Effects of direction and magnitude of horizontal disparities on binocular unmasking

Conditions under which binocular unmasking (BU), as an analogue of binaural unmasking, occurs have been explored. Observers were to detect through a stereoscope a Gabor signal in patches of two-dimensional broadband gaussian noise surrounded by a frame of uniform noise. The right-eye gaussian field was displaced relative to the left eye so that it appeared either in front of or behind the frame. Performance when signal disparity was equal to that of the noise--a condition functionally equivalent to monocular processing--was compared to that obtained when signal disparity was zero--a case in which BU should occur. Enhanced signal detectability of up to 12 dB and of nearly constant magnitude was observed in the latter condition when uncrossed disparities of up to 67.60 min visual angle and display durations of 1 s were employed. Signal detectability declined appreciably with increasing disparity (both crossed and uncrossed) when display duration was reduced to 90 ms, thus preventing the occurrence of compensatory vergence eye movements. It is suggested that BU effects may result from a process of linear summation of monocular inputs.     

Book reviews

Jacknedoff, R. (1985). Semantics and cognition. Cambridge, MA: The MIT Press, Pp. 283. ISBN 0-262-60013-7. £ 9.95.

Lakoff, g. (1987). Women, fire and dangerous things : What categories reveal about the mind. Chicago, IL.: Chicago University Press. Pp. 624. ISBN 0-266-46803-8. £19.95.

Longuet-Higgins, H. C. (1987). Mental processes : Studies in cognitive science. Cambridge, MA: The MIT Press. Pp. 424. ISBN 0-262-12119-0. £22.50.

Nowakowska, M. (1986). Cognitive sciences: Basic problems, new perspectives, and implications for artificial intelligence. Orlando, FL: Academic Press. Pp. 379. ISBN 0-12-522620-9. £44.50.

Winograd, T. & Flores, F. (1986). Understanding computers and cognition: A new foundation for design. Norwood, NJ: Ablex. Pp. 207. ISBN 0-89391-050-3. £23.

Weisberg, R. W. (1986). Creativity: Genius and other myths. New York:W. H.Freeman and company. Pp. 169. ISBN 0-1767-1769-7. £9.95.

Bosshardt, H. R. S. G (1986). Perspektiven auf Sprache. Berlin : Walter de Gruyter. Pp. 326. ISBN 3-11-010068-1. DM134.00.     

Is there anything out there? A study of distal attribution in response to vibrotactile stimulation

Patterns of vibrotactile stimulation were delivered to the index fingertips of naive blindfolded subjects. The attributions made by these subjects when they were allowed to experience transformations of vibrotactile stimulation correlated with self-movement were assessed. Although the subjects became aware of the relationship between self-movement and stimulation transformation, they never developed the hypothesis of distal attribution, ie the hypothesis that the ultimate cause of their vibrotactile experience was an encounter with an object in the environment. It is proposed that further investigations of the course of acquisition of distal attribution in the situation described may be instructive in the study of externalization in other modalities.     

Model Selection of Nested and Non-Nested Item Response Models Using Vuong Tests

Abstract

In this paper, we apply Vuong’s general approach of model selection to the comparison of nested and non-nested unidimensional and multidimensional item response theory (IRT) models. Vuong’s approach of model selection is useful because it allows for formal statistical tests of both nested and non-nested models. However, only the test of non-nested models has been applied in the context of IRT models to date. After summarizing the statistical theory underlying the tests, we investigate the performance of all three distinct Vuong tests in the context of IRT models using simulation studies and real data. In the non-nested case we observed that the tests can reliably distinguish between the graded response model and the generalized partial credit model. In the nested case, we observed that the tests typically perform as well as or sometimes better than the traditional likelihood ratio test. Based on these results, we argue that Vuong’s approach provides a useful set of tools for researchers and practitioners to effectively compare competing nested and non-nested IRT models.