Duration Of Stimulus Presentation Research Articles

Dynamical use of different sources of information in heading judgments from retinal flow.

The optic flow arising in the eyes of an observer during self-motion is influenced by the occurrence of eye movements. The determination of heading during eye movements may be based on the pattern of retinal image motion (the retinal flow) or on an additional use of an extraretinal eye-movement signal. Previous research has presented support for either of these hypotheses, depending on the movement geometry and the layout of the visual scene. A special situation in which all previous studies unequivocally have agreed that an extra-retinal signal is required occurs when the visual scene consists of a single frontoparallel plane. In this situation eye movements shift the center of expansion on the retina to a location that does not correspond to the direction of self-movement. Without extraretinal input, human observers confuse the center of expansion with their heading and show a systematical heading estimation error. We reexamined and further investigated this situation. We presented retinal flow stimuli on a large projection screen in the absence of extra-retinal input and varied stimulus size, presentation duration, and orientation of the plane. In contrast to previous studies we found that in the case of a perpendicular approach toward the plane, heading judgments can be accurate. Accurate judgments were observed when the field of view was large (90 degrees x 90 degrees) and the stimulus duration was short (< or = 0.5 s). For a small field of view or a prolonged stimulus presentation, a systematic and previously described error appeared that is related to the radial structure of the flow field and the location of the center of expansion. An oblique approach toward the plane results in an ambiguous flow field with two mathematically possible solutions for heading. In this situation, when the stimulus duration was short, subjects reported a perceived heading midway between these two solutions. For longer flow sequences, subjects again chose the center of expansion. Our results suggest a dynamical change in the analysis or interpretation of retinal flow during heading perception.

Information reduction during skill acquisition: The influence of task instruction.

H. Haider and P. A. Frensch's (1996) information reduction hypothesis holds that with practice, people leam to distinguish task-relevant from task-redundant information and to ignore task-irrelevant information. In 2 experiments, the authors examined whether degree of information reduction can be directly affected by task instruction. Participants verified alphabetic arithmetic tasks containing task-relevant and task-irrelevant information. Participants were asked to optimize their accuracy or their speed of performance throughout the entire experiment or to optimize accuracy for half of the experiment and speed for the other half of the experiment or vice versa (first speed, then accuracy). In addition, time duration of stimulus presentation under speed instruction was systematically reduced over practice in Experiment 2. Results showed that amount of information reduction was affected by instructions, suggesting that the process of information reduction is at least partially under voluntary control. Think of two people, one an experienced user of computer software and the other an inexperienced user, both trying to install some new computer software. During the installation process, a number of messages are displayed on the screen, some of which need to be attended to and some of which may be safely ignored. Whereas the inexperienced user is likely to thoroughly read through all messages displayed on the screen, the skilled user very likely pays attention

A Comparison of Sequential and Spatial Displays in a Complex Monitoring Task

A sequential or RAP COM (rapid communication) display was compared with a more conventional spatial display as participants monitored dynamically changing sets of three-digit numbers and responded to occasional target stimuli. In an effort to equate the stimulus-response compatibility of the two displays, we had participants respond to the targets with a chord keyboard in Experiment 1 and vocally in Experiment 2. We examined the influence of display duration on performance with the RAP COM and spatial formats by presenting stimuli at three different durations (400, 800, and 1200 ms). The influence of practice on performance with the RAP COM and spatial displays was also investigated. Participants responded to targets more quickly in the RAP COM than in the spatial displays at each of the three presentation durations and across more than 2000 trials of practice. Accuracy was influenced by the display presentation duration. Accuracy was higher for the RAP COM than for the spatial display at the 800-ms stimulus presentation duration in Experiment 1 and at the 800- and 1200-ms presentation durations in Experiment 2. The results are discussed in terms of the potential utility of RAP COM displays for complex, real-world systems.

A Comparison of Sequential and Spatial Displays in a Complex Monitoring Task

A sequential or RAP COM display was compared to a more conventional spatial display as subjects monitored dynamically changing sets of numbers and responded to occasional target stimuli. In an effort to equate the stimulus-response compatibility of the two displays subjects responded to the targets with a chord keyboard. We examined the influence of display duration on the performance with the RAP COM and spatial formats by presenting the stimuli at three different durations, 400, 800 and 1200 msec. The influence of practice on performance with the RAP COM and spatial displays was also investigated. Targets were responded to more quickly in the RAP COM than in the spatial displays at each of the three presentation durations and across over 2000 trials of practice. Accuracy was influenced by the display presentation duration. Accuracy was higher for the RAP COM than the spatial display at the 800 msec stimulus presentation duration. Accuracy was statistically equivalent for the RAP COM and spatial displays at the 400 and 1200 msec display durations, although there was a trend for lower accuracy for the RAP COM display at the faster presentation duration. Interestingly, the lower accuracy for the RAP COM display format at the 400 msec presentation duration appears to be due to illusory conjunctions. Our results will be discussed in terms of the utility of sequential or RAP COM displays in complex, real-world settings.

Response-independent habituation of the orienting response in the preweanling rat

The effect of pattern of stimulus presentation on habituation of the cardiac component of the orienting response to an auditory stimulus was investigated in four experiments. The duration of stimulus presentation was held constant, but some animals were given six 10-sec stimulus presentations and others were given a single 60-sec stimulus. During the first 10 sec of the auditory stimulus, heart rate (HR) decreased approximately 40 beats per minute (bpm) in both groups, but during subsequent 10-sec epochs, the changes in HR were markedly different in the two groups. For those animals given a single 60-sec stimulus, the cardiac orienting response did not habituate; that is, HR either continued to decrease or remained approximately 40 bpm below baseline. In contrast, those animals given six 10-sec stimulus presentations showed smaller decreases in HR with each successive stimulus presentation, and after approximately four presentations, no detectable change in HR was observed. Despite these dramatic differences in habituation of the cardiac component of the orienting response, neither group oriented to the auditory stimulus when it was presented again following a short retention interval. Moreover, with increasing retention intervals, both groups showed the same forgetting function (reappearance of the orienting response). The implications of these findings for theories of the orienting response as well as theories of habituation are discussed.

Stimulus- and feeder-directed behavior in a long-box: Effect of fixed versus variable time schedules of food presentation

Two groups of 6 pigeons were exposed to either a fixed-time (FT) or a variable-time (VT) schedule of response-independent food presentation. The interval between two successive food presentations (food-food [FF] interval) was either 20 or 40 sec. The duration of stimulus presentation (stimulus-food [SF] interval) was varied relative to the FF interval. All subjects were exposed to different information ratios (IRs; IR = SF/FF; IR = 1.00, 0.50, 0.15). To study the relative contribution of sign- and goal-tracking behavior to keypecking observed in standard autoshaping procedures, pigeons were autoshaped in a long-box. In the long-box, the stimulus key and the feeder are located 60 cm apart. Stimuli were always presented at one end of the box, and food was presented at the other end. Locomotor behavior and keypecks were recorded. Pigeons engaged in sign-tracking behavior when IR = 0.15, but only when presentation of the food was unpredictable on the basis of other variables (e.g., the passage of time since the last food presentation, as in FT schedules). In the case of FT schedules, subjects engaged in feeder-directed activities. No effects of varying the FF interval were found. Keypecking was observed only when the SF interval was short (IR = 0.15) and food was presented on a VT schedule.

Patterns of Looking Behavior in Full-Term and Low Birth Weight Infants at 40 Weeks Post-Conceptional Age

Given the usefulness of visual behavior as an assessment method in older infants, a simple method of visual behavioral evaluation applicable in clinical settings was utilized to gather descriptive data on 42 infants at term. Using an "infant control" method for determining the duration of stimulus presentation, a series of four patterned targets was presented to 25 healthy full-term (FT) and 17 low birth weight (LBW) infants at 40 weeks postconceptional age. Infants were examined in their nursery cribs, and each stimulus was presented until the infant reached a criterion of a 50% or greater decrement in looking time. LBW infants looked for longer time periods, without pause, than FT infants; LBW mean trial length was twice that of FTs. Although total looking time was longer for the LBW group, LBW infants took twice the length of time as FTs to reach the decrement criterion for the first target and thus viewed fewer targets than FT infants. Despite the longer looking of LBW infants, only 41%, as compared to 56% of the FT group, showed an increase in looking time when a new stimulus was presented. The quality of LBW infants' visual behavior was more often marked by long, continuous looking at the same pattern, in contrast to shorter, more discrete and rapidly decrementing looks by the FT newborn. While there was a large variability within groups, the differential patterns of visual behavior are considered likely to reflect variations in processing of information, possibly associated with differences in integrity or maturation of the visual system.

Role of cerebral hemispheric processing in the visual half-field stimulus-response compatibility effect.

Two experiments were conducted to test theories of the stimulus-response (S-R) compatibility effect. Stimuli presented above and below a fixation point in the left and right visual field signaled choice responses in the midsagittal plane. Even though the duration of stimulus presentation in Experiment 1 was sufficiently brief, such that the possibility of eye movements was precluded, a visual half-field S-R compatibility effect was still obtained. That such an effect is found when it can be adequately specified to which hemisphere stimulus information is presented suggests that an explanation in terms of cerebral laterality factors be considered. The second experiment employed arbitrary symbols to represent the spatial property of stimuli used in prior experiments, and a similar pattern of results was obtained. These results are discussed in terms of a functional view of cerebral organization.

Effects of response-contingent clock stimuli on behavior maintained by intravenous codeine in the rhesus monkey

Response-contingent brief presentations of clock stimuli differentially correlated with food availability altered rates of codeine-maintained lever pressing. Rhesus monkeys performed under a two lever multiple schedule: Multiple fixed interval clock 5 min variable interval 2 min. Different colored lights were presented during successive 75 sec periods of the fixed-interval clock component. Lever pressing under the FI Clock schedule was maintained by presentation of 1 g Noyes pellets, and lever pressing under the VI schedule by 0.05 mg/kg infusions of codeine PO 4. Characteristic schedule-controlled performance developed in both schedule components. When the clock stimulus from the first or the final period of the FI Clock schedule was presented contigent upon completion of a short fixed ratio of responses during the variable-interval schedule component, the first clock stimulus decreased and the final clock stimulus increased rates of codeine-maintained lever pressing. Neither the first nor the final clock stimulus altered the frequency of codeine injection. The effect of each clock stimulus was accentuated by increasing the duration of stimulus presentation and by decreasing the response requirement for stimulus illumination. These rate-altering effects of the clock stimuli were most pronounced when different reinforcers were presented in the two components of the multiple schedule when either food or intravenous codeine injection was available under both components of the multiple schedule, response-contingent clock stimulus presentation did not alter response rates under the VI schedule.

Effect of stimulus presentation duration on gustatory reaction time

Human simple reaction time to 3 sec and brief (200 and 400 msec) flow durations of aqueous 500 mM NaCl to the anterior dorsal tongue surface was measured for fifteen participants. Overall reaction time was 403 ± 30 msec (median ± 99% standard error of the median confidence interval). No statistically significant difference in reaction time as a function of flow duration was found. We conclude that 200 msec is ⩾ minimum human taste input time. This suggests that the phasic components of the gustatory neural response are sufficient for some human taste judgments.

Role of the auditory cortex in recognition of synthesized vowels by dogs.

1. An auditory pattern of a stationary vowel, invariant relative to changes in certain parameters — the basic frequency, intensity, and duration of presentation (300-75 msec)-can be formed in intact dogs. Two formulas are sufficient for identification of the vowels [a] and [i]. 2. The auditory pattern of the vowels [a] and [i] is preserved after bilatal removal of the auditory projection cortex and it can be formed in animals after preliminary removal of the auditory cortex. 3. The identification of vowels by animals after preliminary removal of the auditory cortex is disturbed when the excessiveness of information contained in the stimuli is reduced (the number of formants is reduced and the duration of stimulus presentation is short-ened).

Primate information processing under sodium pentobarbital and chlorpromazine: Differential drug effects with tachistoscopically presented discriminative stimuli

Sodium pentobarbital and chlorpromazine were evaluated for the degree to which they differentially reduce the speed or efficiency with which sensory information can be processed. Rhesus monkeys were tested under comparable doses of sodium pentobarbital and CPZ on a visual discrimination problem with varying durations of tachistoscopically presented stimulus information. When unlimited stimulus information was available, no effects of the two drugs were observed at the doses used, but as the duration of stimulus presentation was progressively decreased, the effects of sodium pentobarbital became more severe, whereas CPZ did not differe from the saline control an any presentation duration. While previously published literature indicates that CPZ impairs performance by intermittantly blocking sensory input or transmission, the present data provide the first direct behavioral confirmation that barbiturates impair performance by retarding the rate at which sensory stimuli can be processed and utilized.

Duration of stimulus presentation and screening for perceptual disabilities.

This study examined the effects of increasing the stimulus-presentation time of a motion picture test for identifying perceptual disabilities in the performance of Ss in regular first and fourth grade classrooms and on a sample of Ss in special education classes who had been identified as having varying degrees of perceptual deficiencies. The length of stimulus presentation increased the total performance of Ss on the motion picture test but did not add to the value of the instrument as a screening device.

Sucrose preferences of hungry and thirsty rats as a function of duration of stimulus presentation.

Sucrose preferences of hungry and thirsty rats as a function of duration of stimulus presentation.

Effect of duration of stimulus presentation on the angular acceleration threshold.

Human oculogyral illusion thresholds determined on Ames Man-Carrying Rotation Device to establish stimulus duration effect on angular acceleration thresholds