hand while performing two tasks in close succession (i.e. a dual-task). Two stimuli were presented with varying stimulus onset asynchrony (SOA). After each trial, participants separately estimated the onsets of the two stimuli on the clock face. Across two experiments and four conditions, we manipulated response requirements and assessed their impact on perceived stimulus onsets. Results showed that (a) providing speeded responses to the stimuli did lead to greater SOA-dependent misperceptions of both stimulus onsets as compared to a solely perceptual condition, and (b) that response grouping reduced these misperceptions. Overall, the results provide equivocal evidence for the delayed conscious perception hypothesis. They rather suggest that participants' estimates of the two stimulus onsets are biased by the interval between their responses.

Ebbinghaus, Müller-Lyer, and Ponzo: Three examples of bidirectional space-time interference.

Previous studies have shown interference between illusory size and perceived duration. The present study replicated this space-time interference in three classic visual-spatial illusions, the Ebbinghaus, the Müller-Lyer, and the Ponzo illusion. The results showed bidirectional interference between illusory size and duration for all three illusions. That is, subjectively larger stimuli were judged to be presented longer, and stimuli that were presented longer were judged to be larger. Thus, cross-dimensional interference between illusory size and duration appears to be a robust phenomenon and to generalize across a wide range of visual size illusions. This space-time interference most likely arises at the memory level and supports the theoretical notion of a common representational metric for space and time.

Time and visual-spatial illusions: Evidence for cross-dimensional interference between duration and illusory size.

Time and space are intimately related to each other. Previous evidence has shown that stimulus size can affect perceived duration even when size differences are illusory. In the present study, we investigated the effect of visual-spatial illusions on duration judgments in a temporal reproduction paradigm. Specifically, we induced the Ebbinghaus illusion (Exp. 1) and the horizontal-vertical illusion (Exp. 2) during the encoding phase of the target interval or the reproduction phase. The results showed (a) that illusory size affects temporal processing similarly to the way physical size does, (b) that the effect is independent of whether the illusion appeared during encoding or reproduction, and (c) that the interference between size and temporal processing is bidirectional. These results suggest a rather late locus of size-time interference in the processing stream.

Perceptual learning in temporal discrimination: asymmetric cross-modal transfer from audition to vision.

This study assessed possible cross-modal transfer effects of training in a temporal discrimination task from vision to audition as well as from audition to vision. We employed a pretest-training-post-test design including a control group that performed only the pretest and the post-test. Trained participants showed better discrimination performance with their trained interval than the control group. This training effect transferred to the other modality only for those participants who had been trained with auditory stimuli. The present study thus demonstrates for the first time that training on temporal discrimination within the auditory modality can transfer to the visual modality but not vice versa. This finding represents a novel illustration of auditory dominance in temporal processing and is consistent with the notion that time is primarily encoded in the auditory system.

Time-course analysis of temporal preparation on central processes.

Participants usually respond faster to a response signal (RS) when this signal is preceded by a warning stimulus than when it is not. A question of theoretical importance is the locus of this facilitating effect within the information processing stream. Recently, Los and Schut (Cogn Psychol 57:20-55, 2008) suggested that temporal preparation acts on central processes while perception of the RS is under way. The present study provides a stochastic model (central preparation model, CPM) based on this hypothesis and presents three experiments testing this model. To track the complete time-course of temporal preparation, the warning signal could either precede or follow the RS. The data show some systematic deviation from the model's predictions, questioning CPM's assumption that temporal preparation acts only on central processes. An alternative mechanism of temporal preparation based on the parallel grains model [Miller and Ulrich (Cogn Psychol 46:101-151, 2003)] is discussed.

Timing of internal processes: Investigating introspection about the costs of task switching and memory search.

During the last two decades, there has been new interest in introspection about multitasking performance. In this field, subjective timing of one's own reaction times (introspective RTs) has proven a useful measure to assess introspection. However, whether timing our own cognitive processing makes use of the same timing mechanisms as timing external intervals has been called into question. Here we take a novel approach to this question and build on the previously observed dissociation between the interference of task switching and memory search with a concurrent time production task whereby temporal productions increased with increasing memory set size but were not affected by switch costs. We tested whether a similar dissociation could be observed in this paradigm when participants provide introspective RTs instead of concurrent temporal productions. The results showed no such dissociation as switch costs and the effect of memory set size on RTs were both reflected in introspective RTs. These findings indicate that the underlying timing mechanisms differ between temporal productions and introspective RTs in this multitasking context, and that introspective RTs are still strikingly accurate estimates of objective RTs.

S1-R2 and R1-R2 Backward Crosstalk Both Affect the Central Processing Stage.

A frequent observation in dual-task experiments is that performance in Task 1 is influenced by conceptual or spatial overlap with features of Task 2. Such compatibility-based backward crosstalk effects (BCEs) can occur when overlap exists between the responses of two tasks-the R1-R2 BCE-or between the stimulus in Task 1 and the response in Task 2-the S1-R2 BCE. The present study investigated whether the S1-R2 BCE has a perceptual locus, and by implication, whether the two BCEs have a common processing locus or different ones. To this end, we applied the additive factors logic and manipulated the duration of the Task 1 perceptual stage. The results argue against a perceptual locus for both BCEs. As a possible explanation, we suggest that the R1-R2 BCE and the S1-R2 BCE have their locus within a capacity-limited central stage, but that they arise from different processes within this stage. The R1-R2 BCE influences Task 1 response selection, whereas the S1-R2 BCE influences Task 1 stimulus classification. A plausible though post-hoc model is presented within the Discussion.

The effect of 40 h constant wakefulness on task-switching efficiency.

This study investigated efficiency of switching between different tasks in 12 male participants (19-30 years) during 40 h of constant wakefulness. As index of task-switching efficiency, switch costs in reaction time were assessed every 3 h under controlled behavioural and environmental conditions. Overall reaction times and switch costs showed a temporal pattern consistent with the assumption of a combined influence of a sleep homeostatic and a circadian process. An additional analysis indicated that the variation in switch costs could not be attributed to interference of the current task with persisting activation from preceding tasks. We therefore conclude that sleep loss and the circadian system affect the ability to prepare the current task rather than automatic processing of irrelevant stimulus information.

Introspection is not always blind to the costs of multitasking: The case of task switching.

Previous studies have provided evidence that introspection about dual-task performance in the psychological refractory period (PRP) paradigm is severely limited. The present study investigated introspection at the other pole of the multitasking continuum, namely task switching. In 2 experiments, participants provided estimates of their response times (i.e., introspective RTs) after each trial in modified versions of the alternating-runs and the task-cuing paradigm, which included only 2 tasks in a trial. In contrast to the previously observed unawareness of dual-task costs in the PRP paradigm, participants reported their switch costs in introspective RTs. Thus, introspection about multitasking performance appears to not always be as limited as in the PRP paradigm. Nevertheless, introspection is not without limits also in task switching. Participants only partly reported the beneficial impact of longer preparation time on their performance. The present results suggest that introspective RTs depend on multiple cues, of which some are valid and some are invalid. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Temporal reproduction within and across senses: Testing the supramodal property of the pacemaker-counter model.

The human ability to compare time between sensory modalities implies a supramodal representation of time. This notion is consistent with the pacemaker-counter model (PCM), the core architecture of prominent timing theories. Some theorists, however, have promoted modality-specific timing mechanisms, which might hamper crossmodal temporal comparison. This study tested whether PCM is sufficient to account for intra- as well as crossmodal timing. To account for modality-specific timing differences, we proceeded from the common assumption that the pacemaker runs faster for auditory than for visual stimuli. Participants reproduced short and long standards (800 vs. 2,400 ms) by terminating a comparison stimulus. In Experiment 1, in each trial the sensory modalities (auditory vs. visual) of the standard and the comparison were the same (congruent) or different (incongruent). PCM implies that timing performance depends on modality order. However, there should be virtually no congruency effects on overall performance. Although the results largely matched the predictions of PCM, there were substantial congruency effects on reproduction variability especially in the subsecond range. Three intramodal control experiments, however, showed that similar congruency effects can be observed when the standard and the comparison differ in intramodal characteristics. This suggests that temporal representations are not isolated from nontemporal stimulus characteristics, even when these are subtle and within the same modality. The present results can be interpreted as evidence for sensory timing within the subsecond range. Nevertheless, we used computer simulations to evaluate extensions of PCM that could account for the present result pattern, while retaining PCM's supramodal property. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Are participants' reports of their own reaction times reliable? Re-examining introspective limitations in active and passive dual-task paradigms.

There is a known introspective limitation in the Psychological Refractory Period (PRP) paradigm - people underestimate the dual-task costs on their second reaction time. The prevailing explanation for this is that conscious awareness of the second stimulus is delayed in time until the first task has been centrally processed. Here, we examined this effect in more detail, by comparing reaction time estimates after processing a PRP task, and after passively experiencing 'replays' of PRP trials. Even when participants had no dual-task processing demands, they did not accurately report the reaction time intervals using a visual analogue scale (the original reporting method of most introspective PRP experiments), but they did when placing markers that represent each event on a timeline. Thus, the timeline seems to better represent participants' introspective representation of the trial. Importantly, introspection limitations still existed when participants processed the PRP task and then recreated it on a timeline.

Filled and empty motor reproductions of filled and empty intervals: Is there also a filled - reproduction illusion?

Previous studies have demonstrated that filled intervals are perceived as being longer than empty intervals of the same duration (i.e., the filled - duration illusion). In the present study, we asked whether the motor actions involved in filled and empty reproductions (a single continuous key press vs. two discrete key presses) would affect time estimates in a similar way. We hypothesized that reproductions of intervals of the same duration should be shorter for filled than empty reproductions (i.e., a filled - reproduction illusion). In two experiments, participants reproduced filled and empty intervals (ranging from 400 to 1,600 ms) using filled and empty reproductions. The results provided evidence for both kinds of illusions, even though the evidence was clearer for the filled - duration than for the filled - reproduction illusion. The present study demonstrates that in a situation in which both illusions work in concert, reproductions of the same interval can vary dramatically depending on the combination of interval and reproduction type.