Meeting of minds: Skinner and Michotte at the International Congress of Psychology, Stockholm, 1951.

This note discusses the apparently unpublished correspondence between B. F. Skinner and the Belgian psychologist Albert Michotte, preceding Skinner's visit to the Thirteenth International Congress of Psychology in Stockholm in 1951. Skinner's letters, written in French, were intended to arrange a visit to Michotte's laboratory in Leuven (then called Louvain) in Belgium, which in the end never took place, although it seems highly likely that they met in Stockholm. There is no record of the topic of the conversations they may have had, although one possible speculation concerns discussions of causality, as both Skinner and Michotte had published work relating to this topic in the 1940s, Michotte's La Perception de la Causalité and Skinner's Superstition in the pigeon. The note also discusses the way in which Skinner's visit to the Thirteenth Congress influenced the development of the experimental analysis of behavior in both Europe and Japan.

Filling your time: Auditory flutter alters perceived duration via stimulus-locked responses.

In the current article, we examined the flutter-duration illusion; the extension of perceived duration when an interval is filled with auditory flutter. Participants reproduced flutter-filled and empty durations while electrophysiological activity was recorded. As expected, participants over-produced durations when they were filled with auditory flutter rather than unfilled. Using multivariate pattern analysis, we found several differentiating patterns of neural activity while participants listened to either flutter-filled or empty intervals. However, in subsequent single trial analysis, only two of these clusters predicted perceived duration in the flutter condition; one occurring in line with the second click of the flutter, and one in line with the fourth click. We relate this finding to the N1P2 component and P3a component to timing initiation and arousal, respectively.

Can't catch the beat: Failure to find simple repetition effects in three types of temporal judgements.

More experience results in better performance, usually. In most tasks, the more chances to learn we have, the better we are at it. This does not always appear to be the case in time perception however. In the current article, we use three different methods to investigate the role of the number of standard example durations presented on performance on three timing tasks: rhythm continuation, deviance detection, and final stimulus duration judgement. In Experiments 1a and 1b, rhythms were produced with the same accuracy whether one, two, three, or four examples of the critical duration were presented. In Experiment 2, participants were required to judge which of four stimuli had a different duration from the other three. This judgement did not depend on which of the four stimuli was the deviant one. In Experiments 3a and 3b, participants were just as accurate at judging the duration of a final stimulus in comparison to the prior stimuli regardless of the number of standards presented prior to the final stimulus. In summary, we never found any systematic effect of the number of standards presented on performance on any of the three timing tasks. In the discussion, we briefly relate these findings to three theories of time perception.

The Dawn of the Study of Motor Timing: Wilhelm Camerer (1866) and Karl von Vierordt (1868) on the Time Course of Voluntary Movements.

This article discusses material from the doctoral thesis of Wilhlem Camerer, which was devoted to the topic of the timing of voluntary movements, and appeared in 1866, thus being one of the earliest studies of any aspect of time perception. It was conducted under the supervision of Karl von Vierordt, at the University of Tübingen in Germany. The data reported come from Camerer's attempts to make a movement over a distance of about 65 mm, either by flexion or extension of his arm, with the behavior recorded via a kymograph, and measured from its trace. Most of his data come from his attempts to make movements at a constant speed, with the speed varying from one trial to another from 5 to 60 mm/s, but he also conducted a study where the movement was intended to be accelerated or decelerated during the trial. In general, when extension movements were intended to be performed with constant speed, a gradual increase in movement speed usually occurred throughout the movement duration. For flexions the opposite occurred, albeit less clearly. Camerer linked the apparent distortions of speed to Vierordt's experiments on the perception of time and his thesis contains what is probably the first mention of Vierordt's Law, the proposition that short times are judged as longer, and long times as shorter, than they really are.

Executive processes and timing: Comparing timing with and without reference memory.

Temporal perception is influenced by executive function. However, performance on different temporal tasks is often associated with different executive functions. This study examined whether using reference memory during a task influenced how performance was associated with executive resources. Participants completed temporal generalisation and bisection tasks, in their normal versions involving reference memory and in episodic versions without reference memory. Each timing task had two difficulty levels: easy and hard. Correlations between performance on these tasks and measures of executive function (updating, inhibition, task switching, and access to semantic memory) were assessed. Accuracy on the temporal generalisation task was correlated with memory access for all versions of the task. Updating correlated with accuracy only for the reference memory-based version of the task. Temporal bisection performance presented a different pattern of correlations. The bisection point was negatively correlated with inhibition scores, except for the easy episodic condition. The Weber ratio, considered a measure of temporal sensitivity, was negatively correlated with memory access only in the hard episodic condition. Together, the findings suggest that previous models of generalisation and bisection may not accurately reflect the underlying cognitive processes involved in the tasks.

Short-term effects on temporal judgement: Sequential drivers of interval bisection and reproduction.

Our prior experiences provide the background with which we judge subsequent events. In the time perception literature one common finding is that providing participants with a higher percentage of a particular interval can skew judgment; intervals will appear longer if the distribution of intervals contains more short experiences. However, changing the distribution of intervals that participants witness also changes the short-term, interval-to-interval, sequence that participants experience. In the experiment presented here, we kept the overall distribution of intervals constant while manipulating the immediately-prior experience of participants. In temporal bisection, this created a noted assimilation effect; participants judged intervals as shorter given an immediately preceding short interval. In interval reproduction, there was no effect of the immediately prior interval length unless the prior interval had a linked motor command. We thus proposed that the immediately prior interval provided a context by which a subsequent interval is judged. However, in the case of reproduction, where a subsequent interval is reproduced, rather than seen, the effects of contextualization are attenuated.

Experience Sampling Methodology reveals similarities in the experience of passage of time in young and elderly adults.

Many people accept the idea that time seems to pass more quickly as they get older, as if this is a psychological reality. However, systematic investigations of differences in judgments of passage of time between young and elderly people are very rare and contradictory. The present study examined the experience of passage of time in daily life in young and elderly people using Experience Sampling Methodology (ESM), with 8 alerts per day for 5 days being delivered by smartphones. At each alert, a short questionnaire was filled in, asking questions about passage of present time, affective state, arousal level, and attention to current activities, among others. Our ESM study found no difference between the young and the old participants in the judgment of passage of present time. Irrespective of the participants' age, the experience of passage of time in every-day life was significantly related to affective states and current activities when they captured attention.

The differential contribution of executive functions to temporal generalisation, reproduction and verbal estimation.

Evidence from dual-task studies suggests that executive resources are recruited during timing. However, there has been little exploration of whether executive recruitment is universal across temporal tasks, or whether different temporal tasks recruit different executive resources. The current study explored this further by examining how individual differences in updating, switching, inhibition and access affected performance on temporal generalisation, reproduction and verbal estimation tasks. It was found that temporal tasks differentially loaded onto different executive resources. Temporal generalisation performance was related to updating and access ability. Reproduction performance was related to updating, access and switching. Verbal estimation performance was only related to access. The results suggest that executive resources may be recruited when monitoring and maintaining multiple durations in memory at the same time, and when retrieving duration representations from long-term memory. The findings emphasise the need to consider timing behaviour as the product of a wide range of complex, integrated, cognitive systems, rather than as the output of a clock in isolation.

Females' duration estimates of briefly-viewed male, but not female, photographs depend on attractiveness.

We tested a prediction that females' duration estimates of briefly-viewed male, but not female, photos would be modulated by attractiveness. Twenty-seven female participants viewed sequences of five stimuli of identical duration in which the first four were sine-wave gratings (Gabor discs) and the fifth was either the same sine-wave grating (control trials) or a photo of an attractive or unattractive male or female (test trials). After each sequence, participants had to reproduce the duration of the fifth stimulus. Results confirmed our prediction and showed that duration estimates of attractive male photos were significantly longer than corresponding estimates for unattractive male photos, while there was no significant difference in estimated duration for attractive and unattractive female photos. Our data show that unexpectedly viewing an attractive male affects time perception in females, and are the first demonstration that stimuli relevant to reproductive fitness, which engage the appetitive motivational system, can increase perceived duration.

The cognitive neuroscience of time perception: how psychological studies might help to dissect the timing system.

It is argued that the cognitive neuroscience of time perception does not make sufficient use of a range of experimental techniques and theoretical approaches which might be useful in "dissecting" the human timing system, and thus helping to uncover its neural basis. These techniques are mostly inspired by scalar expectancy theory, but do not depend on acceptance of that model. Most of the methods result in the same physical stimuli giving rise to systematically different time judgements, thus they avoid problems of control which have haunted some areas of the cognitive neuroscience of timing. Among the possibilities are (a) changing the basic duration judgement of stimuli and events, (b) manipulating working memory and reference memories for duration, and (c) changing temporal decision processes.

Explaining between-group differences in performance on timing tasks.

The article discusses interpretation of between-group differences in performance on timing tasks. First, it is shown that differences in internal clock "pacemaker speed" cannot normally be used as a coherent explanation of obtained effects, even if such differences in pacemaker speed exist. Secondly, it is shown how, in theory, modelling of performance on commonly used timing tasks like bisection and temporal generalization can illuminate between-group effects. Thirdly, the article discusses some examples of such modelling from published work and shows how some between-group differences--for example, between children of different ages, or between patients and controls--have been explained. Finally, some ambiguities in modelling are discussed--for example, the fact that different explanations of differences in performance on timing tasks between groups may be difficult or impossible to distinguish in practice.

Interference between auditory and visual duration judgements suggests a common code for time.

Auditory stimuli usually have longer subjective durations than visual ones for the same real duration, although performance on many timing tasks is similar in form with different modalities. One suggestion is that auditory and visual stimuli are initially timed by different mechanisms, but later converted into some common duration code which is amodal. The present study investigated this using a temporal generalization interference paradigm. In test blocks, people decided whether comparison durations were or were not a 400-ms standard on average. Test blocks alternated with interference blocks where durations were systematically shorter or longer than in test blocks, and interference was found, in the direction of the durations in the interference blocks, even when the interfering blocks used stimuli in a different modality from the test block. This provides what may be the first direct experimental evidence for a "common code" for durations initially presented in different modalities at some level of the human timing system.

More consistent, yet less sensitive: interval timing in autism spectrum disorders.

Even though phenomenological observations and anecdotal reports suggest atypical time processing in individuals with an autism spectrum disorder (ASD), very few psychophysical studies have investigated interval timing, and the obtained results are contradictory. The present study aimed to clarify which timing processes function atypically in ASD and whether they are related to the ASD diagnostic profile. Visual, auditory, and cross-modal interval timing was assessed in 18 individuals with ASD using a repeated standards version of the temporal generalization task. The use of two different standard durations (600 and 1,000 ms) allowed for an assessment of the scalar property of interval timing in ASD, a fundamental characteristic of interval timing. The ASD group showed clearer adherence to the scalar property of interval timing than the control group. In addition, both groups showed the normal effect that auditory stimuli had longer subjective durations than visual ones. Yet, signal detection analysis showed that the sensitivity of temporal discrimination was reduced in the ASD group across modalities, in particular for auditory standards. Moreover, response criteria in the ASD group were related to symptom strength in the communication domain. The findings suggest that temporal intervals are fundamentally processed in the same way in ASD and TD, but with reduced sensitivity for temporal interval differences in ASD. Individuals with ASD may show a more conservative response strategy due to generally decreased sensitivity for the perception of time intervals.

Perception of short time scale intervals in a hypnotic virtuoso.

Previous studies showed that hypnotized individuals underestimate temporal intervals in the range of several seconds to tens of minutes. However, no previous work has investigated whether duration perception is equally disorderly when shorter time intervals are probed. In this study, duration perception of a hypnotic virtuoso was tested using repeated standard temporal generalization and duration estimation tasks. When compared to the baseline state, hypnosis affected perception of intervals spread around 600 ms in the temporal generalization task but did not alter perception of slightly longer intervals spread around 1000 ms. Furthermore, generalization of temporal intervals was more orderly under hypnosis than in the baseline state. In contrast, the hypnotic virtuoso showed a typical time underestimation effect when perception of longer supra-second intervals was tested in the duration estimation task, replicating results of the previous hypnosis studies.

The effect of alcohol administration on human timing: a comparison of prospective timing, retrospective timing and passage of time judgements.

Previous research suggests that human timing may be affected by alcohol administration. The current study aimed to expand on previous research by examining the effect of alcohol on prospective timing, retrospective timing and passage of time judgements. A blind between-subjects design was employed in which participants were either administered 0 g of alcohol per kilogramme of body weight (placebo), 0.4 g/kg (low dose) or 0.6g/kg (high dose). Participants completed four types of temporal task; verbal estimation and temporal generalisation, a retrospective timing task and a passage of time judgement task. A high dose of alcohol resulted in overestimations of duration relative to the low dose and placebo group in the verbal estimation task. A high dose of alcohol was also associated with time passing more quickly than normal. Alcohol had no effect on retrospective judgements. The results suggest that a high dose of alcohol increases internal clock speed leading to over-estimations of duration on prospective timing tasks, and the sensation of time passing more quickly than normal. The absence of an effect of alcohol on retrospective timing supports the suggestion that retrospective judgements are not based on the output of an internal clock.

Why do temporal generalization gradients change when people make decisions as quickly as possible?

Three experiments investigated temporal generalization performance under conditions in which participants were instructed to make their decisions as quickly as possible (speed), or were allowed to take their time (accuracy). A previous study (Klapproth & Müller, 2008) had shown that under speeded conditions people were more likely to confuse durations shorter than the standard with the standard than in the accuracy conditions, and a possible explanation of this result is that longer stimulus durations are "truncated" (i.e., people make a judgement about them before they have terminated, thereby shortening their effective duration) and that these truncated durations affect the standard used for the task. Experiment 1 investigated performance under speed and accuracy conditions when comparison durations were close to the standard or further away. No performance difference was found as a function of stimulus spacing, even though responses occurred on average before the longest durations had terminated, but this lack of effect was attributed to "task difficulty" effects changing decision thresholds. In Experiment 2, the standard duration was either the longest or the shortest duration in the comparison set, and differences between speed and accuracy groups occurred only when the comparisons were longer than the standard, supporting the "truncation" hypothesis. A third experiment showed that differences between speed and accuracy groups only occurred if some memory of the standard that was valid for more than one trial was used. In general, the results suggest that the generalization gradient shifts in speeded conditions occur because of truncation of longer comparison durations, which influences the effective standard used for the task.

Psychophysical assessment of timing in individuals with autism.

Perception of time, in the seconds to minutes range, is not well characterized in autism. The required interval timing system (ITS) develops at the same stages during infancy as communication, social reciprocity, and other cognitive and behavioral functions. The authors used two versions of a temporal bisection procedure to study the perception of duration in individuals with autism and observed quantifiable differences and characteristic patterns in participants' timing functions. Measures of timing performance correlated with certain autism diagnostic and intelligence scores, and parents described individuals with autism as having a poor sense of time. The authors modeled the data to provide a relative assessment of ITS function in these individuals. The implications of these results for the understanding of autism are discussed.

Stimulus intensity and the perception of duration.

This article explores the widely reported finding that the subjective duration of a stimulus is positively related to its magnitude. In Experiments 1 and 2 we show that, for both auditory and visual stimuli, the effect of stimulus magnitude on the perception of duration depends upon the background: Against a high intensity background, weak stimuli are judged to last longer. In Experiment 3 we show that the effect of intensity becomes more pronounced at longer durations, consistent with the idea that stimulus intensity affects the pacemaker component of an internal clock, and that it is the difference of a stimulus from the background, rather than its absolute magnitude, which influences the rate of the pacemaker. These results urge a modification to the oft-repeated claim that more intense stimuli seem to last longer, and provide an important constraint on any model of human timing.

Click trains and the rate of information processing: does "speeding up" subjective time make other psychological processes run faster?

A series of experiments demonstrated that a 5-s train of clicks that have been shown in previous studies to increase the subjective duration of tones they precede (in a manner consistent with "speeding up" timing processes) could also have an effect on information-processing rate. Experiments used studies of simple and choice reaction time (Experiment 1), or mental arithmetic (Experiment 2). In general, preceding trials by clicks made response times significantly shorter than those for trials without clicks, but white noise had no effects on response times. Experiments 3 and 4 investigated the effects of clicks on performance on memory tasks, using variants of two classic experiments of cognitive psychology: Sperling's (1960) iconic memory task and Loftus, Johnson, and Shimamura's (1985) iconic masking task. In both experiments participants were able to recall or recognize significantly more information from stimuli preceded by clicks than those preceded by silence.

Are memories for duration modality specific?

Four experiments examined the effects of encoding multiple standards in a temporal generalization task in the visual and auditory modalities both singly and cross-modally, using stimulus durations ranging, across different experiments, from 100 to 1,400 ms. Previous work has shown that encoding and storing multiple auditory standards of different durations resulted in systematic interference with the memory of the standard, characterized by a shift in the location of peak responding, and this result, from Ogden, Wearden, and Jones (2008), was replicated in the present Experiment 1. Experiment 2 employed the basic procedure of Ogden et al. using visual stimuli and found that encoding multiple visual standards did not lead to performance deterioration or any evidence of systematic interference between the standards. Experiments 3 and 4 examined potential cross-modal interference. When two standards of different modalities and durations were encoded and stored together there was also no evidence of interference between the two. Taken together, these results, and those of Ogden et al., suggest that, in humans, visual temporal reference memory may be more permanent than auditory reference memory and that auditory temporal information and visual temporal information do not mutually interfere in reference memory.