Temporal aspects of slant and inclination perception.

Linear transformations (shear or scale transformations) of either horizontal or vertical disparity give rise to the percept of slant or inclination. It has been proposed that the percept of slant induced by vertical size disparity, known as Ogle's induced-size effect, and the analogous induced-shear effect, compensate for scale and shear distortions arising from aniseikonia, eccentric viewing, and cyclodisparity. We hypothesised that these linear transformations of vertical disparity are processed more slowly than equivalent transformations of horizontal disparity (horizontal shear and size disparity). We studied the temporal properties of the stereoscopic slant and inclination percepts that arose when subjects viewed stereograms with various combinations of horizontal and vertical size or shear disparities. We found no evidence to support our hypothesis. There were no clear differences in the build-up of percepts of slant or inclination induced by step changes in horizontal size or shear disparity and those induced by step changes in vertical size or shear disparity. Perceived slant and inclination decreased in a similar manner with increasing temporal frequency for modulations of transformations of both horizontal and vertical disparity. Considerable individual differences were found and several subjects experienced slant reversal, particularly with oscillating stimuli. An interesting finding was that perceived slant induced by modulations of dilation disparity was in the direction of the vertical component. This suggests the vertical size disparity mechanism has a higher temporal bandwidth than the horizontal size disparity mechanism. However, conflicting perspective information may play a dominant role in determining the temporal properties of perceived slant and inclination.     

No prevalence of right-left over top-bottom spatial codes

Reaction time is known to depend on spatial stimulus-response compatibility in both the horizontal and the vertical dimensions. However, if both dimensions are varied in the same task, horizontal but not vertical compatibility affects performance, even if subjects are instructed to attend to the vertical dimension only (Nicoletti & Umiltà, 1984). Experiment 1 compared the effect of horizontal and vertical instructions in a task with left- versus right-handed key responses placed at a top versus bottom location. A horizontal-prevalence effect was observed only with a horizontal, and not with a vertical, instruction. This suggests that subjects might not have heeded the vertical instruction in the Nicoletti and Umiltà study but instead attended to the horizontal dimension. Experiment 2 did not yield any horizontal prevalence with one-handed responses (joystick movements). This indicates that top-bottom codes become ineffective only if the responses suggest an exclusively horizontal response coding. In sum, results demonstrated multiple spatial coding of stimuli and responses under appropriate conditions and suggest that the right-left codes do not dominate the top-bottom spatial codes.     

Vertical versus horizontal spatial compatibility: Right-left prevalence with bimanual responses

For two-choice tasks in which stimulus and response locations vary along horizontal and vertical dimensions, the spatial compatibility effect is often stronger on the horizontal than vertical dimension. Umiltà and Nicoletti [(1990) Spatial stimulus-response compatibility (pp. 89–116). Amsterdam: North-Holland] attributed this right-left prevalence effect to an inability to code vertical location when horizontal codes are present simultaneously. Hommel [(1996) Perception & Psychophysics, 43, 102–110] suggested instead that it reflects a voluntary strategy. This study reports four experiments that examine this issue. Experiment 1 was a conceptual replication of Hommel's Experiment 1, with responses made on a numeric keypad and subjects instructed in terms of the vertical or horizontal dimension. The results replicated Hommel's findings that showed a right-left advantage with horizontal instructions; however, with vertical instructions, we found a benefit of vertical compatibility alone that he did not. This benefit for vertical compatibility alone was eliminated in Experiment 2 using a varied practice schedule similar to that used by Hommel. Experiment 3 showed right-left prevalence and a benefit of vertical compatibility alone, even with varied practice and vertical instructions, when subjects responded on perpendicularly arranged handgrips. These benefits were eliminated in Experiment 4 using Hommel's method of urging subjects to respond only in terms of the instructed dimension. With bimanual responses, right-left prevalence is a robust phenomenon that is evident when comparing across vertical and horizontal instructions and, when the right-left distinction is relatively salient, within the vertical instructions condition alone. Received: 4 February 2000 / Accepted: 5 May 2000     

The mean-integral representation of rectangles

To assess perceptual interaction between the height and width of rectangles, we used an accuracy variant of the Garner paradigm. We measured the discriminability of height and width (baseline tasks) and size and shape (correlated tasks). From thed′ values in these conditions, we estimated perceptual distances and inferred amean-integral representation in which height and width corresponded to nonindependent dimensions in a perceptual space. This model accounted well for performance in these two-stimulus conditions, and it also explained 70% –80% of the decline in performance in selective and divided attention. In a second experiment, conducted for purposes of comparison with the rectangle discrimination Experiment, we studied the discrimination of horizontal and vertical line segments connected in an L-shape. In size discrimination, observers were equally good with line pairs and rectangles, suggesting holistic perception; but in shape discrimination, they appeared to combine information from the two line-pair components of the rectangle independently. The mean-integral model was again successful in relating performance in the Garner tasks quantitatively.     

How configurations of binocular disparity determine whether stereoscopic slant or stereoscopic occlusion is seen

A partially occluded contour and a slanted contour may generate identical binocular horizontal disparities. We investigated conditions promoting an occlusion resolution indicated by an illusory contour in depth along the aligned ends of horizontally disparate line sets. For a set of identical oblique lines with a constant width added to one eye's view, strength, depth, and stability of the illusory contour were poor, whereas for oblique lines of alternating orientations the illusory contours were strong, indicating a reliance on vertical size disparities rather than vertical positional disparities in generating perceived occlusion. For horizontal lines, occlusion was seen when the lines were of different lengths and absolute width disparity was invariant across the set. In all line configurations, when the additional length was on the wrong eye to be attributed to differential occlusion, lines appeared slanted consistent with their individual horizontal disparities. This rules out monocular illusory contours as the determining factor.     

Assessing underreporting response bias on the MMPI-2

The authors assess the replicability of the two-factor model of underreporting response style. They then examine the relative performance of scales measuring these styles in analog (ARD) and differential prevalence group (DPG) designs. Principal components analysis produced a two-factor structure corresponding to self-deceptive (SD) and impression management (IM) response styles. The IM factor scale and related individual validity scales were elevated among research participants instructed to fake good on the MMPI-2 as compared with participants who completed the MMPI-2 under standard instructions (ARD) and among individuals evaluated in real-life assessment contexts where underreporting is expected (DPG). Participants in DPG samples produced significantly higher SD factor and related individual scale scores than did the ARD participants instructed to fake good. These findings confirm that the MMPI-2 validity scales measure two types of underreporting styles and that these styles may operate differently in ARD versus DPG designs.     

Are Judgments of Linear Size More Accurate When Based on an Affordance?

Perceptual judgments of size affect a wide variety of activities but can be difficult to measure. Two methods of estimating size (linear extent) were compared. One required adjustment of the distance between a point created by a laser beam and a fixed reference line; the other involved adjusting the separation of 2 vertical posts. Two groups of adults were instructed to use these methods to indicate either simple linear extent ("width") or the affordance of passability (minimal opening) for identical dimensions of objects and their own bodies. Afterward, the participants completed a survey including the Eating Attitudes Test (EAT-26). Accuracy did not vary with instructions or EAT-26 scores. As predicted, accuracy was found to be lower for participants whose body weight had recently changed by 5% or more, presumably due to a less refined attunement to their current body sizes. Higher accuracy was expected for both the method (posts) and instructions ("opening") that should foster affordance-based judgments. Despite the greater ease and precision of the laser-based method, more accurate estimates were made using movable posts. These results are discussed in terms of 2 contrasting perceptual modes.     

Effects of visual information and task constraints on intersegmental coordination in playground swinging

The authors investigated how and to what extent visual information and associated task constraints are negotiated in the coordinative structure of playground swinging. Participants (N = 20) were invited to pump a swing from rest to a prescribed maximal amplitude under 4 conditions: normal vision, no vision, and 2 visual conditions involving explicit phasing constraints. In the latter conditions, participants were presented with a flow pattern consisting of a periodically expanding and contracting optical structure. They were instructed to phase the swing motion so that the forward turning point coincided with either the maximal size (enhanced optical flow) or the minimal size (reduced optical flow) of the presented flow pattern. Removal of visual information clearly influenced the swinging behavior, in that intersegmental coordination became more stereotyped, reflecting a general stiffening of the swinger. The conditions involving explicit phasing requirements also affected the coordination, but in an opposite way: The coordination became less stereotyped. The two phasing instructions had differential effects: The intersegmental coordination deviated more from normal swinging (i.e., without phasing constraints) when optical flow was enhanced than when it was reduced. Collectively, those findings show that visual information plays a formative role in the coordinative structure of swinging, in that variations of visual information and task constraints were accompanied by subtle yet noticeable changes in intersegmental coordination.     

Effects of Visual Information and Task Constraints on Intersegmental Coordination in Playground Swinging

The authors investigated how and to what extent visual information and associated task constraints are negotiated in the coordinative structure of playground swinging. Participants (N = 20) were invited to pump a swing from rest to a prescribed maximal amplitude under 4 conditions: normal vision, no vision, and 2 visual conditions involving explicit phasing constraints. In the latter conditions, participants were presented with a flow pattern consisting of a periodically expanding and contracting optical structure. They were instructed to phase the swing motion so that the forward turning point coincided with either the maximal size (enhanced optical flow) or the minimal size (reduced optical flow) of the presented flow pattern. Removal of visual information clearly influenced the swinging behavior, in that intersegmental coordination became more stereotyped, reflecting a general stiffening of the swinger. The conditions involving explicit phasing requirements also affected the coordination, but in an opposite way: The coordination became less stereotyped. The two phasing instructions had differential effects: The intersegmental coordination deviated more from normal swinging (i.e., without phasing constraints) when optical flow was enhanced than when it was reduced. Collectively, those findings show that visual information plays a formative role in the coordinative structure of swinging, in that variations of visual information and task constraints were accompanied by subtle yet noticeable changes in intersegmental coordination.     

The Müller-Lyer illusion in touch and vision: implications for multisensory processes

In six experiments, we used the Müller-Lyer illusion to investigate factors in the integration of touch, movement, and spatial cues in haptic shape perception, and in the similarity with the visual illusion. Latencies provided evidence against the hypothesis that scanning times explain the haptic illusion. Distinctive fin effects supported the hypothesis that cue distinctiveness contributes to the illusion, but showed also that it depends on modality-specific conditions, and is not the main factor. Allocentric cues from scanning an external frame (EF) did not reduce the haptic illusion. Scanning elicited downward movements and more negative errors for horizontal convergent figures and more positive errors for vertical divergent figures, suggesting a modality-specific movement effect. But the Müller-Lyer illusion was highly significant for both vertical and horizontal figures. By contrast, instructions to use body-centered reference and to ignore the fins reduced the haptic illusion for vertical figures in touch from 12.60% to 1.7%. In vision, without explicit egocentric reference, instructions to ignore fins did not reduce the illusion to near floor level, though external cues were present. But the visual illusion was reduced to the same level as in touch with instructions that included the use of body-centered cues. The new evidence shows that the same instructions reduced the Müller-Lyer illusion almost to zero in both vision and touch. It suggests that the similarity of the illusions is not fortuitous. The results on touch supported the hypothesis that body-centered spatial reference is involved in integrating inputs from touch and movement for accurate haptic shape perception. The finding that explicit egocentric reference had the same effect on vision suggests that it may be a common factor in the integration of disparate inputs from multisensory sources.     

Orientation-contingent tactual size aftereffects

A new contingent aftereffect of apparent size can be produced in the following way. A rectangular inspection block is oriented with its long dimension horizontal (or vertical). During an inspection (induction) period of 2 min, the subject alternately grasps the horizontal and vertical dimensions of the inspection block between the thumb and forefinger of a single hand, changing from one dimension to the other every 2 sec. After the inspection period, the hori zontal dimension of a square test block feels shorter (or longer) than the vertical dimension. Inspection blocks having larger ratios of width to height produce larger aftereffects. The aftereffect persists over delays of as much as 16 min between inspection and test.     

Human figure drawing size and body image in preschool children from a self-physique perspective

To learn about the relationship between size of human figure drawings and the physiques of children, we investigated body image characteristics in childhood by using the Human Figure Drawing test. Height, weight, Kaup Index (a body mass index for children) and Human Figure Drawing traits (vertical height, horizontal width, waist size, surface area of head, surface area of the self-drawing) were measured for drawings of 122 4- to 6-yr.-old children (62 boys, 60 girls). Analysis showed that boys, who are physically larger than girls, produced self-drawings with somewhat larger surface areas. For vertical height of self-drawings of boys, 4-yr.-olds characteristically made taller self-drawings than 5-yr.-olds. While we hypothesized that taller children would make vertically taller self-drawings, we observed a negative relationship between children's physical height and the vertical height of the self-drawings. 4-yr.-old boys showed the most interest in their own physical height, making taller drawings and in doing so gave a clue to an early childhood feature of body image.     

Estimation of height for persons in pictures

We report three experiments in which subjects estimated the height of persons seen in pictures. In Experiment 1, 50 realistic photographs were used as targets. The correlation between mean estimated height and actual height was .92, and target’s sex and the ratios of head to trunk, which included horizontal ratio (i.e., a ratio of head width to shoulder width) and vertical ratio (i.e., a ratio of head height to stature), were found to be effective on height estimates, although target’s sex was more effective than ratios of head to trunk. In Experiments 2 and 3, the recognizability of target persons was reduced, respectively, by inverting the person photographs and by degrading the various features of the photographs. The main results were that (1) the correlation between mean estimated height and actual height was .88 for the inverted photographs and was .80, on average, for the degraded drawings; (2) target’s sex was consistently influential in both experiments; (3) vertical ratio was effective for the inverted photographs and the mildly degraded drawings but not for the extremely degraded drawings in which only outlines of target persons were depicted; and (4) the estimation for the outlined pictures was likely to be influenced by fit of clothes to targets’ bodies. From these findings, person stimuli were considered to provide a stable metric stick of visual space under naturalistic circumstances.     

Deformation of the useful visual field with state of vigilance,task priority,and central task complexity

In a dual-task situation, peripheral perception can deteriorate due to different variables related to the experimental situation, such as central task complexity and the relative priority given to the two tasks. Recent studies have also shown that individual characteristics (such as the state of vigilance) can alter the useful visual field. The ability to perceive signals presented at different places in the visual field decreases in situations that lead to episodes of low vigilance. In Exp. 1, 27 subjects (18-29 years) had to perform a monotonous and prolonged dual-monitoring task involving central and peripheral vision. The test was carried out with two different sets of instructions regarding priority: the more important task was either the central task or the peripheral one. In Exp. 2, 18 subjects (18-30 years) performed the same test, but this time with two levels of complexity of the central task, either a simple monitoring activity or the same monitoring task coupled with a counting activity. Elliptical interpolation of the data enabled assessment of the deformation of the useful visual field in both experiments. The analysis of the parameters of the elliptical model indicated that the useful visual field mainly shrinks on the vertical axis, as the individual becomes drowsy. The useful visual field also shrinks on the horizontal axis when the peripheral task has priority and the monitoring activity is prolonged, or when the central task is complex.     

Detecting and Discriminating Between Random Responding and Overreporting on the MMPI-A

The utility of traditional validity scales in detecting random responding and overreporting on the MMPI-A and in discriminating between these two response sets was investigated in a sample of 89 clinical and nonclinical adolescents aged 14 to 17 years. The overreporting group consisted of 24 nonclinical adolescents instructed to complete the MMPI-A as if they were trying to create an impression of psychological disturbance. The random group included 20 nonclinical adolescents instructed to complete the MMPI-A answer sheet without access to the test booklet. Clinical (n = 20) and nonclinical (n = 25) standard groups completed the MMPI-A under the standard instructions. Results showed that validity scales designed to detect random responding and overreporting on the MMPI-A were quite effective in doing so. Significant differences between groups and high classification rates were noted. In addition, the VRIN scale was found to be sensitive only to random responding, whereas Scale F was sensitive to both random responding and overreporting. Scale L also was found to be sensitive to random responding, and support for the utility of the F - K index in identifying overreported adolescent profiles was obtained.     

Attention,instruction, and response representation

A two-dimensional Simon-type task was devised to investigate the impact of task requirements and explicit instructions on spatial action coding. Subjects performed actions that were defined on two spatial dimensions: horizontal (left-right) or vertical (top-bottom). The relevant stimulus feature was nonspatial but the stimuli varied on the horizontal and the vertical dimension, so that horizontal and vertical S-R compatibility effects could be measured separately. Implicit task requirements were manipulated by having the subjects perform an unrelated task before the Simon task—a task in which only one of the two spatial dimensions was relevant. Instructions were varied by describing the responses in the unrelated priming task and/or in the Simon task in spatial terms or by referring to nonspatial features of the response keys. Priming a particular dimension increased the Simon effect on that dimension, whereas instructions had no differential effect. These findings suggest that, first, drawing attention to a particular dimension leads to a stronger contribution to event representation of those features defined on that dimension (intentional weighting) and, second, that instructions do not affect action coding if the manipulation does not change the task goal.     

The effects of practice with one positive set in a memory scanning task can be completely transferred to a different positive set

Recognition tasks in which the items have been assigned to one and only to one response category throughout an experiment typically reveal that the functions relating reaction time and positive set size are negatively accelerated and have slopes which decrease significantly with practice. The present experiments were designed to determine whether this practice effect is specific to the individual items practiced or if it depends, at least partially, on relations built up among the positive set items. The results permit rejection of both alternatives. In the extreme case tested, it was found that, after prolonged practice with the same items composing nested positive sets, these items could be replaced with unpracticed ones without producingany significant change in the effect of set size, reaction times, or error levels. Absence of change in overall reaction times in combination with stability of slope values leads to the conclusion that not only do those practice effects which are related to the set-size effect transfer exceedingly well to unpracticed items, but practice effects on all other stages involved in item recognition also show almost total transfer to unpracticed items. It is concluded that, under the conditions of these experiments, the gain (through practice) in efficiency in processing the stimulus is independent of the stimulus.     

TEACHING CONSERVATION OF WEIGHT BY MEANS OF VERBAL INSTRUCTIONS

Three groups of preschool children were given verbal instructions as to the invariance of weight in spite of transformations of shape. Instructions were phrased according to the principles of reversibility, decentering, and addition-subtraction, respectively. A fourth group received no verbal information but only external reinforcement. Verbally instructed groups were superior to control and nonverbal groups on a posttest. On transfer and counter-suggestion items the addition-subtraction group had a tendency towards superior performance.     

Response set effects in recognition memory

In three experiments, Ss responded to individual digits or letters according to whether or not each was in some prememorized list. There were either two possible responses (yes-no condition) or a single response (yes-only and no-only conditions). With memory sets of one, two, or four digits, RT was a linear function of memory set size. The slope of the function was least under the yes-only condition and greatest under the yes-no condition. Nonspecific practice had little effect on any of the slopes. With memory sets of 4, 8, or 12 letters, the slopes under the yes-only and yes-no conditions did not seem to differ, and practice with specific sets flattened the function considerably in both cases. Overall, the errors under the yes-no condition were mostly false alarms, those under the no-only condition mostly misses, and those under the yes-no condition were divided about equally. The results are interpreted partially in terms of a multiple-observations model of decision time.     

Tolerance of geometric distortions in infant's face recognition

The aim of the current study is to reveal the effect of global linear transformations (shearing, horizontal stretching, and vertical stretching) on the recognition of familiar faces (e.g., a mother's face) in 6- to 7-month-old infants. In this experiment, we applied the global linear transformations to both the infants’ own mother's face and to a stranger's face, and we tested infants’ preference between these faces. We found that only 7-month-old infants maintained preference for their own mother's face during the presentation of vertical stretching, while the preference for the mother's face disappeared during the presentation of shearing or horizontal stretching. These findings suggest that 7-month-old infants might not recognize faces based on calculating the absolute distance between facial features, and that the vertical dimension of facial features might be more related to infants’ face recognition rather than the horizontal dimension.