Relaxing and stimulating effects of odors on time perception and their modulation by expectancy.

Although several studies have reported relaxing and stimulating effects of odors on physiology and behavior, little is known about their underlying mechanisms. It has been proposed that participant expectancy could explain these activation effects. Since emotional stimuli are known to modulate time perception, here we used the temporal bisection task to determine whether odors have objective relaxing and stimulating effects by respectively slowing down or speeding up the internal clock and whether prior expectancy could alter these effects. In Experiment 1, 118 participants were presented either with a strawberry odor or an odorless blank. In Experiment 2, 132 participants were presented either with a lemon odor or an odorless blank. In both experiments, expectancy was manipulated using suggestion (verbal instructions). The stimulus was either described as relaxing or stimulating, or was not described. In the absence of prior suggestion, findings showed that, compared to participants presented with an odorless blank, participants presented with the strawberry odor underestimated sound durations (i.e., a relaxing effect) whereas participants presented with the lemon odor overestimated them (i.e., a stimulating effect). These results confirm that pleasant odors can have objective relaxing and stimulating effects by themselves, which are better explained by arousal-based mechanisms rather than attentional distraction. Furthermore, in both experiments, incongruent suggestions undid the effects of both odors without reversing them completely (i.e., strawberry did not become stimulating even if participants were told so). Both these bottom-up and top-down influences should be considered when investigating the emotional impact of odors on human behavior.

One psychological second does not necessarily last 1000 ms.

The duration of the representation of 1 s was estimated with two methods: (a) the adjustments of the duration of a sound and (b) the production of 10 s with counts from 1 to 11. The estimations were not close to 1 s and varied considerably. Assuming that the representation of 1 s is close to 1000 ms could well be misleading.

Decision-making and dynamics of eye movements in volleyball experts.

Key decision-makers among experts in a given field can sometimes be identified based on their role and responsibilities. The aim of the study is to compare perceptual-cognitive skills of experts with decisional responsibilities (setters in volleyball) with that of other volleyball experts. Eighty-two participants (26 setters, 36 other players and 20 controls) viewed 50 volleyball video sequences. Sequences stopped 120 ms before ball contact and participants, whose eye movements were recorded, had to predict the ball direction. Generalized Estimating Equations analysis revealed that setters and controls made more but shorter fixations than other players. However, both expert groups made better predictions than controls. Dynamics analyses of eye movements over time show that, right before ball contact, opposing players' upper body is a most relevant attentional cue in all game situations. Results are discussed in terms of decision-making responsibilities to identify key decision-makers in volleyball and in general. They point towards specific perceptual-cognitive abilities found in setters and support the idea that they constitute a subgroup of experts, but that they are not "better" than other players in anticipating the game.

An EEG investigation of the mechanisms involved in the perception of time when expecting emotional stimuli.

The main goal of the current study was to identify the electrophysiological signatures of the mechanisms involved in the perception of time when expecting positive, neutral or negative stimuli that have equal arousal levels. Participants were asked to compare the duration of time intervals with a 2-sec reference interval. The color of circles marking a given comparison interval signaled the valence of the upcoming stimulus to be presented, each stimulus being drawn from the International Affective Picture System (IAPS). The behavioral data suggest that time distortion can be induced by the expectation of stimuli with different valences and that expecting a negative stimulus leads to an overestimation of time. The electrophysiological data, more specifically the N150, N200, LPP and CNV components, provide evidence of the implication of attentional mechanisms and possibly strategic adjustments of cognitive control for time perception.

Temporal Processing of Joyful and Disgusting Food Pictures by Women With an Eating Disorder.

The present study used the presentation of food pictures and judgements about their duration to assess the emotions elicited by food in women suffering from an eating disorder (ED). Twenty-three women diagnosed with an ED, namely anorexia (AN) or bulimia nervosa (BN), and 23 healthy controls (HC) completed a temporal bisection task and a duration discrimination task. Intervals were marked with emotionally pre-rated pictures of joyful and disgusting food, and pictures of neutral objects. The results showed that, in the bisection task, AN women overestimated the duration of food pictures in comparison to neutral ones. Also, compared to participants with BN, they perceived the duration of joyful food pictures as longer, and tended to overestimate the duration of the disgusting ones. These effects on perceived duration suggest that AN women experienced an intense reaction of fear when they were confronted to food pictures. More precisely, by having elevated the arousal level and activated the defensive system, food pictures seemed to have speeded up the rhythm of the AN participants' internal clock, which led to an overestimation of images' duration. In addition, the results revealed that, in both tasks, ED women presented a lower temporal sensitivity than HC, which was related to their ED symptomatology (i.e., BMI, restraint and concern) and, particularly, to their weaker cognitive abilities in terms of attention, processing speed and working memory. Considered all together, the findings of the present experiment highlight the role of fear and anxiety in the manifestations of AN and point out the importance of considering non-temporal factors in the interpretation of time perception performance.

Stevens's law for time: A direct comparison of prospective and retrospective judgments.

Participants are aware that they have to perform a temporal task in a prospective timing condition but not in a retrospective timing condition. In the present study, a direct comparison of temporal estimates under each paradigm is proposed via a strategy where each participant is restricted to only 1 response. Participants were assigned to either a prospective or retrospective testing condition and asked to reproduce and then estimate verbally 1 of 6 intervals lasting .5 to 16 s. The analyses based on Stevens's power law were restricted to intervals lasting 2 to 16 s. With a verbal estimate method, the results indicate that the exponent is higher in retrospective than in prospective conditions (1.20 vs. 1.10 for females and 1.31 vs. 1.02 for males, respectively). For the interval reproduction task, the exponent based on Eisler's (1975) model was slightly higher for males (1.13) than for females (1.08) in prospective timing, but slightly higher for females (1.10) than for males (1.04) in retrospective timing. The results based on inferential statistics and the 6 intervals reveal that, with the verbal estimate method, females make significantly larger relative verbal estimates than males and, at 16 s, intervals were judged as longer in the retrospective than in the prospective condition; with the reproduction method, the perceived duration is about the same in each paradigm and there is no significant sex effect. Overall, the data do not confirm that temporal intervals are perceived as longer in the prospective than in the retrospective conditions.

Do not count too slowly: evidence for a temporal limitation in short-term memory.

Some data in the time perception literature have indicated that Weber's law for time does not hold: The Weber fraction gets higher with longer intervals. It is posited that this increase may reflect a fundamental information-processing limitation. If that is true, counting at a pace at which the intervals between counts remain within this capacity limitation should be more accurate than counting with intervals exceeding this capacity. In a task in which participants had to count up to a target number for a series of trials, the variability of the durations covered for reaching the target was higher when the intercount interval lasted 1,600 ms than when it lasted 800 ms. This finding provides evidence pointing toward the existence of a fundamental temporal limitation for processing information efficiently.

Foreperiod and range effects on time interval categorization.

One factor influencing the perceived duration of a brief interval is the length of the period preceding it, namely the foreperiod (FP). When multiple FPs are varied randomly within a testing session, longer FPs result in longer perceived duration. The purpose of this study was to identify what characteristics modulate this effect. In a task where participants were asked to categorize the duration of target intervals with respect to a 100-ms standard, the FPs were distributed over a 150-, 300-, or 900-ms range with the midpoint (1000 ms) of these distributions being kept constant. The results indicate that the effect of the length of variable FPs on perceived duration was much stronger in the 900-ms range condition. More specifically, this effect is due to the differences between the shortest FPs. The results also reveal that, overall, there are more short responses in the 300-ms condition than in the other range conditions. Moreover, the data reveal that the narrower the distribution, the better the discrimination. One interpretation of the main result (range effect) is that a wider distribution leads to an increased prior uncertainty towards the foreperiod length.

Effect on perceived duration and sensitivity to time when observing disgusted faces and disgusting mutilation pictures.

The aim of this study was to compare the effect on interval discrimination of the presentation of disgusting mutilation images and the presentation of faces expressing disgust. In Experiments 1 and 2, participants had to say whether the second of two images was presented for a shorter or a longer duration than the first (intervals = 400 ms vs. 482 ms). Although the overall probability of responding "long" was not exactly the same in these two experiments, participants reported that duration was longer more often when disgusting mutilation images were presented than when neutral or disgusted faces were presented. In Experiment 3, in which a single-stimulus method was employed, mutilation images were once again reported to be presented for a longer duration than neutral or disgusted faces. The investigation also reveals that discrimination levels are not higher when mutilation images are presented. It is argued that the effect of mutilation images on perceived duration is not due to attention; it is rather attributed to the increased arousal caused by these images.

Discrimination of two neighboring intra- and intermodal empty time intervals marked by three successive stimuli.

We investigated the discrimination of two neighboring intra- or inter-modal empty time intervals marked by three successive stimuli. Each of the three markers was a flash (visual-V) or a sound (auditory-A). The first and last markers were of the same modality, while the second one was either A or V, resulting in four conditions: VVV, VAV, AVA and AAA. Participants judged whether the second interval, whose duration was systematically varied, was shorter or longer than the 500-ms first interval. Compared with VVV and AAA, discrimination was impaired with VAV, but not so much with AVA (in Experiment 1). Whereas VAV and AVA consisted of the same set of single intermodal intervals (VA and AV), discrimination was impaired in the VAV compared to the AVA condition. This difference between VAV and AVA could not be attributed to the participants' strategy to perform the discrimination task, e.g., ignoring the standard interval or replacing the visual stimuli with sounds in their mind (in Experiment 2). These results are discussed in terms of sequential grouping according to sensory similarity.