The role of three-dimensional depth cues in infants' perception of partly occluded objects

Newborn infants were familiarized to a three dimensional display consisting of a rod which moved behind a central occluder, so that only the top and bottom of the rod were visible. The infants' eyes were 38 cm from the rod and the occluder was 15 cm in front of the rod, a separation intended to ensure that the gap between the two was detected by the infants. On subsequent test trials the infants looked longer at a complete rod than at two rod pieces, suggesting that the hidden unity, or completeness of the rod had not been perceived. In a study by Johnson and Náñez (in press), using computer. generated stimuli, 4 month olds perceived the hidden unity of a similar display presented on a VDU in the complete absence of three. dimensional depth cues. Taken together, these findings suggest that, for these displays, perception of three. dimensional depth cues is not necessary for the detection of the unity of partially hidden objects. It is suggested that age changes in early infancy in the perception of occluded objects may result either from the emergence of abilities to perceive objects from kinematic information or from the emergence of sensitivity to that information itself.     

Neurocardiac toxicity of racemicd,l-lactate fluids

Racemicd,l-lactate has long been used in burn therapy as Ringer’s lactate and in peritoneal dialysis fluid for treatment of renal failure. The d-lactate component of this racemic mixture is known to cause two forms of neurological toxicity in patients: encephalopathy and, in a subset of the population, panic reaction. Here we demonstrate that coma, similar in degree to that produced by blood levels of 75 mM ethanol was induced in rats by the intraperitoneal infusion of sodiumd-lactate sufficient to raise serumd-lactate concentration to 25 mM, whereas infusion of equal quantities of sodiuml-lactate produced no observable neurological effect. We further demonstrate that the intravenous infusion of racemicd,l-lactic acid into 48-hour fasted rats produced serious disturbances of cardiac rate and rhythm leading to death. When serumd-lactate concentration had reached 1–2 mM there was bradycardia, at 2–3 mM prolongation of QT interval, at 6–7 mM AV block with ectopic escape rhythms, and at 11 mM death in ventricular standstill or fibrillation. In contrast, intravenous infusion ofl-lactic acid to blood levels of 25 mM failed to produce any change in cardiac rhythm. On the other hand, the isolated working heart, free of influence from the central nervous system, displayed no change of cardiac rhythm or physiological function when perfused with 25 mM sodiumd,l-lactate.     

Form perception at birth: Cohen and Younger (1984) revisited

Cohen (1988; Cohen & Younger, 1984) has suggested that there is a shift in the perception of form sometime after 6 weeks of age. Prior to this age infants can remember the specific orientations of line segments, but cannot process and remember the angular relations that line segments can make. Experiment 1 used simple line stimuli with newborn infants to test this suggestion. Following habituation to a simple two-line angle the newborns dishabituated to a change of orientation but not to a change in angle, confirming Cohen and Younger's suggestion that orientation is a powerful cue in early shape perception. In Experiments 2 and 3 newborns were familiarized either to an acute or to an obtuse angle that changed its orientation over trials. On subsequent test trials the babies gave strong novelty preferences to a different angle. Alternative interpretations of the results are discussed, but these experimental findings are compatible with the suggestion that newborns can quickly learn to process angular relations, and that rudimentary form perception may not be dependent on a lengthy period of learning and/or maturation for its development.     

Early cognitive development and parental education

Relations between cognitive development in infancy and early childhood, and parental education were examined. Previous research has found little association between measures of the parenting environment, including parental education and socio‐economic status (SES), and cognitive development in infants and children under 2 years of age. However, the earlier studies may not have reliably measured individual differences in cognitive abilities, thus, there is uncertainty as to what age elements in the parental environment affect cognitive development. Seventy‐six infants were tested on a range of cognitive tasks at 3‐month intervals between the ages of 9 and 18 months. Information on parental education (a component of SES) was collected. Seventy‐one of the children returned at 27 months and completed the Bayley Scales of Infant Development, Mental Scale, which was used as an outcome measure for the earlier tasks. The findings present a clear indication that cognitive development in early childhood is affected by the parenting environment, at least from as early as 12 months. Copyright © 1999 John Wiley & Sons, Ltd.     

Conditions for young infants' failure to perceive trajectory continuity

When viewing an event in which an object moves behind an occluder on part of its trajectory, 4-month-old infants perceive the trajectory as continuous only when time or distance out of sight is short. Little is known, however, about the conditions under which young infants perceive trajectories to be discontinuous. In the present studies we focus first on infants' perception of trajectories that change during a period of occlusion. Four-month-olds perceive discontinuity in trajectories that change in height or orientation while behind an occluder, and this is true even when a change in direction could be due to an invisible bouncing collision with a surface. Further experiments reveal that infants do not perceive diagonal linear trajectories as continuous across an occlusion unless the occluding and revealing edges are orthogonal to the path of movement. Implications for theories of perceptual and cognitive development are discussed.     

Imagined contact as a prejudice‐reduction intervention in schools: the underlying role of similarity and attitudes

The present research tested a prejudice‐reduction intervention based on imagined contact. White children imagined interacting with a child from an ethnic out‐group (Asian) once a week for 3 weeks, or did not take part in this activity (control group). Compared with the control group, children who engaged in imagined contact subsequently showed more positive attitudes, greater perceived similarity, and willingness for intergroup contact. The effect of the intervention on willingness for contact was mediated by positive attitude change. Implications for imagined‐contact theory and the development of prejudice‐reduction techniques for schools are discussed.     

Gödel's and Other Paradoxes

Francesco Berto has recently written “The Gödel Paradox and Wittgenstein's Reasons,” about a paradox first formulated by Graham Priest in 1971. The major reason for disagreeing with Berto's conclusions concerns his elucidation of Wittgenstein's understanding of Gödel's theorems. Seemingly, Wittgenstein was some kind of proto‐paraconsistentist. Priest himself has also, though in a different way, tried to tar Wittgenstein with the same brush. But the resolution of other paradoxes is intimately linked with the resolution of the Gödel Paradox, and with understanding Wittgenstein's views of Gödel's theorems. So this paper discusses some other paradoxes before looking at Wittgenstein's relevant views.