Experiments on subjective duration 1868-1975: A collection of power function exponents.

Exponents of the psychophysical function for subjective duration are compiled from 111 studies undertaken with the methods of magnitude estimation, magnitude production, and ratio setting. The determination of exponents from ratio-setting data is based on a new model for time perception that also allows the computation of exponents from equal-setting (duration reproduction) data (i.e., from experiments that did not involve the S's numerical behavior). The following problems are dealt with in terms of their influence on the exponent of subjective duration: practice, sensory modality (used in presenting the duration, including empty intervals), drugs, group differences (age, mental retardation, psychosis, neurosis), and experimental effects (methods, very short durations, intramodal range effect). A general conclusion is that time perception is not veridical and that the exponent on the average approximates 0.9. (4 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

5-Hydroxytryptamine1D-like receptors mediate contraction of partially depolarized rabbit renal arteries

OBJECTIVE: Our purpose was to correlate measures of Doppler-detected fetal movements with standard fetal heart rate parameters and perinatal outcomes. STUDY DESIGN: This prospective, multiinstitutional trial used the Hewlett-Packard M1350A monitor to record simultaneous fetal heart rate baseline, variability, accelerations, decelerations, and number of fetal movements, and duration and percent of total time. These data were compared at 10- and 30-minute intervals during nonstress tests and were correlated with fetal heart rate baseline parameters and maternally perceived fetal movements and with outcomes of infants delivered within 7 days of the last test. RESULTS: At six centers 1704 actocardiograms from 884 third-trimester patients were analyzed. Doppler-detected fetal movement counts, durations, and percent of total time correlated weakly with all baseline fetal heart rate parameters (all values < 0.20). All fetal movement parameters increased significantly in successive 10-minute blocks and in periods of increased or normal fetal heart rate variability compared with those with fetal heart rate variability. The sensitivity, specificity, and predictive values of the percent of total movement time were comparable to those of standard nonstress test parameters. The risk of poor perinatal outcomes after nonreactive nonstress tests was lower in cases with fetal movements than in those without. CONCLUSIONS: Doppler actocardiography may help to discriminate fetal states during antepartum testing. It may prevent inappropriate diagnosis of fetal compromise when the nonstress test is nonreactive or nonreassuring.     

Discrimination of temporal relations by pigeons.

In 4 experiments, pigeons were tested on a duration comparison task involving the successive presentation of two visual stimuli that varied in duration from trial to trial. Following presentation of the durations, 2 choice keys were lit, and reinforcement for choices was based on the temporal relation between durations of the pair. In Exp 1, the range of durations was varied over conditions. Responding changed as an orderly function of the ratio of the 2 durations. There was a decrease in discrimination accuracy as average duration increased over conditions. In Exp 2, Ss were transferred from a task involving spatially differentiated choices to one involving hue-differentiated choices. Performance was similar to that of Exp 1. In Exp 3, Ss were exposed to a single duration range that included many durations from the 4 ranges of Exp 1. Discrimination accuracy was comparable on 3 problem duration categories within this range and declined slightly for problems in the 4th and longest category. Manipulation of absolute reinforcement rate in Exp 4 resulted in no change in discrimination accuracy, suggesting that the decline in accuracy over conditions of Exp 1 could not be attributed to decreases in reinforcement rate that accompanied lengthier durations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial effects on tactile duration categorization.

The aim of this study was to measure the impact of the distance between tactile stimuli marking brief time intervals on perceived duration and threshold estimates. Each interval to be categorized as short or long (midvalue = 500 ms) was marked by two brief signals delivered on participants' left (L) or right (R) hand: L-L, R-R, L-R or R-L. The hands were placed nearby or at a distance of 3 feet (about 91 cm). Eight-point individual psychometric functions were drawn for each of the eight experimental conditions. The results reveal that when intervals are marked with signals delivered on different hands rather than on the same hand, they are perceived as longer. Moreover, no difference for perceived duration was observed between the L-L and R-R conditions, and between the L-R and R-L sequence. Finally, marking intervals with signals delivered at the same hand results in better temporal discrimination than with one signal delivered on each hand. The results with perceived duration are consistent with the kappa effect, but not with an attentional account of duration discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Short-term memory and time estimation: Beyond the 2-second "critical" value.

The authors showed previously that when time intervals around two sec are reproduced concurrently with a memory task, intervals are positively related to duration of memory processing. However, some data in research on timing as well as in memory research suggest that 2 sec might be a critical duration beyond which different mechanisms or structures would support performance. This implies that the interference observed between memory processing and 2-sec productions could be specific to these durations, and would not be obtained with longer durations. In this experiment, intervals ranging from 1.85 to 6.45 sec were reproduced by participants (16 females and 12 males, aged 18-33 yrs), who were searching simultaneously for a memory probe. At all durations, reproductions were positively related to memory set size. These findings have implications with regards to previous research indicating a discontinuity around 2-3 sec in time perception. They suggest in particular that the role of memory is similar in reproduction of durations around 2 sec and of longer durations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

How emotional auditory stimuli modulate time perception.

Emotional and neutral sounds rated for valence and arousal were used to investigate the influence of emotions on timing in reproduction and verbal estimation tasks with durations from 2 s to 6 s. Results revealed an effect of emotion on temporal judgment, with emotional stimuli judged to be longer than neutral ones for a similar arousal level. Within scalar expectancy theory (J. Gibbon, R. Church, & W. Meck, 1984), this suggests that emotion-induced activation generates an increase in pacemaker rate, leading to a longer perceived duration. A further exploration of self-assessed emotional dimensions showed an effect of valence and arousal. Negative sounds were judged to be longer than positive ones, indicating that negative stimuli generate a greater increase of activation. High-arousing stimuli were perceived to be shorter than low-arousing ones. Consistent with attentional models of timing, this seems to reflect a decrease of attention devoted to time, leading to a shorter perceived duration. These effects, robust across the 2 tasks, are limited to short intervals and overall suggest that both activation and attentional processes modulate the timing of emotional events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relationships between infant crying, birth complications, and maternal variables

The aim of the study is to identify factors influencing infants' crying behaviour (total crying duration, length of crying bouts, and frequency of crying). The searching for variables explaining inter-individual differences requires a sufficient stability of the cry parameters at least over short time intervals. Thus, a second aim is to assess the intra-individual stability of the crying behaviour in an age range from 3 to 12 months. Sixty-two mother-child dyads participated in the study. The results show substantial stabilities of the crying behaviour of infants between 3 and 12 months of age. This is related to the amount of crying as well as to the pattern of crying shown by the children over a 24 h interval. The typical cry pattern is characterized by peaks at 12.00 h and early in the evening, although there are large individual differences between the children with regard to cry durations at each hour of the day. Regarding the cry durations at 3 months of age, birth complications and the perceived emotional atmosphere in the mothers' family of origin are the major contributing factors.     

Age-related changes in auditory temporal processing.

Two tone bursts separated by a silent interval and imbedded in a background white noise were presented to elderly subjects (M age?=?71.3 years) and young subjects (M age?=?22.2 years). Subjects were required to judge when the two tone bursts fused perceptually by adjusting the duration of tone-one. The bursts were separated by six discrete interstimulus intervals of 4, 8, 16, 24, 32, or 40 ms. The tone-two burst was held constant at 100 ms. Fusion point was defined as that critical tone-one duration at which the two tones fused (were perceived as one). Elderly subjects reached fusion point at longer critical tone-one durations than young subjects at each interval tested. The function relating tone-one duration and interval conformed to an exponential curve and is discussed with respect to an exponential decay model of the inhibitory interactions of neural systems responding to onsets and offsets of sensory events. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Temporal ventriloquism in a purely temporal context.

This study examines how audiovisual signals are combined in time for a temporal analogue of the ventriloquist effect in a purely temporal context, that is, no spatial grounding of signals or other spatial facilitation. Observers were presented with two successive intervals, each defined by a 1250-ms tone, and indicated in which interval a brief audiovisual stimulus (visual flash + noise burst) occurred later. In “test“ intervals, the audiovisual stimulus was presented with a small asynchrony, while in “probe” intervals it was synchronous and presented at various times guided by an adaptive staircase to find the perceived temporal location of the asynchronous stimulus. As in spatial ventriloquism, and consistent with maximum likelihood estimation (MLE), the asynchronous audiovisual signal was shifted toward the more reliably localized component (audition, for all observers). Moreover, these temporal shifts could be forward or backward in time, depending on the asynchrony order, suggesting perceived timing is not entirely determined by physical timing. However, the critical signature of MLE combination—better bimodal than unimodal precision—was not found. Regardless of the underlying model, these results demonstrate temporal ventriloquism in a paradigm that is defined in a purely temporal context. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Modifiers and Perceived Stress Scale.

Investigated the interrelations between perceived stress and its modifiers (anticipation of events, responsibility for events, and amount of social support from friends and family) and total or averaged scores on a modifiers and perceived stress (MAPS) scale and obtained data on reliability and validity of the MAPS. Factor analysis of total and average scores of 302 men (average age 52 yrs) for these areas identified 4 dimensions: Total and average anticipated and responsible scores loaded on 1 dimension, number of events and total perceived stress loaded on another, the 2 support scores loaded on a 3rd factor, and average perceived stress loaded independently on a factor. Two-week test–retest reliabilities for scores were in the moderate to high range. Independent assessments of stress by social workers correlated significantly with the total perceived stress score and with average perceived stress score. (26 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dynamic contrast perception assessed by pattern masking

The perceived contrast of a pulsed grating varies markedly with the exposure duration and spatial frequency of the grating. We studied dynamic changes in perceived grating contrast with a pattern-masking paradigm. We measured masking of a brief, localized test pattern (a D6 stimulus, 30 ms in duration) by fixed-contrast cosine grating patterns of varying duration (50-500 ms). The cosine mask pattern had spatial frequency of either 1 or 6 cycles per degree (cpd) at a contrast of 0.3. The D6 test pattern was centered on a light bar of the mask and was either positive peak contrast (same-polarity test and mask) or negative peak contrast (opposite-polarity test and mask). In Experiment 1, the test and mask had simultaneous onset. With a 6-cpd mask, the same-polarity test-threshold elevation versus mask-duration function increases monotonically. For a 1-cpd mask, the same-polarity threshold-mask-duration function is nonmonotonic, with peak masking effect produced by a grating pulse of 80-100 ms. These masking effects are closely congruent with known dynamic contrast effects. With negative tests, masking-duration functions are elevated from same-polarity functions and are essentially similar in shape for 1- and 6-cpd masks. The elevated thresholds suggest inhibitory interaction between ON and OFF pathways, with a similar time course across spatial frequency. In Experiment 2, the D6 test was delayed from mask onset by 33 ms. Positive contrasts only were employed. For 1-cpd stimuli, the delay of test greatly reduced masking at all mask durations and eliminated the nonmonotonic function. This suggests that for low-spatial-frequency patterns, perceived contrast is determined by an early peak component of the neural response. But for 6-cpd stimuli, masking of the delayed test was somewhat greater at all mask durations, consistent with a gradually increasing underlying neural response to the grating. Finally, in Experiment 3, same-polarity masking effects at both spatial frequencies were replicated with negative-contrast test and mask (OFF pathway mediation). This indicates that the ON and OFF pathways have similar response dynamics.     

Stimulus dynamics and temporal discrimination: Implications for pacemakers.

The purpose of the present study was to observe the functional relationship between stimulus dynamics and stimulus duration judgments in humans. Stimulus duration was defined as the length of time that a spinning sphere appeared on a computer screen. Stimulus dynamics were defined by how quickly the sphere rotated on its y-axis. Using a logarithmic scale, a psychophysical bisection task was used to divide stimulus durations into two categories, short and long. Across three experiments, participants’ duration judgments were longer the faster the sphere was rotated. This effect was observed over both a long and short temporal scale and over a wide range of stimulus dynamics despite the fact that the reinforcement contingencies penalized participants for this effect. The results are discussed in terms of perceived change as the possible basis of temporal duration estimation. This hypothesis was investigated through applications of the leading quantitative models of temporal discrimination to the present data. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Overloading Temporal Memory.

This study tested the hypothesis that memory is a major source of variance in temporal processing. Participants categorized intervals as short or long. The number of base durations and interval types mixed within blocks of trials varied from 1 session to another. Results revealed that mixing 2 base durations within blocks increased categorization errors, but mixing 2 marker types did not. Results are attributed to the involvement of more than 1 memory representation, which is argued to show the critical role of memory in temporal processing. Because mixing modalities has no such effect, it was argued that modalities share a common representation in memory. Finally, there was no difference in the perceived duration of auditory and visually marked intervals, which is inconsistent with most reports on this effect. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Molecular cloning and characterization of two related and interferon-induced 56-kDa and 30-kDa proteins highly similar to 2''-5'' oligoadenylate synthetase

The capability of subjects to categorize (as short or long) visually marked empty time intervals was investigated in three experiments. Two visual signals, located 18 degrees to the left (L) and to the right (R) of a fixation point in the visual field, established four marking conditions, two unilaterally presented (L-L and R-R) and two bilaterally presented (L-R and R-L). In Experiments 1 and 2, the results show that discrimination is better with unilateral sequences than with bilateral sequences and that the perceived duration is longer with an L-R than with an R-L sequence. In addition, Experiment 2 shows that, in comparison with a condition in which Markers 1 and 2 remain identical for a complete session, varying the markers from trial to trial does not decrease discrimination. Also, Experiment 2 shows that discrimination is better when both visual markers are presented at fovea than it is in the unilateral conditions. Experiment 3 shows that bilateral intervals are perceived as being longer and are better discriminated than are intervals marked by an intermodal sequence (auditory-visual or visual-auditory). The general discussion reports the implications of having different perceived duration and sensitivity levels, in various marker-type conditions, for an internal-clock hypothesis. Some implications of these results for a lateralized-timer hypothesis are also discussed.     

Dynamic attending and responses to time.

A temporally based theory of attending is proposed that assumes that the structure of world events affords different attending modes. Future-oriented attending supports anticipatory behaviors and occurs with highly coherent temporal events. Time judgments, given this attending mode, are influenced by the way an event's ending confirms or violates temporal expectancies. Analytic attending supports other activities (e.g., grouping, counting), and if it occurs with events of low temporal coherence, then time judgments depend on the attending levels involved. A weighted contrast model describes over- and underestimations of event durations. The model applies to comparative duration judgments of equal and unequal time intervals; its rationale extends to temporal productions/extrapolations. Two experiments compare predictions of the contrast model with those derived from other traditional approaches. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The temporal dynamics of tics in Gilles de la Tourette syndrome

BACKGROUND: Statistical characterization of tic behavior in Gilles de la Tourette syndrome (GTS) may provide insight into the dynamic functioning of the human central nervous system, as well as improve the quantitative assessment of tic symptom severity. METHODS: Twenty-two medication-free GTS subjects underwent videotaping of their tics. The intervals between temporally adjacent tics were measured, and the statistical properties of these intervals were assessed through graphical representation of frequency distributions, autoregressive integrated moving average (ARIMA) modeling, spectral analysis, and construction of first return maps. RESULTS: The frequency distribution of tic interval durations followed an inverse power law of temporal scaling. Spectral analyses similarly demonstrated that the spectral power density of tic interval duration scales inversely with frequency. ARIMA modeling suggested that the time series for tics are nonstationary as well as moving average processes. The first return maps demonstrated "burstlike" behavior and short-term periodicity in tics, and proved that successive tic intervals are not statistically independent. Graphic display of the time series confirmed shortterm periodicity, and in addition suggested the presence of period doubling. CONCLUSIONS: These findings are suggestive though not conclusive evidence for the presence of a fractal, deterministic, and possibly chaotic process in the tic time series. These analytic methods provide insight into the temporal features of tics that commonly are described clinically (such as short-term bouts or bursting, and longer term waxing and waning), and they reveal certain important temporal features of tics that have not been clinically described. The methods may also prove useful in the improved characterization of tic symptom severity.     

Time, distance, and feature trade-offs in visual apparent motion.

A model of visual apparent motion is derived from 4 observations on path selection in ambiguous displays in which apparent motion of illuminated dots could, in principle, be perceived along many possible paths: (a) Whereas motion over each path is clearly visible when its stimulus is presented in isolation, motion is usually seen over only 1 path when 2 or more such stimuli are combined (competition). (b) Path selection is nearly independent of viewing distance (scale invariance). (c) At transition points between paths i and j (where apparent motion is equally likely to be perceived along i and j), the time t and distance d between successive points along the paths are described by a log linear d/t relationship. (d) When successive elements along a path differ in orientation or size, the perceived motion along this path is not necessarily weaker than motion along a path composed entirely of identical elements. The model is a form of strength theory in which the path with greatest strength becomes the dominant path. (27 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Abstraction of temporal attributes.

Four experiments demonstrated cross-modal transfer (CMT) of classification rules for temporal intervals. In Exp I, 20 male albino Norway rats learned a temporal discrimination between a 2- and an 8-sec signal in one modality (vision or audition). Results show positive transfer to a temporal discrimination between a 2- and an 8-sec signal in the other modality when the response rule was maintained, and negative transfer when the response rule was reversed. Exp II with 20 Ss demonstrated positive CMT in a temporal generalization procedure. Exp III demonstrated CMT of both duration and temporal location in a procedure in which 20 Ss were exposed to 3 successive signal durations. Exp IV demonstrated CMT of both duration and temporal order in a procedure in which 5 Ss were exposed to simultaneously presented signal durations, one auditory and one visual. It is concluded that rats can abstract temporal attributes from modality-specific aspects of a signal. (38 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Benefits and Limits of Explicit Counting for Discriminating Temporal Intervals.

Compares the benefits of using explicit counting in a temporal discrimination task under various marker-type conditions and shows the limits of this strategy. In Experiment 1, conditions with and without counting were compared for two implicit standard durations, .8 and 1.6 s, in connection with three markertype conditions, which were intervals marked by: 1) two brief auditory signals (Auditory-Auditory); 2) two brief visual signals (Visual-Visual); and 3) one auditory signal followed by a visual signal (Auditory-Visual). At .8 s, markertype differences are significant (best in audition, worse with a bimodal sequence), and remain present with an explicit counting strategy. At 1.6 s, explicit counting provides clear improvements of performance in all marker-type conditions and annihilates marker-related differences. Experiment 1 also suggests that standard deviation remains constant in the counting condition, while Experiment 2 shows that when standard intervals are extended, explicit counting does not totally prevent variance from increasing as duration becomes longer. The benefits of explicit counting in duration discrimination are argued to depend (1) on a reduction of variance in the memory process in the timing mechanism, and (2) on a change in the decisional process. (PsycINFO Database Record (c) 2010 APA, all rights reserved)