Perception and its neuronal mechanisms

A classic view of the relation between sensorineural activity and perception has assumed that the former is somehow transformed into the latter at some locus in the brain. This notion conflicts with the modern view that the activity of the nervous system is restricted to transmitting and processing information. It is suggested that the conflict may be resolved by considering perception as reflective activity rather than passive reception. This cognitive process entails information about the perceiving self and the general context and not merely the stimulus input. Some aspects of perception can be related to neuronal mechanisms and even to neuronal activity at specific loci. How is this done? By identifying the characteristics of the perceptual process and finding a necessary and sufficient neuronal mechanism that receives information about the stimulus input and can perform the implied computation. Examples are taken from the study of visual development in human infants.     

Believability and syllogistic reasoning

In this paper we investigate the locus of believability effects in syllogistic reasoning. We identify three points in the reasoning process at which such effects could occur: the initial interpretation of premises, the examination of alternative representations of them (in all of which any valid conclusion must be true), and the "filtering" of putative conclusions. The effect of beliefs at the first of these loci is well established. In this paper we report three experiments that examine whether beliefs have an effect at the other two loci. In experiments 1 and 2 subjects drew their own conclusions from syllogisms that suggested believable or unbelievable ones. In the third experiment they evaluated conclusions that were presented to them. The data show that beliefs both affect the examination of alternative models and act as a filter on putative conclusions. We conclude by showing how some types of problem and some problem contents make the existence of alternative models more obvious than others.     

The development of separability in visual perception

Under conditions that do not allow focused attention, reports of illusory conjunctions (i.e. errors that wrongly recombine the features of different objects) constitute evidence of the separate registering of features at an early processing level. The occurrence of illusory conjunctions was used to determine whether there is preattentive analysis of component dimensions (colour and form) and of parts of shapes (triangles and arrows) in young children aged 5 to 8 years. Evidence of preattentive analysis was found, even for the youngest children, for colour and form but not for parts of shapes. Although developmental effects hardly reached significance, inspection of abilities assumed to affect the illusory conjunctions phenomenon suggests that at the preattentive stage children can integrate spatially separate segments but lack the capacity to fully analyse connected segments.     

Dynamic organization of intersensory function

Issues related to infant intersensory functioning are reviewed. The argument is offered that limitations of sensory inputs during early stages of development are necessary and provide structure and organization which determine behavioural characteristics at later stages. It is also suggested that infant organisms respond to the intensity of stimulation rather than organizational characteristics and that this is responsible for the form of sensory equivalence apparent during early development. A scheme for the investigation of sources of intersensory organization is presented which involves a prospective analysis of how consideration of the times of onset of sensory functions helps us to understand intra- and intersensory development. The advantages of this experimental approach are outlined.     

The composition of imaginal transformations

Three experiments examine the performance of composite imaginal spatial transformations using tasks in which people perform pairs of distinct imaginal transformations either in close succession or simultaneously. The principal aim of the investigation is to determine, for both modes of composition, whether imaginal transformations combine interactively or noninteractively to determine the temporal course of imaging performance. Specifically, does the time to imagine a given composite transformation reflect the independent contributions of its component transformations, or do component transformations have different effects within different composites? Results obtained under a number of distinct task conditions are most consistent with the proposal of noninteractive composition. However, the temporal effects of particular imaginal transformations are neither consistent nor readily predictable across different task conditions. Implications of these results for analogue-spatial models, task demand, and procedural accounts of imaging are discussed.     

The infant's use of visual and haptic information in the perception and recognition of objects

The purpose of this paper is to discuss the relationship between the haptic and visual systems during infant's bimodal interaction with objects. Four general topics are discussed: the role of exploratory activity in perception, the specific ways in which the two systems are related during exploration, developments over age in the relationship between the systems, and the impact of the organism/environment relationship on these developments.     

A sermon from hell: Toward a theology of loneliness

Loneliness as part of the human condition is first explored from an experiential-philosophical perspective. A biblical survey suggests loneliness is normative to the faith experience and may portray a more realistic religiosity. Desert imagery in Scripture indicates a strong association among solitude, spiritual development, and potential dangers of spiritual deception. God's not yet-ness-itself a cause of existential loneliness—is paradoxically the way in which communion with God functions in the here and now. The creative use of solitude may enhance social, psychological, and spiritual well-being, and provide a way to theologize about personal isolation and disorientation.He is also editor of theHarding Journal of Religion and Psychiatry.     

An exploratory study of planning, attention, simultaneous, and successive cognitive processes

Although there has been a considerable amount of research on simultaneous and successive processing (Luria's second functional unit) by Das and others, there have been relatively few investigations into the measurement of attention and planning (the first and third functional units, respectively). The purpose of this investigation was to examine the factorial validity of tasks designed to measure cognitive processing in each of Luria's three functional units. A sample of 112 normal fourth- and fifth-grade students were administered nine experimental tasks chosen or developed according to the theoretical components of planning, attention, simultaneous, and successive processes. Principal factor analyses (orthogonal and oblique) with rotation of four factors resulted in solutions that closely matched the anticipated groupings based on a structural analysis of the tasks. General support for the feasibility of measurement of Luria's cognitive processing model, and the need to further develop and refine these and other experimental tasks, was obtained.     

On the limits of the matching concept in monkeys (Cebus apella).

Two cebus monkeys, with many years of experience matching a variety of static visual stimuli (forms and colors) within a standard matching-to-sample paradigm, were trained to press a left lever when a pair of displayed static stimuli were the same and to press a right lever when they were different. After learning the same/different task, the monkeys were tested for transfer to dynamic visual stimuli (flashing versus steady green disks), with which they had no previous experience. Both failed to transfer to the dynamic stimuli. A third monkey, also with massive past experience matching static visual stimuli, was tested for transfer to the dynamic stimuli within our standard matching paradigm, and it, too, failed. All 3 subjects were unable to reach a moderate acquisition criterion despite as many as 52 sessions of training with the dynamic stimuli. These results provide further evidence that, in monkeys, the matching (or identity) concept has a very limited reach; they consequently do not support the view held by some theorists that an abstract matching concept based on physical similarity is a general endowment of animals.     

Interhemispheric transfer in schizophrenics, depressives, and normals with schizoid tendencies

Although several studies suggest that schizophrenics suffer from an impairment in the interhemispheric transfer (IHT) of information, methodological weaknesses in these studies preclude clear interpretation of their results. This study addresses these criticisms in order to provide a clearer test of the IHT theory. Schizophrenics, depressives, normal controls, and normals with schizoid tendencies were assessed on five measures of IHT (verbal and nonverbal dichotic listening, intermanual transfer, bimanual block design, finger sequence repetition) and two measures of unilateral hemispheric processing (lateral eye movements, auditory thresholds). Results consistently failed to support an IHT deficit interpretation of schizophrenia. Schizoid normals had a significantly greater right-ear advantage on verbal dichotic listening than both psychiatric groups, a result suggesting enhanced left-hemisphere activation in schizoid normals. It is concluded that the IHT theory requires stronger empirical substantiation than has been obtained to date to warrant further consideration as a central theory of schizophrenia.