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PubMed1996

Characterization of hydrotropism: the timing of perception and signal movement from the root cap in the agravitropic pea mutant ageotropum.

In this study, ageotropum pea mutant was used to determine the threshold time for perception of an osmotic stimulation in the root cap and the time requirement for transduction and transmission of the hydrotropic signal from the root cap to the elongation region. The threshold time for the perception of an osmotic stimulation was compared to current estimates of threshold times for graviperception in roots. The time required for transduction and transmission in the hydrotropic response of ageotropum was compared to the time requirement in the gravity response of Alaska pea roots. We determined that threshold time for perception of an osmotic stimulation in the root cap is very rapid, occurring in less than 2 min following the application of sorbitol to the root cap. Furthermore, a single 5 min exposure of sorbitol to the root cap fully induced a hydrotropic response. We also found that transduction and transmission of an osmotic stimulus requires 90-120 min for movement from the root cap to more basal tissues involved in differential growth leading to root curvature. The very rapid threshold time for perception of root hydrotropism is similar to those times reported for root gravitropism. However, the time required for the transduction and transmission of an osmotic stimulation from the root cap is significantly longer than the time required in gravitropism. These results suggest that there must exist some differences between root hydrotropism and gravitropism in either the rate or mechanisms of transduction and transmission of the tropistic signal from the root cap.

Gravitropism↗
PubMed1978

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↗
PubMed1976

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↗
PubMed2003

A right hemispheric frontocerebellar network for time discrimination of several hundreds of milliseconds.

Debate still surrounds the nature of the role of the dorsolateral prefrontal gyrus (DLPFC) in time perception. This region is frequently associated with working memory and is thus implicated as a so-called "accumulator" within a hypothesized internal clock model. However, we hypothesized that this region may have a more primary role in time perception. To test this hypothesis we used functional magnetic resonance imaging (fMRI) to examine the neural correlates of relatively pure time perception with a temporal discrimination task where intervals of 1 s had to be discriminated from those of 1.3, 1.4, and 1.5 s. Time perception in this particular time domain within the "perceived present" has not previously been investigated using fMRI. By using relatively short time periods to be discriminated and also contrasting activation with an order judgment task, we aimed to minimize the confounding aspects of sustained attention and working memory. In a group of 20 healthy right-handed adult males, neural activation associated with time discrimination was found in a predominantly right hemispheric network of right dorsolateral and inferior prefrontal cortices, right supplementary motor area, and left cerebellum. We conclude that right DLPFC, rather than having a purely working memory function, might be more centrally involved in time perception than previously thought.

Adult↗
PubMed1999

Perception of time: delay of estimation under auditory and visual tasks with type-A measures.

The perception of time is likely to be lengthened when estimates of duration are delayed rather than given immediately as reported by Vitulli and Crimmins in 1999. The present study sought boundary conditions for this robust effect. A multivariate analysis of variance showed a reliable main effect for delay of estimation, yet comparisons between auditory versus visual short-term memory tasks showed no differences in time estimations. The analysis showed weak interactions between sex and delay of estimation and between sex and delay of estimation on Jenkins Activity Survey-Job Involvement scores.

Auditory Perception↗
PubMed2002

Auditory chronostasis: hanging on the telephone.

The perception of time can be illusory: we have all waited anxiously for important seconds to tick away slowly at the end of a football game and have experienced the truth of the adage "time flies when you're having fun." One illusion of time experience that has recently been investigated, the apparent slowing of the movement of the second hand on the clock when one first looks at it, has been termed "chronostasis," and it has been suggested that the effect is unique to vision and is dependent on eye movements. We sought to test whether the effect is really unique to vision or whether it can also be produced with auditory stimuli. Subjects were asked to judge the length of a silent gap between two tones presented through headphones. When the tones were presented to one ear, subjects judged the duration of the gap veridically. When subjects were required to shift concentration from one ear to the other, however, the judgement of time showed that the auditory system is also susceptible to chronostasis. We suggest that this generalization of chronostasis to another sensory system is consistent with theories of time perception that emphasize a single, multimodal clock for duration estimation rather than a mechanism that is dependent on motor acts.

Auditory Perception↗
PubMed1994

Managing the perceptions of patient wait time.

Patients' perception of waiting time in the dental office can greatly affect their satisfaction of service. Traditional approaches to managing patient perceptions of wait time are discussed, and some new strategies are explored.

Appointments and Schedules↗
PubMed2003

Accuracy of sleep perceptions among insomnia sufferers and normal sleepers.

OBJECTIVE: To examine the distribution, consistency, and correlates of sleep time perceptions in primary insomnia sufferers and normal sleepers across settings (laboratory and home). METHODS: Fifty-two middle-aged and older insomnia sufferers and 49 matched normal sleepers underwent multiple nights of laboratory and home polysomnography (PSG) and provided concurrent subjective estimates of their sleep. Descriptive statistics, cluster analyses, and inferential tests were used to examine the nature of sleep time perceptions, identify subgroups with distinctive patterns such as perceptions, and explore factors that may contribute to these subgroups' distinctive sleep perceptions. RESULTS: Consistent with previous studies, the insomnia sufferers, as a group, showed a greater tendency to underestimate the time they slept than did the normal sleepers, but the accuracy of sleep time perceptions varied widely within each sample. Correlational analyses showed that study participants in each sample showed a moderate level of consistency in how accurately they estimated sleep time across nights. Subsequent cluster analyses conducted to identify subgroups with distinctive patterns of sleep time perceptions yielded four subgroups within the insomnia sample and three subgroups within the normal sleeper sample. Although the sleep setting significantly affected sleep perceptions for one insomnia subgroup, both laboratory and home objective-subjective sleep comparisons provided similar impressions regarding the relative accuracy of each subgroup's nocturnal sleep/wake perceptions. Finally, varying patterns of subgroup differences were noted across several common psychometric measures. CONCLUSIONS: The underestimation of sleep time is not a generic characteristic that separates all insomnia sufferers from normal sleepers. Sleep setting, personality traits, and perhaps constitutional factors appear to influence perceptions of sleep and wake time duration.

Analysis of Variance↗
PubMed2002

Perception of timing is more context sensitive than sensorimotor synchronization.

In three experiments, the effects of contextual temporal variation on the perception of timing and on sensorimotor synchronization were examined. Experiment 1 showed that exposure to a variably timed auditory precursor sequence reduces the detectability of deviations from isochrony in a musical test sequence. By contrast, in Experiment 2 there was only a small and transient effect of identical precursor sequences on the variability of finger taps that were synchronized with a similar test sequence. Moreover, the precursor did not impede phase error correction following deviations from isochrony in the test sequence. Experiment 3 employed a within-subjects design that required simultaneous detection of irregularities in and synchronization with nonmusical auditory sequences. Precursor variability impaired only detection, not synchronization performance. These results suggest that perception of deviations from regularity engages context-sensitive tining processes, probably related to conscious awareness, that are not involved in sensorimotor synchronization.

Adult↗
PubMed1997

The development and evaluation of the hypertension temporal orientation (HTO) scale.

Temporal orientation is a multidimensional concept that describes the perception of time among individuals. Time perception is structured by life experiences and can vary depending upon the particular context involved. Whether a person is past-, present- or future-oriented has been shown to influence his/her approach and reaction to health situations. Because the management of hypertension is based on achieving some future health state, hypertension provides a context in which an individual's time perspective may be particularly influential. One purpose of this study was to develop and evaluate a scale to measure temporal orientation that was specific to hypertension, namely the hypertension temporal orientation (HTO) scale. Data were collected via telephone interviews with 300 people who had been diagnosed by a physician as having hypertension. Principal components factor analysis revealed three dimensions of hypertension temporal orientation: (1) a nonexperiential domain; (2) an experiential disease domain; and (3) an experiential treatment domain with coefficient alpha estimates of 0.76, 0.66, and 0.63, respectively. The HTO scale was significantly discriminant of African Americans and whites on the experiential treatment domain whereby African Americans were more present-oriented regarding the daily management (or treatment) of hypertension as compared to whites. Additional evidence for the validity of the HTO scale was found with temporal orientation group comparisons on health perceptions. The findings provide early support for the reliability and validity of the HTO scale for measuring temporal orientation among people with hypertension.

Adult↗
PubMed2001

From physical time to the first and second moments of psychological time.

After examination of the status of time in experimental psychology and a review of related major texts, 2 opposite approaches are presented in which time is either unified or fragmented. Unified time perception views, usually guided by Weber's law, are embodied in various models. After a brief review of old models and a description of the major contemporary models of time perception, views on fragmented time perception are presented as challenges for any unified time view. Fragmentation of psychological time emerges from (a) disruptions of the Weber function, which are caused by the types of interval presentation, by extensive practice, and by counting explicitly or not; and (b) modulations of time sensitivity and perceived duration by attention and interval structures. Weber's law is a useful guide for studying psychological time, but it is also reasonable to assume that more than one so-called central timekeeper could contribute to perceiving time.

Attention↗
PubMed1995

Perceptual latency and complex random-dot stereograms.

Naive observers of random-dot stereograms depicting complex surfaces often find that they require several tens of seconds before the impression of depth emerges. With practice, however, perception times often decrease markedly: perceptual learning occurs. Current explanations of these effects were assessed in two experiments. In the first experiment the perception times of naive observers for random-dot stereograms which depicted the same complex shape but contained different ranges of disparity were measured. In the second experiment the minimum times required by experienced observers to perceive a given complex shape in stereograms that contained different ranges of disparity were determined. Perception times for the naive observers were all very fast (<3 s) and showed no evidence of perceptual learning. There was no effect of disparity range on perception times in either experiment. It was found that very large-disparity (80 min arc) complex stereograms could be perceived quickly, even by naive observers. It is concluded that the long initial latencies previously reported are not due to surface complexity nor to the range of disparities present. Other factors. such as dot size, dot density, and the correlation of the stereo images, appear to be important determinants of efficient stereoscopic performance when viewing complex random-dot stereograms.

Depth Perception↗
PubMed2000

[Variable perception of time in inpatient geriatric care--how long is the present?].

Time and again a lack of staff in the field of people's nursing is discussed (chronic lack of nursing staff); this means that there are not enough people to do the available work) (1). However, the time factor is also an important sociological dimension in old people's stationary care. First of all, this article points out the time dimension throughout life. This is followed by people's varying perceptions of the present and the related upsets and misunderstandings. Hereby the contradictory abundance and limitation in time as felt by the elderly also becomes apparent. The old people's awareness of the dwindling remainder of their own lifespans conflicts with the seemingly endless time of each day that passes.

Activities of Daily Living↗
PubMed1988

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↗
PubMed1993

On dopaminergic modulation of temporal information processing.

Temporal processing of durations in the range of seconds or more (i.e. time estimation) is cognitively mediated, whereas processing of brief durations in the range of milliseconds (i.e. time perception) appears to be beyond cognitive control and based on neural counting mechanisms. Although there is some evidence from animal and human studies suggesting that the internal timing mechanism underlying time perception is modulated by the effective level of brain dopamine, the findings are not conclusive. Therefore, the effects of pharmacologically induced changes in D2 receptor activity on temporal information processing were evaluated. In a double-blind design, either 3 mg of haloperidol, 150 mg of remoxipride, or placebo were administered in a single oral dose. Performance on time estimation was significantly impaired by both haloperidol and remoxipride as compared with placebo. Both drugs obviously affected cognitive mechanisms underlying temporal processing of durations in the range of seconds. On the other hand, only haloperidol produced a significant decrease in performance on time perception as compared with placebo and remoxipride, whereas the remoxipride and placebo groups did not differ significantly. The differential effects of haloperidol and remoxipride on performance on time perception suggest that D2 receptor activity in the basal ganglia may play a critical role in timing of brief durations in the range of milliseconds.

Acoustic Stimulation↗
PubMed2001

Three days fast in sportsmen decreases physical work capacity but not strength or perception-reaction time.

This study investigates, in young nonobese healthy athletes, the consequences of a 3-day fast coupled, or not, to enhanced physical activity. Eight male subjects, aged 21+/-2 years, fasted for 3 days on two separate occasions, 4 weeks apart. On the first occasion, subjects continued their daily training activities. On the second occasion, a daily physical exercise program was added to these activities. Subjects were evaluated before and after 24 hours and 72 hours of fasting. Evaluation consisted of body composition, basal respiratory exchange ratio, plasma metabolic parameters, perception-reaction time (both simple and discriminant), hand grip strength, and physical work capacity at 170 beats per minute (PWC170). Fasting determined significant reductions in body weight, body fat, and muscle mass. These reductions were not affected by enhanced physical activity. Basal respiratory exchange ratio decreased with fasting but was not influenced by increased training activities. Fasting determined a significant decrease in blood glucose levels, while plasma proteins, urea, uric acid, and free fatty acids increased. Perception-reaction time and hand grip strength were unmodified during fasting. By contrast, PWC170 was significantly and progressively reduced during fasting, and this decrease was not reversed by an increase in training activities.

Adult↗
PubMedDate not supplied

Giving the older driver enough perception-reaction time.

Many types of behavior slow with age, and older drivers require more time to process information and make decisions. How greater response time requirements relate to the design of the highway environment and to features of new in-vehicle technologies is discussed. The design requirements for many different aspects of roadway geometrics and traffic control devices are based on design driver perception-reaction times. However, without knowing how much slower older drivers are than the design driver, it is difficult to determine whether they are adequately protected by current design practice and, if not, what the desired change in design should be. Attempts to address this have been hampered by the lack of directly relevant data, the situation-specific nature of certain findings, and the older driver's ability to compensate for declines in basic skills. Also discussed are the promise and problems of new in-vehicle technologies for providing the older driver with adequate time to act. These intelligent vehicle highway systems (IVHS) may speed navigational decision making and recognition of hazards and maneuver requirements. However, the possibility for interfering with quick responding also arises, and IVHS systems might disadvantage the older driver in other ways.

Aged↗