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On the perception of time during prolonged temporal isolation.

UNLABELLED: In an underground isolation unit, 42 subjects were living singly for time spans of at least 7 days up to more than a month. Except three who were entrained to 24 h by an externally controlled light-dark cycle (LD), subjects had no time cues and developed free-running circadian rhythms either in self-selected LD-cycles or in constant illumination. Each subject had to give a signal whenever he thought that 1 h had passed. In addition, 30 subjects produced short-time intervals within the range from 10 to 120 s. RESULTS: The 1-h estimates were longer than 1 h, and had a strong positive correlation with the duration of wakefulness alpha as well as with the length of the circadian cycle. The short time estimates were equally distributed between under- and over-estimation of the required interval, and they were neither correlated with the 1-h estimates nor with alpha. It is concluded that long and short time estimates are based on different mechanisms.

Adolescent

Effect of density and environmental noise on perception of time, the situation, oneself and others.

The effects of density, intrusion of one's personal space, sex of subject, group composition, and environmental noise on the perception of time, the situation, oneself and others were investigated in this study. Generally, the results indicated that (1) both density and the intrusion of personal space concurrently affect the perception of crowding, (2) the physical factors interacted with the social and personal factors to affect the perception of several aspects of the situation, and (3) the environmental noise did not, for the most part, affect the perception of the situation.

Crowding

Facilitation of stereopsis from a large disparity random-dot stereogram by various monocular features: further findings (a short note).

This experiment examined the effects of adding five different kinds of prominent monocular features to a large-disparity random-dot stereogram. It was found that features which enclosed the disparate area produced the shortest initial perception times for fusion. The longer initial perception times for stimuli containing features without this enclosing property are explained in terms of less-helpful guidance of saccadic eye movements prior to the establishment of fusion. Subsequent reductions in perception times for these latter stimuli could be due to perceptual learning within the eye movement control system.

Depth Perception

Ratio judgments of empty durations with numeric scales.

A study is reported on the perception of empty time intervals marked by auditory signals. Nakajima's supplement hypothesis, which states that the subjective duration of a subjectively empty time interval is proportional to its physical duration plus a constant of approximately 80 ms, was examined quantitatively. Although this hypothesis has been used to explain various general aspects of time perception, from a global viewpoint, it has lacked the quantitative data necessary to describe the shape of the psychophysical functions mathematically. In the present study, subjects used two positive numbers to estimate the subjective ratio (m:n) between the durations of two serial or separate empty intervals. The psychophysical functions for empty durations 50-600 ms long could be approximated by a straight line with a positive gamma-intercept, as predicted by the hypothesis. The effective range of the hypothesis could be extended to approximately 1200 ms. A power function (without any modifications) also gave good approximations. The reliability and validity of the supplement hypothesis are discussed.

Adult

Effects of atropine on operant test battery performance in rhesus monkeys.

The acute behavioral effects of atropine sulfate were assessed using a battery of complex food-reinforced operant tasks that included: temporal response differentiation (TRD, n = 7); delayed matching-to-sample (DMTS, n = 6), progressive ratio (PR, n = 8), incremental repeated acquisition (IRA, n = 8), and conditioned position responding (CPR, n = 8). Performance in these tasks is thought to depend primarily upon specific brain functions such as time perception, short-term memory and attention, motivation, learning, and color and position discrimination, respectively. Atropine sulfate (0.01-0.56 mg/kg iv), given 15-min pretesting, produced significant dose-dependent decreases in the number of reinforcers obtained in all tasks. Response rates decreased significantly at greater than or equal to 0.03 mg/kg for the learning and discrimination tasks, at greater than or equal to 0.10 mg/kg for the motivation and short-term memory and attention tasks, and at greater than or equal to 0.30 mg/kg for the time perception task. Response accuracies were significantly decreased at doses greater than or equal to 0.10 mg/kg for the learning, discrimination, and short-term memory and attention tasks, and at greater than or equal to 0.30 mg/kg for the time perception task. Thus, the order of task sensitivity to any disruption by atropine is learning = color and position discrimination greater than time perception = short-term memory and attention = motivation (IRA = CPR greater than TRD = DMTS = PR). Thus in monkeys, the rates of responding in operant tasks designed to model learning and color and position discrimination were the most sensitive measures to atropine's behavioral effects. Accuracy in these same task was also disrupted but at higher doses. These data support the hypothesis that cholinergic systems play a greater role in the speed (but not accuracy) of performance of our learning and discrimination tasks compared to all other tasks. Accuracy of responding in these and the short-term memory task, all of which involve the use of lights as visual stimuli, was more sensitive to disruption by atropine than those tasks which did not utilize such strong visual stimuli.

Animals