The influence of depth segmentation on colour constancy

In real scenes, surfaces in different depth planes often differ in the luminance and chromatic content of their illumination. Scene segmentation is therefore an important issue when considering the compensation of illumination changes in our visual perception (lightness and colour constancy). Chromatic adaptation is an important sensory component of colour constancy and has been shown to be linked to the two-dimensional spatial structure of a scene (Werner, 2003 Vision Research 43 1611 - 1623). Here, the question is posed whether this cooperation also extends to the organisation of a scene in depth. The influence of depth on colour constancy was tested by introducing stereo disparity, whereby the test patch and background were perceived in either the same or one of five different depth planes (1.9-57 min of arc). There were no additional cues to depth such as shadows or specular highlights. For consistent illumination changes, colour constancy was reduced when the test patch and background were separated in depth, indicating a reduction of contextual influences. An interaction was found between the influences of stereo depth and spatial frequency on colour constancy. In the case of an inconsistent illumination change, colour constancy was reduced if the test patch and background were in the same depth plane (2-D condition), but not if they were separated in depth (3-D condition). Furthermore, colour constancy was slightly better in the 3-D inconsistent condition than in the 2-D inconsistent condition. It is concluded that depth segmentation supports colour constancy in scenes with inconsistent illumination changes. Processes of depth segmentation are implemented at an early sensory stage of colour constancy, and they define visual regions within which the effects of illuminant changes are discounted for separately. The results support recent models that posit such implementation of scene segmentation in colour constancy.     

Immunizing the self: self-concept stabilization through reality-adaptive self-definitions

Processes of self-concept immunization are introduced as a way of reconciling self-concept protection against threatening information with the necessity of acknowledging own failure or losses. Self-immunization works by adaptively changing the subjective operationalization of personal traits, such that skills that individuals believe themselves to be good at are conceived as highly diagnostic, whereas skills that persons do not believe they possess are considered less diagnostic. Three studies are presented to investigate this stabilizing process. Correlational as well as experimental and longitudinal data support the assumption that self-immunization stabilizes central and abstract aspects of the self-concept without ignoring negative information on concrete skills.     

Book reviews

Women in the Footsteps of the Buddha. Struggle for Liberation in the Therigāthā . Katheryn R. Blackstone, 1998, London, Curzon Press xiv + 186 pp., ISBN 0 7007 0962 2

The Supreme Wisdom of the Upanisads. An Introduction. Klaus G. Witz, 1998, Delhi, Motilal Banarsidass xxv + 558 pp., hb Rs 700, ISBN 81 208 1573 4

The Original Analects: Sayings of Confucius and his Successors. E. Bruce Brooks & A. Takeo Brooks (Trans.), 1998 New York, Columbia University Press 368 pp., ISBN 0 2311 0430 8     

Book reviews

Confucian Traditions in East Asian Modernity: moral education and economic culture in Japan and the four mini‐dragons Tu Wei‐Ming (Ed.), 1996 Cambridge, MA, Harvard University Press ii + 418pp., hb £28.50, pb £12.50, ISBN 0 674 16086 X (hb)

The Recluse of Loyang: Shao Yung and the moral evolution of early Sung thought Don J. Wyatt, 1996 Honolulu, University of Hawaii Press xii + 340 pp., hb (price not given), ISBN 0 8248 1755 9

Rude Awakenings: Zen, the Kyoto School and questions of nationalism James W. Heisig & John C. Maraludo (Eds), 1995 Honolulu, University of Hawaii Press hb $40.00, pb $19.95

Untying the Knots in Buddhism. Selected essays Buddhist Tradition Series Volume 28, 1997 Alex Wayman 1997 Delhi, Motilal Banarsidass x + 618 pp, hb Rs. 495; ISBN 81 208 1321 9

Historical Dictionary of Hinduism Historical Dictionaries of Religions, Philosophies, and Movements, No. 13 Bruce M. Sullivan 1997 Lanham, MD & London, The Scarecrow Press xviii, 346 pp, pb £46.55, ISBN 0 8108 3327 1

Dictionary of Philosophy and Religion. Eastern and Western thought (New and enlarged edition; first 1980) William L. Reese, 1996 New York, Humanities Press xiv + 856 pp., pb, ISBN 0 391 03864 8     

Intrusiveness and Persuasive Impact of Three Communication Media1

Two field experiments compared the persuasive impact of communications delivered face-to-face, by telephone, or by letter. In both studies, letters did not differ from faccto-face contacts but telephone calls were less effective. In the second experiment, personalness interacted with communication medium such that addressing subjects by name reduced the impact of face-to-face encounters, increased that of letters, and had no effect on phone calls. A third sample of subjects rated the appropriateness of name usage by salespeople, indicating a salesperson should give his own name but was inappropriately personal when calling the subject by name. The findings support the notion that varying media and name usage varies the psychological distance between communicator and recipient. At appropriate psychological distances, communicators and communications have optimum effectiveness; at too great or too little distance, they lose impact. Thus, not only is selection of proper medium important to communicators but how the medium is used can affect impact.     

Complex learning and information processing by pigeons: a critical analysis

Three models of conditional discrimination learning by pigeons are described: stimulus configuration learning, the multiple-rule model, and concept learning. A review of the literature reveals that true concept learning is not characteristic of the behavior of pigeons in matching-to-sample, oddity-from-sample, or symbolic matching studies. Instead, pigeons learn a set of sample-specific S^D rules. Transfer of the discrimination to novel stimuli, at least along the hue dimension, is predicted by a “coding hypothesis”, which holds that pigeons make a unique, but usually unobserved response, R₁, to each sample, and that the comparison stimulus chosen depends on which R₁ was emitted in the presence of the sample. Convincing evidence is found that pigeons do code sample hues, but there is little evidence that allows one to infer that the “coding event” must have behavioral properties. Parameters of the conditional discrimination paradigm are identified, and it is shown that by appropriate parametric manipulation, a variety of analogous tasks may be generated for both human and animal subjects. The tasks make possible the comparative study of complex learning, attention, memory, and information processing, with the added advantage that behavior processes may be compared systematically across tasks.     

Opponent chromatic response functions for an average observer

Average opponent chromatic response functions are presented for use in quantitative models of color perception. Theoretical transformations of photopigment input are related to opponent channel activity. Opponent chromatic activity is, in turn, used to describe a theoretical huenaming curve for an average observer.