Measuring reaction time and controlling the video display in experiments on an IBM PC

The problems of using the IBM PC XT/AT or their clones in experiments are recognized because of the slow, inadequate and awkward timing procedures of these microcomputers. Some specific solutions to these problems are described, including a compiled BASIC approach using real time procedures accurate to 1 millisecond (although resolution to 1 microsecond can be achieved) and synchronization of the video display with the program. Programs are available from the authors on receipt of a 5 1/4 inch floppy disc or $10.     

Pattern preferences at birth and their interaction with habituation-induced novelty preferences

Three experiments are described which relate to models of infant visual preferences, and to the ways in which preferences can be modified or created by habituation. In all experiments newborn babies were used as subjects. In Experiments equated 1 and 2 infants were presented with pairs of stimuli that were equated for contour density but which differed in spatial frequency components. The preferences obtained give support to Banks and Salapatek's (1981, Journal of Experimental Child Psychology, 31, 1-45) model of infant preferences which predicts that the maximally preferred stimulus will be that which contains high amplitude spatial frequency components falling within the age group's peak contrast sensitivity. In Experiment 3 an infant-controlled habituation procedure was used. The results obtained suggest that strong natural preferences based on the infants' peak contrast sensitivity cannot be changed by habituating infants either to the preferred or to the nonpreferred member of a stimulus pair. However, where no prior preference exists between two stimuli that are perceptually highly discriminable, very strong novelty preferences are found after habituating newborns to either stimulus. The results suggest that the contrast sensitivity model can be a powerful predictor of preferential looking in newborns, and in addition are further evidence that preferences based on experience can be found from birth.     

Age differences and similarities in the effects of cues and prompts

A series of 6 experiments investigated the use of cues and prompts by younger and older adults. Cues provide useful information about an impending target, even though the information is not always valid. Prompts provide an instruction about what aspect of the target is to be responded to. The costs and benefits of cues were most consistent with models in which the attentional resources that are shifted in response to the cue were as large or larger in older adults as they were in younger adults. The results with both cues and prompts converged on the conclusion that the time course of processing and using a cue or prompt is the same in younger and older adults. The attentional resources tapped by these procedures cannot be the diminished processing resource to which many age differences in cognitive performance are attributed.     

The corneal reflection technique and the visual preference method: sources of error.

Corneal reflection techniques for eye fixation position measurement have been used in recent years to assess such variables of visual behavior as duration of looking and the area(s) of the stimulus fixated. These techniques are especially useful when measuring visual regard in infants and young children as head restraints are not required. In an earlier article the present authors demonstrated, empirically, that the common assumption that the center of the pupil represents the line of sight is untenable. The present article considers the causes of the errors present in these techniques: it can be shown that theoretical calculations of these sources of error, calculations based both on the anatomy of the eye, and on the optics involved, produce good agreement with their empirically derived magnitudes.     

Intermodal perception at birth: Intersensory redundancy guides newborn infants’ learning of arbitrary auditory−visual pairings

In this study the ability of newborn infants to learn arbitrary auditory–visual associations in the absence versus presence of amodal (redundant) and contingent information was investigated. In the auditory-noncontingent condition 2-day-old infants were familiarized to two alternating visual stimuli (differing in colour and orientation), each accompanied by its ‘own’ sound: when the visual stimulus was presented the sound was continuously presented, independently of whether the infant looked at the visual stimulus. In the auditory-contingent condition the auditory stimulus was presented only when the infant looked at the visual stimulus: thus, presentation of the sound was contingent upon infant looking. On the post-familiarization test trials attention recovered strongly to a novel auditory–visual combination in the auditory-contingent condition, but remained low, and indistinguishable from attention to the familiar combination, in the auditory-noncontingent condition. These findings are a clear demonstration that newborn infants’ learning of arbitrary auditory–visual associations is constrained and guided by the presence of redundant (amodal) contingent information. The findings give strong support to Bahrick’s theory of early intermodal perception.     

Semantic networks: visualizations of knowledge

The history of semantic networks is almost as long as that of their parent discipline, artificial intelligence. They have formed the basis of many fascinating, yet controversial, discussions in conferences and in the literature, ranging from metaphysics through to complexity theory in computer science. Many excellent surveys of the field have been written, and yet it is our belief that none of them has examined the important link between their use as a formal scheme for knowledge representation and their more heuristic use as an informal tool for thinking. In our consideration of semantic networks as computerized tools, we will discuss three levels of abstraction that we believe can help us understand how semantic networks are used. I.