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PubMed2003

[Influence of body size on the electric current perception threshold].

Although the threshold for electric current perception is of great importance for safety considerations and safety regulations, important aspects remain unsolved, e.g. the role of age or body size. In the present study measurements of the perception threshold were performed in 790 persons aged between 18 and 82 years randomly selected from the general population. For the first time, the composition and size of the sample were selected such as to allow extrapolation to the general population. The results reveal not only statistically significant gender differences in the perception threshold but also statistically significant relationships between perception threshold and body size. The assumption that the differences in body size between men and women are responsible for the gender-specific difference in electric current perception threshold was not confirmed in this study.

Adolescent↗
PubMed2006

Perceptions and beliefs about body size, weight, and weight loss among obese African American women: a qualitative inquiry.

The purpose of this qualitative study was to explore perceptions and beliefs about body size, weight, and weight loss among obese African American women in order to form a design of weight loss intervention with this target population. Six focus groups were conducted at a community health clinic. Participants were predominantly middle-aged with a mean Body Mass Index of 40.3 +/- 9.2 kg/m(2). Findings suggest that participants (a) believe that people can be attractive and healthy at larger sizes; (b) still feel dissatisfied with their weight and self-conscious about their bodies; (c) emphasize eating behavior as the primary cause for weight gain; (d) view pregnancy, motherhood, and caregiving as major precursors to weight gain; (e) view health as the most important reason to lose weight; (f) have mixed experiences and expectations for social support for weight loss; and (g) prefer treatments that incorporate long-term lifestyle modification rather than fad diets or medication.

Adult↗
PubMed1997

Measures of perceived linear size, sagittal motion, and visual angle from optical expansions and contractions.

Using monocular observation, open-loop measurements were obtained of the perceptions of linear size, angular size, and sagittal motion associated with the terminal (largest or smallest) stimuli of repetitive optical expansions and contractions using 1-D or 2-D displays produced on a video monitor at a constant distance from the observer. The perceptions from these dynamic conditions were compared with those from static conditions in which the stimuli were of the same physical size and at the same physical distance as the terminal dynamic stimuli, but that were not part of the optical expansions or contractions. One result, as expected, was that the measures of perceived linear and angular size differed, but also, unexpectedly, some substantial errors were associated with the measures of perceived angular size. Another result was that the amount of size constancy was considerably less than was expected from the obtained amount of perceived motion in depth. Consistent with the latter result, it was found that the size-distance invariance hypothesis (SDIH), using the physical visual angles of the terminal stimuli, predicted only about half of the perceived motion in depth obtained with the dynamic changes. Using the obtained measures of perceived visual angles in the SDIH increased rather than decreased the error in predicting the amount of motion in depth as perceived. An additional experiment suggests that at least some of the error in the measurement of the perceived visual angle is a consequence of error in the perceived origin of the visual angles. The absence of the expected relation between size constancy and perceived motion in depth in the dynamic conditions is hypothesized to be due to cognitive processes associated with off-sized perceptions of the stimuli.

Depth Perception↗
PubMed1983

"Conservations" with a chimpanzee.

Two chimpanzees (Pan tryglodytes), Fanny and Jane, were presented with liquid and number conservation problems. One chimpanzee, Jane, was successful in solving both sets of problems in that she was not distracted by irrelevant transformations, being influenced only by changes in quantity. Her success appeared to be based on the ability to make inferences rather than on simple perceptual judgement of the final comparison. The results are compared and contrasted with those of Premack, in G. Woodruff, D. Premack, and K. Kennel [(1978). Conservation of liquid and solid quantity by the chimpanzee. Science, 202:99-994] and J. Mehler and T. G. Bever [(1967). Cognitive capacity of very young children. Science, 158:141-142; (1968). Quantification, conservation and nativism. Science, 162:979-981], and it is suggested that there may be a similarity of conservation development between chimpanzees and man.

Animals↗
PubMed1979

The responses of magno- and parvocellular cells of the monkey's lateral geniculate body to moving stimuli.

The responses to moving stimuli of single cells in the parvo- and magnocellular layers (PCL and MCL) of the macaque lateral geniculate nucleus (LGN) have been studied. PCL cells respond with a monophasic increase or decrease in firing when a bar passes across the receptive field, according to the wavelength composition of the stimulus. MCL cells respond with a biphasic sequence of excitation and suppression or vice versa dependent on whether a cell is on-centre or off-centre and on stimulus contrast direction. With large stimuli, PCL cells respond as long as the stimulus covers the receptive field while MCL cells respond only at the contrast borders. MCL cell responses are maximal with bars just long enough to cover the field centre, while PCL cell responses show a variable relation with bar length, depending on stimulus wavelength and receptive field structure. PCL cells show broad velocity tuning while at least some MCL cells were more sharply tuned. Many cells in the macaque LGN show weak orientation or direction preference.

Animals↗
PubMed1978

Shapes and sounds as self-objects in learning geography.

The pleasure which some children find in maps and map reading is manifold in origin. Children cathect patterns of configuration and color and derive joy from the visual mastery of these. This gratification is enhanced by the child's knowledge that the map represents something bigger than and external to itself. Likewise, some children take pleasure in the pronunciation of names themselves. The phonetic transcription of multisyllabic names is often a plearurable challenge. The vocalized name has its origin in the self, becomes barely external to self, and is self-monitored. Thus, in children both the configurations and the vocalizations associated with map reading have the properties of "self=objects" (Kohut, 1971). From the author's observation the delight which some children take in sounding out geographic names on a map may, in some instances, indicate pre-existing gratifying sound associations. Childish amusement in punning on cognomens may be an even greater stimulant for learning than visual configurations or artificial cognitive devices.

Auditory Perception↗
PubMed1985

Bisecting rods and lines: effects of horizontal and vertical posture on left-side underestimation by normal subjects.

In Experiment I normal subjects performed the classical clinical line-bisection task, and demonstrated a left-side underestimation. In Experiment II subjects maintained fixation upon a central position and adjusted a rod passing through this fixation point so that both extremities were judged equal. The left-side underestimation was very much greater under these conditions, but was considerably reduced when retinal and gravitational coordinates were dissociated by making the subjects lie horizontally on one or other side. Subjects then demonstrated greater left-side and top-half underestimation when lying on the left than on the right side. Gravitational coordinates and the apparent locus of events in extrapersonal space are determinants of perceptual asymmetries at least as important as anatomical connectivities.

Adult↗
PubMed1990

On and off pathway contributions to apparent motion perception.

We studied the separability and/or interaction of the On and Off pathways in their role as inputs to visual motion perception. Using the long-range motion perception system, we asked if the motion system can use brightness polarity information, by testing whether correspondence is preferred between elements for which brightness polarity is preserved. We found such a preference, suggesting that brightness polarity information is indeed available to the motion system. However, under certain conditions motion is perceived even though the brightness polarity of apparent motion stimulus elements is reversed, indicating that the apparent motion system does integrate information from these two pathways. The source of the preference for maintaining polarity seems not to be the different brightnesses of the dark and bright stimulus elements, but the very fact that information must be integrated from different pathways. We relate the characteristics of the dependence of the motion perception on element contrast and contrast sign to those of previously reported visual evoked potential responses to brightness increments and decrements.

Contrast Sensitivity↗
PubMed1994

Visual search in continuous, naturalistic stimuli.

In standard visual search experiments, subjects look for a target item among distractor items. Targets and distractors are generally presented as isolated entities on a blank background. Do theories based on results of such experiments have any application to the real world of spatially continuous stimuli where "items" are not so conveniently delineated? Experiment 1 examines search for conjunctions of color with form and with orientation in novel stimuli designed to resemble aerial views. As with artificially isolated items, conjunction search with these complex stimuli is highly efficient, holding out the promise that models of visual search based on laboratory data can be extended to real-world situations. Experiment 2 shows that some "serial" searches are made significantly less efficient when items are embedded in these specific naturalistic backgrounds. This suggests that even classic serial searches rely on some parallel processing--the processing required to locate the "items" to be serially searched.

Attention↗