Boosting working memory with accelerated clocks.

Our perception of time varies with the degree of cognitive engagement in tasks. The perceived passage of time accelerates while working on demanding tasks, whereas time appears to drag during boring situations. Our experiment aimed at investigating whether this relationship is mutual: Can manipulated announcements of elapsed time systematically affect the attentional resources applied to a cognitive task? We measured behavioral performance and the EEG in a whole report working memory paradigm with six items of different colors that each had to be reported after a short delay period. The 32 participants were informed about the current time after each 20 trials, while the clock was running at either 100% (normal), 120% (fast), or 80% (slow) of normal clock speed depending on the experimental block. The mean number of correctly reported colors per trial was significantly increased in the fast as compared to the slow and normal clock conditions. In the EEG, we focused on neural oscillations during working memory encoding and storage. As an electrophysiological correlate of task engagement, frontal theta power during the storage interval was increased in the fast clock condition. Also, the power of frontal theta oscillations predicted the number of correctly reported colors on a single-trial basis. This shows that a covert manipulation of clock speed can lead to an improvement in cognitive performance, presumably mediated by a higher allocation of attentional resources resulting from an adaptation of the subjective passage of time during an experiment.

Stroop task performance across the lifespan: High cognitive reserve in older age is associated with enhanced proactive and reactive interference control.

Susceptibility to interference increases with age but there is large inter-individual variability in interference control in older adults due to a number of biological and environmental factors. The present study aims at analyzing behavior and ERPs in a Stroop interference task with increasing difficulty in a sample of 246 young, middle-aged and healthy old participants. The old age group was divided into three subgroups based on performance scores. The results show a gradual performance reduction with increasing age and task difficulty. However, old high performers reached a performance level comparable to middle-aged subjects. The contingent negative variation (CNV) reflecting preparation and proactive task control and the target-locked P2/N2 complex associated with retrieval and implementation of S-R mappings during reactive task control were larger in the old high than low performers and similar to middle-aged or even young participants. High performance was limited to executive control tasks, while other cognitive functions were less affected. In addition, high performance was associated with higher level of education, usage of foreign languages and higher IQ. Thus, the performance differences in old age were discussed in the framework of cognitive reserve that constitutes individual differences in neural networks underlying task performance.

Quantifying the Wollaston Illusion.

In the early 19th century, William H. Wollaston impressed the Royal Society of London with engravings of portraits. He manipulated facial features, such as the nose, and thereby dramatically changed the perceived gaze direction, although the eye region with iris and eye socket had remained unaltered. This Wollaston illusion has been replicated numerous times but never with the original stimuli. We took the eyes (pupil and iris) from Wollaston's most prominent engraving and measured their perceived gaze direction in an analog fashion. We then systematically added facial features (eye socket, eyebrows, nose, skull, and hair). These features had the power to divert perceived gaze direction by up to 20°, which confirms Wollaston's phenomenal observation. The effect can be thought of as an attractor effect, that is, cues that indicate a slight change in head orientation have the power to divert perceived gaze direction.

A standard conceptual framework for the study of subjective time.

Research on the mental representation of time ('subjective time') has provided broad insights into the nature of time perception and temporal processing. As the field comprises different scientific disciplines, such as psychology, philosophy, and neuroscience, studies differ with regard to the basic terms and concepts used. For this reason, research on subjective time lacks a coherent conceptual system. We argue that research in the field of subjective time should aim at establishing such a system, i.e., a more standardized terminology, in order to strengthen its theoretical basis and to support an efficient communication of results. Based on key empirical findings and concepts that are commonly (but inconsistently) used in the literature, we argue for a conceptual framework for the study of subjective time that differentiates between three types of mental representations of time: basic temporal processing, time perception in terms of passage, and time perception in terms of duration.

Cognitions about time affect perception, behavior, and physiology - A review on effects of external clock-speed manipulations.

Our understanding of (altered) time perception may benefit from investigating its potential effects upon other psychological and physiological parameters. To date, however, only a few rather isolated studies have experimentally manipulated the subjective passage of time or the amount of apparently elapsed duration in order to investigate such effects. Based on our review of these studies, first, altered time perception can be induced effectively by means of rigged (accelerated or decelerated) external clocks, second, these clock-speed manipulations remain unnoticed by most participants, and third, several psychological, cognitive, behavioral, and physiological variables can be affected, e.g., fatigue, hunger, pain perception. However, the existing studies on time-perception manipulation do not systematically relate to each other and the underlying mechanisms of the observed effects are poorly understood. Based on cognitive appraisal theories and the given empirical results, we propose a cognitive framework for interpreting and explaining the effects of manipulations of time perception.

Is mental time embodied interpersonally?

Recent evidence has shown that the mental representation of time is "embodied"-time is expressed via the hands, the eyes, and the whole body. These findings suggest the existence of a manually reflected mental time line running (in Western culture) horizontally from left (past) to right (future) and an ocularly reflected mental time line running from left/down (past) to right/up (future). We addressed the question whether mental time is also reflected interpersonally and investigated whether an avatar's face orientation (left vs. right) would facilitate a subject's temporal processing in relation to the horizontal mental time line. In combination with a left- or right-gazing avatar, we presented a temporal auditory word ("gestern"-yesterday or "morgen"-tomorrow), and our subjects had to manually categorize the word as being either past- or future-related (classic left/right key-press paradigm). The stimulus-response (SR) mapping was either compatible (past word-left hand, future word-right hand) or incompatible (future word-left hand, past word-right hand). Responses were significantly faster in blocks with compatible versus incompatible mapping. Thus, our results provide clear evidence for manually reflected mental time running from left to right, even for temporal auditory words that are free of potential visual (reading direction) confounds. The presented interpersonal cues (avatar head orientation) facilitated the activation of the horizontal mental time line in blocks with incompatible SR-mapping but not in blocks with compatible (standard) mapping. We conclude that interpersonal cues exert weak effects on the spatial representation of mental time and can help to adapt context-specific mappings of temporal concepts.

How Long Did You Look At Me? The Influence of Gaze Direction on Perceived Duration and Temporal Sensitivity.

Faces that exhibit emotionally negative expressions in mutual gaze have been shown to induce a dilation of perceived duration. The influence of gaze by itself on duration judgments, however, has rarely been investigated. We argue for a social interaction hypothesis, according to which humans should be highly accurate and precise (sensitive) when processing the temporal dynamics of mutual gaze. In three experiments, we investigated whether the direction of observed gaze affects perceived duration and temporal sensitivity. In Experiment 1, subjects did indeed estimate the duration of direct gaze more accurately as compared to the duration of averted gaze. In Experiments 2 and 3, subjects had to categorize direct and averted gaze stimuli as being short or long in duration (temporal bisection). Experiment 2 found temporal sensitivity (but not mean duration judgments) to be improved in cases of mutual gaze. In Experiment 3, the effect of mutual gaze on prolonged subjective duration did replicate, however, it was rather small. Moreover, temporal precision was not improved in the case of naturalistic stimuli. In sum, effects of mutual gaze on duration judgments are rather weak, and cannot be attributed to arousal, as such ratings did not differ between direct and averted gaze stimuli.

Adapting to the pandemic: longitudinal effects of social restrictions on time perception and boredom during the Covid-19 pandemic in Germany.

With the Covid-19 pandemic, many governments introduced nationwide lockdowns that disrupted people's daily routines and promoted social isolation. We applied a longitudinal online survey to investigate the mid-term effects of the mandated restrictions on the perceived passage of time (PPT) and boredom during and after a strict lockdown in Germany. One week after the beginning of the lockdown in March 2020, respondents reported a slower PPT and increased boredom compared to the pre-pandemic level. However, in the course of the lockdown, PPT accelerated and boredom decreased again until August 2020. Then, in October 2020, when incidence rates sharply rose and new restrictions were introduced, we again observed a slight trend toward a slowing of PPT and an increase of boredom. Our data also show that as the pandemic progressed, respondents adjusted their predictions about the pandemic's duration substantially upward. In sum, our findings suggest that respondents adapted to the pandemic situation and anticipated it as the new "normal". Furthermore, we determined perceived boredom and the general emotional state to be predictive of PPT, while depressive symptoms played a minor role.

Physical distancing and the perception of interpersonal distance in the COVID-19 crisis.

In the wake of the COVID-19 pandemic, it has been mandated to keep enlarged distances from others. We interviewed 136 German subjects over five weeks from the end of March to the end of April 2020 during the first wave of infections about their preferred interpersonal distance (IPD) before, during, and after the COVID-19 pandemic. In response to the pandemic, subjects adapted to distance requirements and preferred a larger IPD. This enlarged IPD was judged to partially persist after the pandemic crisis. People anticipated keeping more IPD to others even if there was no longer any risk of a SARS-CoV-2 infection. We also sampled two follow-up measurements, one in August, after the first wave of infections had been flattened, and one in October 2020, at the beginning of the second wave. Here, we observed that IPD varied with the incidence of SARS-CoV-2 within Germany. Overall, our data indicated that adaptation to distance requirements might happen asymmetrically. Preferred IPD rapidly adapted in response to distance requirements, but an enlargement of IPD may partially linger after the COVID-19 pandemic-crisis. We discuss our findings in light of proxemic theory and as an indicator for socio-cultural adaptation beyond the course of the pandemic.

Don't stop me now: Hampered retrieval of action plans following interruptions.

How can we retrieve action plans in working memory (WM) after being distracted or interrupted? The present EEG study investigated this question using a WM task in which a random sequence of single numbers (1-4 and 6-9) was presented. In a given trial, participants had to decide whether the number presented in the preceding trial was odd or even. Additionally, interfering stimuli were randomly presented in 25% of all trials, requiring the participants to either ignore a colored number (distraction) or respond to it (interruption) while maintaining the previously formed action plan in WM. Our results revealed a detrimental impact of interruptions on WM performance in trials after interrupting stimuli compared to trials without a preceding interference. This was reflected in decreased task accuracy and reduced stimulus- and response-locked P3b amplitudes potentially indicating a hampered reactivation of stimulus-response links. Moreover, decreased contralateral mu suppression prior to a given response highlighted an impaired response preparation following interruptions. Distractions, on the other hand, did not negatively affect task performance but were followed by faster responses in subsequent trials compared to trials without prior interference. This result pattern was supported by stronger contralateral mu suppression indicating a facilitated response preparation. Overall, these results suggest that action representations in WM are resistant to distractions but do suffer from interruptions that disrupt or interfere with their implementation. We thus propose that the possibility of adequately preparing for an upcoming response is essential for behavioral guidance in the presence of external interference.

Encoding, storage, and response preparation-Distinct EEG correlates of stimulus and action representations in working memory.

Working memory (WM) allows for the active storage of stimulus- and higher level representations, such as action plans. This electroencephalography (EEG) study investigated the specific electrophysiological correlates dissociating action-related from stimulus-related representations in WM using three different experimental conditions based on the same stimulus material. In the experiment, a random sequence of single numbers (from 1 to 6) was presented and participants had to indicate whether the current number (N0 condition), the preceding number (N-1 condition), or the sum of the current and the preceding number (S-1 condition) was odd or even. Accordingly, participants had to store a stimulus representation in S-1 and an action representation in N-1 until the onset of the next stimulus. In the EEG, the storage of stimulus representations (S-1) was reflected by a fronto-central slow wave indicating the rehearsal of information that was required for the response in the following trial. In contrast, the storage of action representations (N-1) went along with a posterior positive slow wave, suggesting that the action plan was actively stored in WM until the presentation of the next stimulus. Crucially, preparing for the next response in N-1 was associated with increased contralateral mu/beta suppression, predicting the response time in the given trial. Our findings, thus, show that the WM processes for stimulus- and action representations can be clearly dissociated from each other with a distinct sequence of EEG correlates for encoding, storage, and response preparation.

Multidomain Cognitive Training Transfers to Attentional and Executive Functions in Healthy Older Adults.

Healthy aging is associated with deficits in focused and sustained attention and executive functions. However, cognitive training (CT) provides a promising method to counteract these deficits. In the present randomized controlled study, we examined to what extent CT regimes can improve attention, verbal skills, and inhibition capacities. Over a period of 16 weeks, healthy older adults (65 years and older, mean: 70 years) received a trainer-guided multidomain paper-and-pencil and computerized CT. Pre- and post-training, a battery of psychometric tests was applied that measured the critical functions. This study used two control groups: a passive control and an active control group performing a relaxation training. Compared to a passive control group, the CT led to enhanced performance in the attentional endurance test and the interference list of the Stroop test, whereas no benefits in verbal and crystalized tests were found. Similar effects were found on the attentional endurance compared to the active control group. Additionally, word fluency was enhanced after CT, but the improvement in the Stroop test did not reach significance compared to the active control. The contents of CT were dissimilar to the psychometric tests showing far transfer, whereas no transfer to attentional or memory functions in the daily life assessed by the Cognitive Failures Questionnaire was found. This demonstrates specific gains of multidomain CT on cognitive functions not explicitly trained and lack of transfer to daily activities.

Differential Effects of Interruptions and Distractions on Working Memory Processes in an ERP Study.

Interruptions (interfering stimuli to respond to) and distractions (interfering stimuli to be ignored) have been shown to negatively impact performance, particularly in tasks requiring working memory (WM). This study investigated how these two types of external interference affect task performance and attentional and WM processes as indexed by specific event-related potentials (ERPs) of the EEG. A Continuous Number Task (CNT) was applied, in which participants had to either decide whether the current number (condition without WM load) or the sum of the current and the preceding number (condition with WM load) was odd or even while responding to interlaced single letters (interruptions) or ignoring them (distractions). Contrary to previous research, we did not find external interference to affect performance under WM load. Unexpectedly, our results rather show that performance was significantly improved in trials after distractions compared to before. This effect was reflected particularly in a significantly increased P3 mean amplitude indicating enhanced attentional reallocation to task-relevant stimuli. Interestingly, this P3 effect appeared independent of WM load and also following interruptions. This underpins the account of P3 amplitudes being modulated by the interval between two task-relevant stimuli rather than by overall task-difficulty. Moreover, a pronounced fronto-central and posterior slow wave following interference suggest more control resources to maintain task-relevant stimuli in WM independent of the preceding interfering stimulus. Our results thus suggest that the type and foreknowledge of external interference may modulate the amount of interference and may also facilitate resource preparation under WM load.

Multitasking in aging: ERP correlates of dual-task costs in young versus low, intermediate, and high performing older adults.

With large inter-individual variability, older adults show a decline in cognitive performance in dual-task situations. Differences in attentional processes, working memory, response selection, and general speed of information processing have been discussed as potential sources of this decline and its between-subject variability. In comparison to young subjects (n = 36, mean age: 25 years), we analyzed the performance of a large group of healthy elderly subjects (n = 138, mean age: 70 years) in a conflicting dual-task situation (PRP paradigm). Based on their dual-task costs (DTCs), the older participants were clustered in three groups of high, medium, and low performing elderly. DTCs differed between groups and increased linearly from young subjects to low performing elderly. The groups did not differ with respect to ERP-components related to task preparation (CNV) and recall of stimulus-response mappings (P2). Peak latencies of the frontocentral P2 and N2 were shorter in young as compared to older adults but did not differ between elderly performance groups. However, differences in N2 amplitude between short and long SOA were correlated with the corresponding DTCs, suggesting more efficient S-R implementation in subjects with lower DTCs. Based on our results, between-subject differences in dual-task interference can be explained in terms of individual differences in selection of an appropriate response in dual-task situations.

What Does the n-Back Task Measure as We Get Older? Relations Between Working-Memory Measures and Other Cognitive Functions Across the Lifespan.

Working memory (WM) declines with increasing age. The WM capacity is often measured by means of the computerized version of the n-back task. Although the n-back task is widely used in aging research, little is known about its construct validity and specific cognitive functions involved in this task. Moreover, to date, no studies analyzed the construct validity as a function of age. To this end, we conducted a study in a sample of N = 533 individuals aged between 20 and 80 years. The sample was divided into three age groups: young (20-40), middle-aged (41-60), and old (61-80 years). A number of psychometric tests was selected that measure attention, memory, and executive control to elucidate the impact of these constructs on n-back performance. A series of correlation analyses was conducted to assess the relationship between n-back performance and specific cognitive functions in each age group separately. The results show a progressive increase in reaction times and a decrease in the proportion of detected targets from young to old subjects. Age-related impairments were also found in all psychometric tests except for the vocabulary choice test measuring crystallized intelligence. Most importantly, correlations yielded different age-related patterns of functions contributing to performance in the n-back task: whereas performance was most related to executive functions in young age, a combination of attentional and executive processes was associated with performance in middle-aged subjects. In contrast, in older age, mainly attentional, verbal memory, and updating and to a lesser extent executive processes seem to play a crucial role in the n-back task, suggesting a shift of processing strategies across the lifespan.

Counting does not improve the accuracy of long time productions.

It is common to use counting strategies to produce time intervals accurately. Does counting improve the accuracy (deviation of produced duration from veridical duration) and precision (variability of produced duration) of time productions in the range of seconds to minutes? In a series of experiments, we compared chronometric counting to intuitive timing (no counting) and to attentional control (simultaneously performing mental arithmetic). In a field experiment, participants had to produce time intervals of 60-s duration in a classroom setting. Relative to intuitive timing, counting did not improve the accuracy (absolute error) of time productions but led to overproduction of duration (larger constant error). In four laboratory experiments, we tested the effects of counting on time production of 10-, 30-, 45-, 60-, and 90-s intervals. Consistently, counting did not improve the accuracy of time production. The relative overproduction due to counting was replicated for long intervals (60 and 90 s) but disappeared at shorter intervals. However, across all intervals tested, counting had positive effects on the precision of time production. As expected, mental arithmetic impaired accuracy and precision and led to overproduction of duration, indicating that participants followed instructions. Based on the experimental data, the overproduction of longer intervals due to counting can neither be explained in terms of attentional processes nor by means of a word-length effect when counting multisyllabic numbers or when participants switch their pace of counting from mono- to multisyllables.

Time perception in depression: a meta-analysis.

BACKGROUND: Depressive patients frequently report to perceive time as going by very slowly. Potential effects of depression on duration judgments have been investigated mostly by means of four different time perception tasks: verbal time estimation, time production, time reproduction, and duration discrimination. Ratings of the subjective flow of time have also been obtained. METHODS: By means of a classical random-effects meta-regression model and a robust variance estimation model, this meta-analysis aims at evaluating the inconsistent results from 16 previous studies on time perception in depression, representing data of 433 depressive patients and 485 healthy control subjects. RESULTS: Depressive patients perceive time as going by less quickly relative to control subjects (g=0.66, p=0.033). However, the analyses showed no significant effects of depression in the four time perception tasks. There was a trend towards inferior time discrimination performance in depression (g=0.38, p=0.079). The meta-regression also showed no significant effects of interval duration. Thus, the lack of effects of depression on timing does not depend on interval duration. However, for time production, there was a tendency towards overproduction of short and underproduction of long durations in depressive patients compared to healthy controls. LIMITATIONS: Several aspects, such as influences of medication and the dopaminergic neurotransmitter system on time perception in depression, have not been investigated in sufficient detail yet and were therefore not addressed by this meta-analysis. CONCLUSIONS: Depression has medium effects on the subjective flow of time whereas duration judgments basically remain unaffected.

Depression does not affect time perception and time-to-contact estimation.

Depressed patients frequently report a subjective slowing of the passage of time. However, experimental demonstrations of altered time perception in depressed patients are not conclusive. We added a timed action task (time-to-contact estimation, TTC) and compared this indirect time perception task to the more direct classical methods of verbal time estimation, time production, and time reproduction. In the TTC estimation task, the deviations of the estimates from the veridical values (relative errors) revealed no differences between depressed patients (N= 22) and healthy controls (N= 22). Neither did the relative errors of the TTC estimates differ between groups. There was a weak trend toward higher variability of the estimates in depressed patients but only at the shortest TTC and at the fastest velocities. Time experience (subjective flow of time) as well as time perception in terms of interval timing (verbal estimation, time production, time reproduction) performed on the same subjects likewise failed to produce effects of depression. We conclude that the notion that depression has a sizeable effect on time perception cannot be maintained.