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.

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.

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.

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.

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.

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.

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.

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.

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).

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).

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.

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.

Representations of temporal information in short-term memory: Are they modality-specific?

Rattat and Picard (2012) reported that the coding of temporal information in short-term memory is modality-specific, that is, temporal information received via the visual (auditory) modality is stored as a visual (auditory) code. This conclusion was supported by modality-specific interference effects on visual and auditory duration discrimination, which were induced by secondary tasks (visual tracking or articulatory suppression), presented during a retention interval. The present study assessed the stability of these modality-specific interference effects. Our study did not replicate the selective interference pattern but rather indicated that articulatory suppression not only impairs short-term memory for auditory but also for visual durations. This result pattern supports a crossmodal or an abstract view of temporal encoding.

Temporal discrimination of one's own reaction times in dual-task performance: Context effects and methodological constraints.

In this study we used the method of constant stimuli to investigate introspective reaction times in the psychological refractory period (PRP) paradigm under different temporal contexts. Previous introspective PRP studies have mostly used visual analogue scales to assess introspective reaction times and found that participants were largely unaware of the typical dual-task costs that arise in this paradigm (PRP effect). This apparent limitation of introspection has been taken as evidence for a serial processing bottleneck that encompasses response selection as well as conscious perception. In our study, in each trial participants first performed the PRP task and were then presented with a comparison interval that they had to compare with their reaction time to the second task (RT2). Across three experiments, we observed that the subjective estimates of RT2 (i.e., the points of subjective equality) did not reflect the objective pattern but were almost completely biased toward the center of the comparison intervals (asymmetry effect). In a control experiment in which participants discriminated RT2s of other participants without performing the PRP task, this bias was largely reduced. We interpret these results as indicating that in dual-task performance participants acquire only poor temporal representations of their own reaction times, and the apparent unawareness of the PRP effect may reflect disturbed timing abilities rather than a conscious perception bottleneck.

Multiple timing of nested intervals: Further evidence for a weighted sum of segments account.

How people perceive temporally overlapping intervals can inform us about the architecture and constraints of the human timing system. In the present study, we examined the time perception of two overlapping intervals in a nested context. In this context, one short interval (1 s) was temporally nested within another long interval (3 s). The data showed that although participants' perception of the short interval was unaffected by its temporal position within the long interval, estimates of the long interval decreased, the later the short interval appeared. These data indicate that participants perceive two overlapping intervals as three segments that must be summed in order to estimate the long interval. Importantly, the temporal relationships between overlapping intervals affect the estimates, because a recency weighting is applied to each segment during the summing process. Within pacemaker-accumulator models, these results could be seen as supporting a timing system composed of a single pacemaker and a single accumulator, but they could also constrain any account of human interval timing.

Does semantic redundancy gain result from multiple semantic priming?

Fiedler, Schröter, and Ulrich (2013) reported faster responses to a single written word when the semantic content of this word (e.g., "elephant") matched both targets (e.g., "animal", "gray") as compared to a single target (e.g., "animal", "brown"). This semantic redundancy gain was explained by statistical facilitation due to a race of independent memory retrieval processes. The present experiment addresses one alternative explanation, namely that semantic redundancy gain results from multiple pre-activation of words that match both targets. In different blocks of trials, participants performed a redundant-targets task and a lexical decision task. The targets of the redundant-targets task served as primes in the lexical decision task. Replicating the findings of Fiedler et al., a semantic redundancy gain was observed in the redundant-targets task. Crucially, however, there was no evidence of a multiple semantic priming effect in the lexical decision task. This result suggests that semantic redundancy gain cannot be explained by multiple pre-activation of words that match both targets.

How are overlapping time intervals perceived? Evidence for a weighted sum of segments model.

This study investigated the way in which people time two overlapping intervals. Timing models already proposed in the literature predict different effects of the degree of overlap on each estimate, and empirical findings were compared to these predictions. Two unimodal experiments (in which each to-be-timed interval was a visual stimulus) and one bimodal experiment (in which one to-be-timed interval was auditory and the other visual) were conducted. The estimate of the first interval was either unaffected or decreased, and the estimate of the second interval consistently increased as the intervals were more temporally separated. The only model in the literature that could account for such result patterns is a single pacemaker single accumulator structure with an additional recency weighting (see the weighted sum of segments model). That is, participants appear to segment the two overlapping intervals into three non-overlapping and overlapping segments, time these segments separately, and then combine them to estimate each interval. Importantly, a recency weighting, determined by the time that has passed since the end of that segment, is also applied to each segment in the summation process. Further, in the bimodal experiment the order in which the stimuli of different modalities were presented affected the way in which they were timed, a finding that none of the current models can explain. This highlights that a comprehensive model of interval timing must consider not only the modalities of to-be-timed intervals but also the order in which different modalities must be timed.

Are introspective reaction times affected by the method of time estimation? A comparison of visual analogue scales and reproduction.

In this study, we investigated whether the method of time estimation plays a role in the apparent limits of introspection in dual-task processing. Previous studies showed that when participants reported introspective reaction times after each trial of a dual task by clicking on a visual analogue scale, they appeared to be unaware of the dual-task costs in their performance. However, visual analogue scales have seldom been used in interval estimation, and they may be inappropriate. In the present study, after each dual-task trial, participants reported their introspective reaction times either via a visual analogue scale or via the method of reproduction. The results replicated the previous findings, irrespective of method. That is, even though responses to the second task slowed down with increasing task overlap, this slowing was only very weakly reflected in the introspective reaction times. Thus, the participants' failure to report the objective dual-task costs in their reaction times is a rather robust finding that cannot be attributed to the method employed. However, introspective reaction times reported via visual analogue scales were more closely related to the objective reaction times, suggesting that visual analogue scales are preferable to reproduction. We conclude that introspective reaction times represent the same information regardless of method, but whether that information is temporal in nature is as yet unsettled.