Children's strategic compensation for size underconstancy: Dependence on distance and relation to reasoning ability

When asked to judge the size of a distant object, older children are more likely than younger ones to report deliberately inflating their judgements to compensate for size underconstancy (Granrud, in press). The current investigation examined whether use of this strategy depends on object distance and whether it is related to individual differences in reasoning, knowledge about size perception, or cognitive style. In two studies, children in Grades 1–3 estimated the size of a distant (61 m away) and near (6.1 m away) disc. In each, half of the children reported inflating their judgement of the distant disc to compensate for a tendency to underestimate its size, but only a few reported using this strategy for the near disc. Self-reported strategy users tended to either judge the distant disc accurately or to overestimate its size, whereas the other children tended to underestimate its size. Strategy reporters obtained higher scores on a test of verbal reasoning, but did not differ from the other children in reflectivity-impulsivity. In Study 1, strategy reporters also showed a better understanding of how distance affects the apparent size of objects in photographs. This understanding was strongly related to verbal reasoning ability. In Study 2, visuospatial reasoning ability was also found to predict who would report strategy use, and this predictive relation was independent of verbal reasoning ability.     

Roles of Visual Information for Control of Reaching Movements in Children

Poststroke hemiparetic individuals (n = 9) and a control group (n = 9) completed a frequency-scaled circle-drawing task in unimanual and bimanual conditions. Measures of intralimb spatial and temporal task accuracy and interlimb coordination parameters were analyzed. Significant reductions in task performance were seen in both limbs of the patients and controls with the introduction of bimanual movement. Spatial performance parameters suggested that the 2 groups focused on different hands during bimanual conditions. In the controls, interlimb coordination variables indicated predictable hand dominance effects, whereas in the patient group, dominance was influenced by the side of impairment and prior handedness of the individual. Therefore, in this particular bimanual task, performance improvements in the hemiplegic side could not be elicited. Intrinsic coupling asymmetries between the hands can be altered by unilateral motor deficits.     

Evidence Supporting the Importance of Peripheral Visual Information for the Directional Control of Aiming Movement

The focus of the present study was on determining whether the high level of directional accuracy found in aiming studies in which the subjects can see their hand in the visual periphery supports the existence of a kinetic visual channel or, rather, the advantage of binocular over monocular vision for movement directional control. The limits of this kinetic visual channel were also explored. The results of the 1st experiment indicated that seeing one's hand in the visual periphery is sufficient to ensure optimal directional aiming accuracy. Further, no differences in aiming accuracy were noted between monocular and binocular vision. These results supported the existence of a visual kinetic channel. In the 2nd experiment, whether this kinetic visual channel would operate with movements slower (55°/s) than those usually used in studies that had proved its existence (over 110°/s) was determined. The results indicated that this visual kinetic channel was operative even at relatively slow movement velocities. Central vision of the hand seemed to be used for on-line directional control of relatively slow movements.     

Paleolithic Art and Cognition

In this article, I have explored some of the possible relationships between the first appearance of representational art in human history and the early development of human cognition. I argue that most Upper Paleolithic depictions directly represent generalized mental images of their animal subjects rather than percepts or recollected scenes from life and that these images, in turn, are representations of concepts at the basic level of categorization. A common feature of Paleolithic art forms is the salience of parts, and the treatment of parts indicates analytic and synthetic (recombinative) abilities. There are some indications of superordinate categorization. An expansion of conceptual thinking seems to be implied as well as the beginnings of operational thought. The presence and practice of depiction may have had the effect of bringing concepts into consciousness and thus inducing reflection in at least a partially abstract mode.     

Visual Consciousness and The Phenomenology of Perception

Ideally, psychological and phenomenological studies of visual experience should be mutually informative. In that spirit, this article outlines parts of Maurice Merleau‐Ponty's phenomenological view of visual experience as a kind of independently active opaque bodily synthesis, and uses those views to (a) help ground and extend Alva Noë's rejection of the “snapshot” theory of visual experience in favor of a more enactive view of visual content, (b) critique a failing of Noë's account, and (c) show how the assumptions underlying more internalist and Cartesian views of visual experience can illegitimately creep in even when they are being carefully criticized.     

The Visuomotor System Resists the Horizontal-Vertical Illusion

The effect of the horizontal-vertical illusion on the visual and visuomotor systems was investigated. Participants (N = 8) viewed horizontal and vertical lines in an inverted-T stimulus and judged whether the two line segments were the same or different lengths. Participants also reached out and grasped either the vertical or the horizontal line segment of the stimulus. Perceptually, participants succumbed to the illusion; that is, they judged Ts of equal horizontal and vertical line lengths to be different and Ts of unequal line lengths to be the same. When reaching toward the same stimuli, however, the size of their grip aperture was scaled appropriately for the various line lengths. Thus, whereas the perceptual system succumbed to the illusion, the visuomotor system did not. Those results support a model proposed by M. A. Goodale and A. D. Milner (1992), who posited separate cortical pathways for visual perception and visually guided action.     

Stimulus Generalization and the Peak Shift with Movement Stimuli

Stimulus generalization is suggested as an alternative method for examination of the “novelty? problem in motor learning. These experiments demonstrated that stimulus generalization occurs using simple movements as stimuli. The phenomenon of the “peak shift? in post-discrimination generalization gradients was also examined. The first experiment demonstrated that a peak shift occurred using linear movements as stimuli and that the magnitude of the peak shift increased as the difference between the training stimuli decreased. The second experiment showed similar results when the stimuli consisted of a range of movements rather than a single movement length. The final experiment provided evidence that perception of movement length is influenced by the magnitude of an immediately preceding movement. The relevance of these studies to current motor-learning theory is discussed.     

The Dynamics of Visual Reweighting in Healthy and Fall-Prone Older Adults

Multisensory reweighting (MSR) is an adaptive process that prioritizes the visual, vestibular, and somatosensory inputs to provide the most reliable information for postural stability when environmental conditions change. This process is thought to degrade with increasing age and to be particularly deficient in fall-prone versus healthy older adults. In the present study, the authors investigate the dynamics of sensory reweighting, which is not well-understood at any age. Postural sway of young, healthy, and fall-prone older adults was measured in response to large changes in the visual motion stimulus amplitude within a trial. Absolute levels of gain, and the rate of adaptive gain change were examined when visual stimulus amplitude changed from high to low and from low to high. Compared with young adults, gains in both older adult groups were higher when the stimulus amplitude was high. Gains in the fall-prone elderly were higher than both other groups when the stimulus amplitude was low. Both older groups demonstrated slowed sensory reweighting over prolonged time periods when the stimulus amplitude was high. The combination of higher vision gains and slower down weighting in older adults suggest deficits that may contribute to postural instability.     

Decay in Visuomotor Representations During Manual Aiming

The time course of the decay of spatial representations used for planning and controlling manual aiming has not been established. The authors' purpose in the present investigation was to generate a psychometric function for memory-guided reaching movements. Eight university-aged students performed a reciprocal tapping task for 10 s. Participants could see the targets for 5 s; then, vision of the targets was occluded. The present findings provide mixed support for 2 prominent theories concerning memory representations. Variability increased concurrently with the removal of vision of the targets, supporting the real-time hypothesis. However, a brief plateau in the curve was apparent for approximately 2 s after vision was removed, consistent with the use of a highly accurate representation for action.     

Endings as gain: The capacity to end and its role in creating space for growth

The paper describes an application of child psychotherapy in a paediatric setting. It examines the crucial part that attention to endings played in a clinical intervention where the phantasy of going on for ever threatened to inhibit growth. Case material is used to illustrate the different meanings and functions of endings and their significance in terms of parenting issues and developmental tasks. In this context the concept of negative elasticity is put forward as a useful tool for exploring the nature of boundaries. The final part of the paper focuses on the value of the external-reality experience of ending, its relationship to potential professional omnipotence and the importance of sustaining a tension between inner- and outer-world factors.