Stimulus Exposure Time Research Articles

Effect of facial stimuli exposure time on evaluation of facial attractiveness

Effect of facial stimuli exposure time on evaluation of facial attractiveness

Effects of Stimulus Exposure Time on Generalization of Mere Exposure Effect to Averaged Composite Faces

Effects of Stimulus Exposure Time on Generalization of Mere Exposure Effect to Averaged Composite Faces

Automatic evaluation of body-related words among young women: an experimental study

BackgroundPrevious research has demonstrated that exposure to images depicting the thin female ideal has negative effects on some females' levels of body dissatisfaction. Much of this research, however, has utilised relatively long stimulus exposure times; thereby focusing on effortful and conscious processing of body-related stimuli. Relatively little is known about the nature of females' affective responses to the textual components of body-related stimuli, especially when these stimuli are only briefly encountered. The primary aim of the current research was to determine whether young women automatically evaluate body-related words and whether these responses are associated with body image concerns, including self-reported levels of appearance schematicity, thin internalisation, body dissatisfaction, and dietary restraint.MethodsAn affective priming task was used to investigate whether females automatically evaluate body-related words, and whether this is associated with self-reported body image concerns. In a within-participants experimental design, the valence congruence of the prime and target pairs was manipulated. Participants selected body words as primes in Experiment 1 (N = 27), while normatively selected body words were primes in Experiment 2 (N = 50). Each prime was presented briefly, followed by a target word which participants judged as "good" or "bad". The dependent variable was response latency to the target.ResultsAutomatic evaluation was evident: responding to congruent pairs was faster than responding to incongruent pairs. Body image concerns were unrelated to automaticity.ConclusionsThe findings suggest that brief encounters with body words are likely to prompt automatic evaluation in all young women, and that this process proceeds unintentionally and efficiently, without conscious guidance.

Object-based attention with endogenous cuing and positional certainty

Previous studies have concluded that object-based attention does not always arise if attention is cued endogenously (Macquistan, 1997) or if the target location is known with certainty (Shomstein & Yantis, 2002). In the Experiments reported here, we found object-based attention even when the locations of the two targets were known with certainty due to presentation of an endogenous cue. However, object-based attention can be prevented by limiting the exposure time of the object stimuli. These findings provide additional evidence against a search prioritization account of object-based attention. They lead to a fuller view of the role of object boundaries in directing attention. Object-based attention is frequently used spontaneously, even when the object boundaries are irrelevant to the task. However, object segmentation is not necessary for all tasks, because attention can be allocated before the stimulus has been segregated into objects.

The Miiller-Lyer Illusion as a Tool for Schizophrenia Screening

The perceptual deficit hypothesis for schizophrenia is based on more general models of normal human visual perception, which have traditionally postulated that objects must compete for attention and processing space in the visual system. Recent evidence suggests that susceptibility of schizophrenics to the Müller-Lyer (ML) illusion may be a marker of vulnerability, detectable in prodromic patients, but disappearing with the progression of the illness. This illusion consists of overestimating the length of a straight line with converging arrowheads at the ends, while underestimating those with diverging arrowheads. Although the ML illusion has been shown to occur in touch as well as vision, it is not known whether abnormal contextual suppression extends to other sensory modalities in schizophrenics. Another challenge consists in verifying whether different visual parameters of the illusion which favor the magnocellular and parvocellular systems would have diverse ML illusion effects in schizophrenia. In this review we present data showing the degree of illusion in capuchin monkeys (Cebus spp.), a possible animal model for schizophrenia. To this end, a computer program was developed to conduct experiments in humans and non-human primates, allowing the display of illusory figures, manipulation of the stimuli's exposure time, interval between stimuli and number of trials. In the non-primate experiments, the visual illusion test based on achromatic ML illusion figures indicated the presence of the ML illusory effect in 10 capuchin monkeys. These results suggest that Cebus might be a good model for the experimental study of schizophrenia.

Adaptation duration affects the spatial selectivity of facial aftereffects

Adaptation processes in human early visual cortical areas are sensitive to the exposure time of the adaptor stimulus. Here we investigated the effect of adaptation duration at the higher, shape-specific stages of visual processing using facial adaptation. It was found that long-term (5 s) adaptation evokes facial aftereffects consisting of a position invariant as well as a position-specific component. As a result of adaptation to a female face, test faces were judged more masculine when they were displayed in the same location as the female adaptor face, as compared to that when they were presented in the opposite visual hemifield. However, aftereffects evoked by short-term (500 ms) adaptation were found to be entirely position invariant. In accordance with these behavioral results, we found that the adaptation effects, measured on the amplitude of the N170 ERP component consisted of a position-specific component only after long-term, but not after short-term adaptation conditions. These results suggest that both short and long exposure to a face stimulus leads to adaptation of position invariant face-selective processes, whereas adaptation of position-specific neural mechanisms of face processing requires long-term adaptation. Our findings imply that manipulating adaptation duration provides an opportunity to specifically adapt different neural processes of shape-specific coding and to investigate their stimulus selectivity.

Acute effects of vibration on thermal perception thresholds

This study focuses on the acute effects of vibration and how vibrations influence the measures of the thermal perception thresholds during different vibration magnitudes, frequencies, and durations. The fingers of ten healthy subjects, five males and five females, were exposed to vibration under 16 conditions with a combination of different frequency, intensity and exposure time. The vibration frequency was 31.5 and 125 Hz and exposure lasted between 2 and 16 min. The energy-equivalent frequency weighted acceleration, according to ISO 5349-1, for the experimental time of 16 min was 2.5 or 5.0 m/s(2) (r.m.s.), corresponding to a 8-h equivalent acceleration, A(8) of 0.46 and 0.92 m/s(2), respectively. A measure of the thermal perception of cold and warmth was conducted before the different exposures to vibration. Immediately after the vibration exposure the acute effect was measured continuously on the exposed index finger for the first 75 s, followed by 30 s of measures at every minute for a maximum of 10 min. If the subject's thermal thresholds had not recovered, the measures continued for a maximum of 30 min with measurements taken every 5 min. For all experimental conditions and 30 s after exposure, the mean changes of the thresholds compared with the pre-test were found to be 0.05 and -0.67 degrees C for the warmth and cold thresholds, respectively. The effect of the vibration exposure was only significant on the cold threshold and only for the first minute after exposure when the threshold was decreased. The warmth threshold was not significantly affected at all. The frequency and the exposure time of the vibration stimuli had no significant influence on the perception thresholds for the sensation of cold or warmth. Increased equivalent frequency weighted acceleration resulted in a significant decrease of the subjects' cold threshold, not the warmth. The thresholds were unaffected when changes in the vibration magnitude were expressed as the frequency weighted acceleration or the unweighted acceleration. When testing for the thermotactile thresholds, exposure to vibration on the day of a test might influence the results. Until further knowledge is obtained the previous praxis of 2 h avoidance of vibration exposure before assessment is recommended.

Lateral Interactions and Speed of Information Processing in Highly Functioning Multiple Sclerosis Patients

Visual impairment is a common feature of multiple sclerosis. The aim of this study was to investigate lateral interactions in the visual cortex of highly functioning patients with multiple sclerosis and to compare that with basic visual and neuropsychologic functions. Twenty-two young, visually unimpaired multiple sclerosis patients with minimal symptoms (Expanded Disability Status Scale <2) and 30 healthy controls subjects participated in the study. Lateral interactions were investigated with the flanker task, during which participants were asked to detect the orientation of a low-contrast Gabor patch (vertical or horizontal), flanked with 2 collinear or orthogonal Gabor patches. Stimulus exposure time was 40, 60, 80, and 100 ms. Digit span forward/backward, digit symbol, verbal fluency, and California Verbal Learning Test procedures were used for background neuropsychologic assessment. Results revealed that patients with multiple sclerosis showed intact visual contrast sensitivity and neuropsychologic functions, whereas orientation detection in the orthogonal condition was significantly impaired. At 40-ms exposure time, collinear flankers facilitated the orientation detection performance of the patients resulting in normal performance. In conclusion, the detection of briefly presented, low-contrast visual stimuli was selectively impaired in multiple sclerosis. Lateral interactions between target and flankers robustly facilitated target detection in the patient group.

Rate of Learning and Asymptotic Performance in an Automatization Task and the Relation to Reading

In the present study, direct evidence was sought linking cognitive automatic processing with reading in the general adult population. Reading speed on single-task performance and dual-task performance were compared. A total of 18 adults without dyslexia participated (7 men and 11 women, age M=25.3 yr., SD=2.7). Participants initially were trained in single-task mode on two types of tasks. The first was a central alphanumeric equation task (true or false), which comprised 3 subtests of increasing difficulty, ranging from an easily automated task to a varied and unpredictable mathematical operation. The second task was a peripheral pattern subitization task for which stimulus exposure time was related to performance. Finally, participants received dual-task training, which required simultaneous processing of both tasks. Slower reading speed was significantly related to rate of learning and speed of performance on predictable alphanumeric operations in dual-task conditions. There was no effect of reading speed on performance in the varied alphanumeric task. Faster readers were no better than slower readers on the pattern-subitization task. These findings suggest that faster readers automatized the predictable alphanumeric task more rapidly than slower readers and hence were better able to cope with the dual-task condition.

Early aesthetic choices: Infant preferences for attractive premature infant faces

Previous studies have shown that when newborn and young infants are shown attractive and unattractive adult faces they will look longer at the attractive faces. Three studies with infants ranging from 5 months to 15 months were conducted to examine whether this attractiveness effect holds for infants looking at infant faces. A standard preferential looking technique was used in which infants were shown pairs of colour slides of upright (Experiments 1 and 2, n = 16) or inverted (Experiment 3, n = 16) infant faces previously rated by adults for attractiveness. Although Experiment 1 did not reveal an attractiveness effect, this effect did become manifest in Experiment 2 after increasing stimulus exposure time and replacing three of the original stimulus faces. The attractiveness effect was lost when faces were presented upside down. Findings are discussed in relation to the feature-based vs. configural processing debate in the face processing literature and in relation to the notion that attractiveness is based on presexual maturity rather than “cuteness”.

Automatic mimicry reactions as related to differences in emotional empathy.

The hypotheses of this investigation were derived by conceiving of automatic mimicking as a component of emotional empathy. Differences between subjects high and low in emotional empathy were investigated. The parameters compared were facial mimicry reactions, as represented by electromyographic (EMG) activity when subjects were exposed to pictures of angry or happy faces, and the degree of correspondence between subjects' facial EMG reactions and their self-reported feelings. The comparisons were made at different stimulus exposure times in order to elicit reactions at different levels of information processing. The high-empathy subjects were found to have a higher degree of mimicking behavior than the low-empathy subjects, a difference that emerged at short exposure times (17-40 ms) that represented automatic reactions. The low-empathy subjects tended already at short exposure times (17-40 ms) to show inverse zygomaticus muscle reactions, namely "smiling" when exposed to an angry face. The high-empathy group was characterized by a significantly higher correspondence between facial expressions and self-reported feelings. No differences were found between the high- and low-empathy subjects in their verbally reported feelings when presented a happy or an angry face. Thus, the differences between the groups in emotional empathy appeared to be related to differences in automatic somatic reactions to facial stimuli rather than to differences in their conscious interpretation of the emotional situation.

The effects of dot density and motion coherence on perceptual fading of a target in noise.

A peripherally presented target embedded in dynamic texture perceptually disappears (or 'fills-in') after around 10 s of steady fixation. This phenomenon was investigated for a target containing moving dots. The effects of manipulating the coherence of the motion within the target and the density of dots across the whole screen were explored. Coherence thresholds for the detection of a target at different dot densities were recorded for comparison. Fading occurred faster as either motion coherence or dot density was reduced. Coherence thresholds for target detection were unaffected by manipulations of dot density. There appeared to be no relationship between the stimulus exposure time needed for fading and the coherence threshold for detection of a target. The results suggest that the time taken for a target to fade is not a simple function of its motion detection threshold.

Rod-cone color mixture: effect of size and exposure time.

Chromaticity coordinates of monochromatic lights were obtained 8 deg extrafoveally at a retinal illumination of 50 photopic td during the cone-plateau period and also with the subject in a dark-adapted state, while size and exposure time of the test field were varied. Unexpectedly, we found that for the dark-adapted condition the points representing the chromaticity matches of the spectral lights generally moved away from the achromatic point in the chromaticity diagram when size or exposure time of the test stimulus was increased. Furthermore, the chromaticity shift toward the achromatic point, obtained between the cone-plateau period and the dark-adapted state (i.e., with rod intrusion), tended to decrease with these two test parameters. In fact, when size and exposure time both were at the maximum level investigated (7 deg, 500 ms), there was no measurable shift in chromaticity with rod intrusion. Our results suggest that the cone system may become progressively more effective in suppressing the rod system as an effect of both size and exposure time.

An examination of resource-based and fit-based theories of stereotyping under cognitive load and fit

Should stereotyping be characterised as an act of cognitive miserliness of one of rational meaning-seeking? This paper uses a cognitive load paradigm to investigate the adequacy of popular resource-based explanations of stereotyping in comparison to an alternative fit-based or meaning-based explanation. In Experiment 1, load was increased by means of concurrent tasks within a highly fitting context (where targets generally behaved in a stereotype-consistent fashion). A linear decrease in stereotyping resulted as measured by category confusions on a who-said what recognition task (Taylor, Fiske, Etcoff & Ruderman, 1978). This outcome is inconsistent with a resource-based analysis of stereotyping. Experiment 2 manipulated load as stimulus exposure time. Although load was successfully imposed in this second experiment, stereotyping neither increased nor decreased as a function of load. The concept of cognitive load and the importance of fit for the analysis of stereotyping are discussed. Copyright © 1999 John Wiley & Sons, Ltd.

Impaired Acquisition and Rapid Forgetting of Patterned Visual Stimuli in Alzheimer's Disease

Whether or not rate of forgetting is accelerated in Alzheimer's disease (AD) is controversial. This study examined recognition of visual patterns in patients with AD and in controls at 10 min relative to a learning baseline measured after a 10-s delay (delayed recognition ratio, DRR). Comparable baseline performances were attained in the two groups by manipulating stimulus exposure times. Comparisons between 25 AD and 48 age-matched controls demonstrated lower DRR in AD when initial recognition, which was statistically worse in AD, was covariated. DRR was also lower in an analysis of subgroups closely matched on initial performance. The findings suggest that forgetting is accelerated in AD because multiple aspects of memory processing, including storage, are impaired.

Shape priming in a complex visual search task

Shape priming was studied in four experiments comprising a complex search task in which subjects searched for a target shape presented among three distractors and reported the location of the target. Localization performance improved as a function of the duration of stimulus exposure and prime lead time. The efficiency of shape primes in improving performance decreased when lateral masks were presented near the target. Generally, both preprimes and simultaneous primes improved localization accuracy. With laterally masked stimuli, the preprimes and simultaneous primes were equally effective; when neighboring mask items were absent, the effect of preprimes was more pronounced. The results suggest that different strategies were used in the preprime and in the simultaneous-prime conditions.

Stimulation parameters for automatic examination of color vision

We have developed a polyvalent computer controlled instrument, which uses the "two equation method" (Rayleigh and Moreland equations) to measure human colour vision. This "colorimeter" (or anomaloscope) was used to determine the influence of some important stimulation parameters. The influence of stimulus exposure time, observation field size, absolute stimulus luminance, saturation and luminance mismatches between mixture and reference stimuli were measured on our computer controlled colorimeter. All subjects were normal observers. 1) An exposure time of 2s was found to be optimal for clinical work. 2) The Moreland equation on a 7 degrees observation field yields results in which population variability is comparable to a Rayleigh equation on a 2 degrees field. 3) A retinal illuminance between 40 and 1000 trolands can be used for automated Moreland matches. 4) The saturation of the reference field for the Moreland match can be preset to a fixed value. 5) It is important to vary automatically the radiance of the reference field to provide an approximate luminance match as the ratio of primaries in the mixture field is changed. These measurements allows us to determine optimal conditions for automated colour vision examinations and to make recommendations for an international standard.

The Simon effect occurs relative to the direction of an attention shift.

We investigated whether the Simon effect depends on the orienting of attention. In Experiment 1, participants were required to execute left-right discriminative responses to 2 patterns that were presented to the left or right of fixation. The 2 patterns were similar, and the discrimination was difficult. A letter at fixation signaled whether the current trial was a catch trial. The results showed a reversal of the Simon effect. That is, spatially noncorresponding responses were faster than spatially corresponding responses. In Experiment 2, the discrimination of the relevant stimulus attribute was easy. In Experiment 3, the discrimination of the relevant stimulus attribute was difficult, but the stimulus exposure time was long. In either experiment, the regular Simon effect was reinstated. In Experiment 4, the letter that signaled a catch trial appeared to the left or right of the imperative stimulus. The Simon effect occurred relative to the position of the letter.

Enhanced expression of transforming growth factor β1 in rat thyroid hyperplasia is thyrotropin induced and time dependent

Forty-three 8-week-old male Wistar rats were studied to evaluate temporal changes of transforming growth factor beta1, (TGF-beta1) mRNA levels in thyroid tissue during pharmacologically induced goiter. Four rats were treated with purified bovine thyrotropin (TSH; Ambinon, 2 mU/day sc) for 7 days before being sacrificed. Thirty-one were treated with propylthiouracil (PTU), added to their drinking water at a concentration of 0.2 g%, and subsequently were sacrificed as follows: five after 1 week (PTU-1): five after 2 weeks (PTU-2); five after 4 weeks (PTU-4); five after 8 weeks (PTU-8); five after 12 weeks (PTU-12). In six rats, after 12 weeks of treatment. PTU was withdrawn for 2 months and subsequently started again in three rats which were sacrificed after 2 weeks (PTU-R); the remaining three rats were sacrificed without any further treatment (PTU-R control). Eight rats (control rats) were never treated and served as controls. After sacrifice, blood was drawn for determination of total thyroxine and the thyroid was excised and subdivided into two lobes. Northern analysis for TGF-beta1 was performed in one lobe. while histological and immunohistochemical studies were performed in the other lobe. Gene expression of TGF-beta1 was induced in TSH- and PTU-treated rats. In TSH-treated rats TGF-beta1 gene expression was less detectable than in PTU-treated rats, where it became evident after 2 weeks and remained through weeks 4-8. Gene expression of TGF-beta1 wits also seen in PTU-R rats, but not in the control and in the PTU-R control. Immunohistochemical analysis showed a different presence and location for the TGF-beta1 protein, which appears to be dependent on the time of exposure to mitogenic stimulus. In conclusion, TGF-beta1 is produced in response to both a direct (TSH by itself) and indirect (TSH induced by PTU-induced hypothyroidism) cellular proliferative stimulus and is not linked to an adaptative phenomenon secondary to hypothyroidism. The immunohistochemical location of TGF-beta1 within the thyrocytes is influenced by mitogen exposure time. A TGF-beta1 immunohistochemical evaluation may be important to define exposure time and activity of goitrogenic stimuli.

Stimulus exposure time and perceptual memory.

The recent explosion of research on implicit memory has facilitated the examination of perceptual and conceptual processes in the encoding of information. Nevertheless, stimulus exposure time--the amount of time that a stimulus is physically available to a perceiver's scrutiny--has received little attention. In the present paper, we examine the effect of stimulus exposure time on three implicit memory measures (word-fragment completion, perceptual identification, and general knowledge) and two explicit memory measures (graphemic cued recall and semantic cued recall). In Experiment 1, we demonstrated that increases in exposure time lead to increases in implicit perceptual memory, but not to implicit conceptual memory, when the encoding task focuses on perceptual features of the stimulus. We replicated this effect in Experiment 2 and demonstrated that increases in exposure time lead to increases in perceptual and conceptual memory when the measures are explicit. Thus, the current experiments demonstrate that manipulations of exposure time lead to dissociations in implicit, but not explicit, memory.