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PubMed2005

Auditory-visual intermodal matching of small numerosities in 6-month-old infants.

Recent studies have reported that preverbal infants are able to discriminate between numerosities of sets presented within a particular modality. There is still debate, however, over whether they are able to perform intermodal numerosity matching, i.e. to relate numerosities of sets presented with different sensory modalities. The present study investigated auditory-visual intermodal matching of small numerosities in infancy by using a violation-of-expectation paradigm. After being familiarized with events of a few objects impacting a surface successively, 6-month-old infants were alternatively presented with two and three tones while the movement of each object remained hidden behind an opaque screen. The screen was then removed to reveal either two or three objects. Results showed that the infants looked significantly longer at the numerically nonequivalent events (the three-tone/two-object and the two-tone/three-object events) than at the numerically equivalent events (the two-tone/two-object and the three-tone/three-object events) irrespective of the rate or duration of auditory tones presented. These findings suggest that infants are capable of performing intermodal matching of small numerosities and that they might possess abstract representations of numerosity beyond sensory modalities.

Auditory Perception↗
PubMed1990

Procedure-specific estimates of structural and strategic factors in the Horizontal-Vertical illusion.

The present study examined potential differences in structural and strategic factor estimates involved in the Horizontal-Vertical (HV) illusion. Performance on adjustment and production-task forms of the illusion was examined under the conditions of intertrial feedback, continued visual inspection, combined feedback and visual inspection, as well as control procedures. Estimates of structural and strategic factors were procedure-specific and, for each task, the correction of inaccurate strategic factors was significantly greater for the feedback than the visual-inspection and control groups. There were no significant additive effects when feedback was combined with visual inspection. The illusion results from an overestimation of the length of vertical lines, seems to be predominantly cognitive in nature, and exists in the absence of line bisection and a comparison line.

Adolescent↗
PubMed1996

The situational effects on haptic perception of rod length.

Three experiments were conducted to investigate situational effects (manipulation, range, and prior experience) on the haptic perception of rod length. Each rod was held between its two ends with one hand. In Experiment 1, 32 participants judged length of rods using different manipulations. Perceived lengths were found to be dependent on manner of manipulation and not necessarily equal to actual lengths. Different parameters were detected in different manipulations. In Experiment 2, 8 participants judged rod lengths by wielding rods of two ranges: long and short. Perceived length was found to be affected by the range of rods evaluated successively in a single set. In Experiment 3, 9 participants judged rod lengths after an experience of handling dense or light rods. Perceived length was found to be affected by prior experience. Results are discussed in terms of how rod lengths can be perceived accurately by haptic modality without involving direct perception.

Adult↗
PubMed1991

Effect of surface characteristics and style of production on naming and verification of pictorial stimuli.

Theories of object recognition that are based purely on part decomposition do not take into account the role of textural, shading, and color information, nor do they differentiate between stylistic factors in the preparation of line-drawn pictorial stimuli. To investigate these factors, naming and verification experiments were performed using line drawings, monochrome photographs, and color photographs of common objects. For line drawings, it was shown that line width, exposure, and contrast affected naming latency, which increased for lines of narrow width and extremes of exposure. Naming latencies were compared for objects drawn by a professional artist, with varying degrees of surface detail, and objects produced by a computer-aided design (CAD) system, with no surface detail. The mean naming latencies for the artist set were faster than for the CAD set, though not significantly, with a significant degree of object correlation being observed. However, in certain cases there were significant differences between objects. These were investigated in a further experiment in which subsets with common properties of present or absent surface detail were selected from the artist-drawn stimuli. It was found that the presence of surface features resulted in lower response latencies even for those objects that intuitively could be recognized by parts alone. The time to name photographic and line-drawn stimuli was compared, and a progressive decrease in naming latency from line to monochrome to color stimuli was observed. In a verification task, no significant advantage for color or monochrome photographs over line drawings was found, either when comparing stimuli of equivalent or of different mode. However, there was a tendency for the comparison of different modes to take longer than the comparison of same modes. The results are discussed in terms of theories of human visual processing and cognitive and computational models of object recognition.

Adult↗
PubMed1979

Body perception in athletes and non-athletes.

20 male athletes and 20 control subjects were required to make estimates of the length of their body dimensions and of external comparison objects. Athletes were more accurate in judging body dimensions than comparison objects while the reverse pattern was demonstrated by non-athletes. The results are discussed on the basis of the possible influence of sports activities on body perception.

Adolescent↗
PubMed2006

The planning of tool-to-object relations in young children.

This study investigated the way young children used a cane for displacing an object. In the experiment, 11 children with an average age of 32.3 months were asked to pick up a cane (hooked stick) that was located and orientated differently on each trial. With this cane they had to displace a target-object towards a free-to-choose goal location. The way the children used the cane for transporting the object was not determined by its starting location and orientation relative to the object. In fact, the children preferred enclosing the object in the hook, irrespective of the starting configuration. This contradicts a prediction that follows from an earlier study by Van Leeuwen et al. (1994). Final location of the target object and hand use was influenced by preferences as well as constraining task variables.

Child, Preschool↗
PubMed1979

Responses of single units in the monkey superior colliculus to moving stimuli.

1. Single unit responses of pan-directional cells to moving and stationary flashing stimuli were studied in the superficial layers of the superior colliculus in paralysed, anaesthetized rhesus monkeys. The aim of this study was to see how far cell responses to moving stimuli fit in with what would be expected from their responses to stationary flashing stimuli. 2. Both the leading and the trailing edge of a moving stimulus evoke a transient response. If the diameter of moving light spots is increased the strength of the leading edge response increases, reaches a maximum and decreases to a constant value which is similar to the behaviour of the on response when the diameter of flashing spots is increased. The strength of the trailing edge response increases and reaches the same strength as that of the leading edge response. If the width of a long moving slit is increased, the strength of the leading edge response is the same at all slit widths, while the strength of the trailing edge response shows a course similar to that of the trailing edge response if the spot diameter is increased. If the length of a wide moving slit is increased both the leading and the trailing edge responses decrease. These results indicate that the strength of both leading and trailing edge responses is dependent on the degree the inhibitory surround is activated. 3. The leading and the trailing edge of a stimulus evoke their responses at the same position in the receptive field independent of the direction of movement. 4. Increasing the velocity of a moving stimulus shows that in general the leading edge response is present up to higher velocities than the trailing edge response independent of the sign of contrast. The burst duration to moving stimuli decreases with increasing stimulus velocity and appears to be determined by the time a moving edge is present in the receptive field centre. When this time becomes shorter than 10--20 ms, the burst duration for moving stimuli is constant and about the same as for flashing stimuli. This indicates that, although spatial receptive field properties can vary considerably, temporal receptive field properties show a strong similarity among different units. 5. The response latencies to light and dark moving edges are the same, which in turn are about equal to the response latencies to stationary flashing stimuli. 6. Stimulation experiments show that the general response characteristics to moving stimuli can be predicted by using a set of receptive field parameters derived from responses to stationary flashing stimuli. The most important variable of moving stimuli appears to be the period of time a moving contour is present within the receptive field centre, besides the degree of activation of the inhibitory surround.

Animals↗
PubMed1990

The effects of varying fins in Müller-Lyer and Holding illusions.

Five experiments were conducted to determine how distortion of spatial position induced by unidirectional Müller-Lyer fins varied as a function of angle and length of fins. Research employing Cornsweet's staircase method yielded ambiguous results, but psychophysical methods of magnitude estimation, paired comparisons, and production showed conclusively that distortions of position are affected by angle and length of fins in a manner similar to that found in distortions of length. It was concluded that similar strategies are employed in processing attributes of length and position and that a theory based on averaging of attributes within an attentional field describes the performance of real observers.

Adult↗
PubMed2006

Kinematic cues and recognition of self-generated actions.

In the present study, we addressed the issue of whether healthy individuals can recognize a given gesture as their own, based on kinematic information. To this purpose, we required 36 volunteers to execute a series of hand movements of increasing complexity, while their kinematics was recorded by a motion-capture system. In a later session, we showed them a series of computer animations where a virtual hand, rendered as a simple stick-diagram, was animated by the kinematics recorded from the participants in the previous session. Their task was to recognize their own movements, choosing from three alternatives. To test the contribution of various potential cues to action recognition, the roles of (1) access to motor representation, (2) gesture complexity, and (3) familiarity effects were separately investigated. The results support the hypothesis that kinematic templates rather than single motor parameters contribute to self-recognition in the absence of morphological cues.

Adult↗
PubMed2001

Spatial range of illusory effects in Müller-Lyer figures.

The spatial range of the illusory effects in Müller-Lyer (M-L) figures was examined in three experiments. Experiments 1 and 2 assessed the pattern of bisection errors along the shaft of the standard or double-angle (experiment 1) and the single-angle (experiment 2) M-L figures: Subjects bisected the shaft and the resulting two half-segments of the shaft to produce apparently equal quarters, and then each of the quarters to produce eight equal-appearing segments. The bisection judgments of each segment were referenced to the segment's physical midpoints. The expansion or wings-out and the contraction or wings-in figures yielded similar patterns of bisection errors. For the standard M-L figures, there were significant errors in bisecting each half, and each end-quarter, but not the two central quarters of the shaft. For the single-angle M-L figures, there were significant errors in bisecting the length of the shaft, the half-segment, and the quarter, of the shaft adjacent to the vertex but not the second quarter from the vertex nor in dividing the half of the shaft at the open end of the figure into four equal intervals. Experiment 3 assessed the apparent length of the half-segment of the shaft at the open end of the single-angle figures. Length judgments were unaffected by the vertex at the opposite end of the shaft. Taken together, the results indicate that the length distortions in both the standard and single-angle M-L figures are not uniformly distributed along the shaft but rather are confined mainly to the quarters adjacent to the vertices. The present findings imply that theories of the M-L illusion which assume uniform expansion or contraction of the shafts are incomplete.

Adult↗
PubMed1989

Hemispheric differences in global versus local processing of hierarchical visual stimuli by normal subjects: new data and a meta-analysis of previous studies.

Twenty-four normal right-handed male subjects classified hierarchical visual stimuli (small letters arranged to form larger letters), which were presented separately to each cerebral hemisphere. Previous studies using similar paradigms have yielded mixed evidence for the specialization of local, analytic processing in the left hemisphere and global, holistic processing in the right hemisphere. No statistically significant evidence for such a pattern of specialization was evident in the results of the present study. However, when meta-analytic techniques were used to combine the present results with those from previous studies, there was evidence that the hypothesized left-hemisphere/local, right-hemisphere/global specialization does in fact exist.

Adult↗
PubMed2004

Visuomotor performance in a patient with visual agnosia due to an early lesion.

We tested a patient with visual agnosia who had suffered severe bilateral brain damage early in life, on a series of visuomotor tasks. The broad pattern of results confirms that S.B., like the extensively tested patient D.F., shows an impressive array of preserved skills, despite his severe perceptual problems. Also like D.F., S.B. shows certain subtle visuomotor difficulties that can be related to the idea that his partially intact occipito-parietal areas are unable to benefit from interactions with the apparently severely damaged occipito-temporal regions. Unlike D.F., however, he is able to make accurate discriminations of simple visual features, such as object width and orientation, albeit with very slow response times. We hypothesize that several factors such as the early onset of S.B.'s lesion and the long period since his brain lesion have allowed his brain to compensate to a degree what has been impossible in D.F., whose brain damage occurred in adulthood. This may include an element of 'rewiring' and self-monitoring of visuomotor processes that allow S.B. to achieve perceptual access to visual information processed in the dorsal stream: information that is normally only available for on-line visuomotor control.

Adult↗
PubMed1985

Separability and integrality of global and local levels of hierarchical patterns.

We used a constrained classification task to examine the perceptual relations between global and local levels in hierarchical patterns composed of many, relatively small elements and those composed of few, relatively large elements. In Experiments 1 and 3 subjects were asked to make classifications based on "form" or "texture." In Experiments 2 and 4 they were asked to classify according to the "shape" of the configuration or the elements. The results indicate that configural and elemental levels are perceptually separable for many-element patterns when processed as form and texture: Subjects could attend to either level without being affected by variation along the irrelevant dimension. However, when the same many-element patterns were processed for global and local shape, subjects could not selectively attend to either level. For few-element patterns, global configuration and local elements appeared to be perceptually integral dimensions. These results are relevant to two issues: the global precedence hypothesis and the explanations of integral and separable dimensions.

Adolescent↗