Panum’s fusional area estimated with a criterion-free technique

It has been reported that criterion-free estimates of the upper disparity limits for fusion of line targets are small enough to be accounted for by monocular vernier sensitivity. However, targets such as lines, which contain high spatial frequencies, may ensure small fusion limits, since fusion limits obtained with criterion-dependent methods for narrow-band targets, such as sinusoids or difference-of-Gaussian luminance profiles, are proportional to target spatial periods. Experiment 1 therefore explored whether criterion-free methods give fusion limits for narrow-band targets that can be accounted for by vernier sensitivity. Vertical fusion limits were estimated by a method that forced observers to discriminate a disparate sinusoidal grating from an immediately adjacent zero-disparity grating. Fusion limits were too large to be explained by monocular vernier thresholds obtained for the same targets. In addition, fusion limits were not affected by large changes in target contrast, whereas vernier thresholds increased as contrast was decreased. The results of Experiment 1 also argued against interocular suppression as the cause of single vision, since vernier offsets that were visible when viewed monocularly were invisible under binocular viewing conditions. In Experiment 2, manual adjustment of disparities yielded fusion limits little different from those obtained with the forced-choice method of Experiment 1, demonstrating that it is possible to design adjustment methods for assessing fusion limits that are as sensitive as forced-choice methods. In Experiment 3, large reductions in target contrast, which have the effect of decreasing disparity sensitivity, did not alter fusion limits, disconfirming the idea that fusion limits estimated with discriminative procedures represent disparity-detection thresholds. In Experiment 4, disparities were adjusted until a just noticeable difference in grating contrast appeared. These disparities were larger than fusion limits, indicating that fusion limits did not represent a change in apparent contrast arising from disparity limitations of binocular summation. Together, the four experiments support the existence of binocular fusion as a unique category of sensory performance, disconfirm several nonfusional explanations of single vision, and support the use of criterion-free as well as adjustment methods in measuring fusion limits.     

American base‐rate neglect: It is not the math,but the context

We investigate cross‐cultural disparities in focalism bias through two studies of probability estimation. Using 60 American and 60 Chinese participants, Experiment 1 yields the standard finding that Americans manifest greater focalism bias by tending to neglect background probability base‐rates and to rely more heavily on obtained samples in estimating true probabilities, whereas Chinese participants show little tendency to ignore base‐rates. In Experiment 2, the phrasing of the probability‐estimation task is changed to bring base‐rates into the focus of the problem statement, again using a sample of 60 Americans and 60 Chinese. This allows us to test whether cross‐cultural differences result from a tendency to focus on the sample, and ignore ‘context’ (i.e., the background base‐rates), rather than simply a discrepancy in mathematical facility between the two groups. The results show far less base‐rate neglect for Americans, but essentially no change for Chinese (who always use base‐rate information, regardless of how presented). This outcome argues against the explanation that Americans are poorer Bayesians simply because they are weaker mathematicians. Implications are discussed.     

Book reviews

Balsam, P. D. and Tomie, A. (Eds.) Context and learning. Hillsdale, N.J.: Lawrence Erlbaum Associates. 1985. Pp. xi+ 419. ISBN 0-89859-442-1. £39.95.

Greenberg, G. and Tobach, E. (Eds.). Behavioral evolution and integrative levels: The T. C. Schneirla Conference Series. Hillsdale, N. J., Lawrence Erlbaum Associates. 1984. Pp. 307. ISBN 0-89859-363-8. $34.50. £28.75.

Commons, M. L. and Nevin, J. A. (Eds.). Quantitative analyses of behavior. Vol. 1: Discriminative properties of reinforcement schedules. Cambridge, Mass.: Ballinger. 1981. Pp. xxvii + 437. ISBN 0-88410-377-3 (v.1). Hardback. $42.50.

Lynch, G., McGaugh, J. L. and Weinberger, N. M. (Eds.). The neurobiology of learning and memory. New York: The Guilford Press. 1984. Pp. 528. ISBN 0-89862-645-5. £65.00.

Toates, F. M. Motivational systems. Cambridge: Cambridge University Press. 1986. ISBN 0-521-26854-0 (Hardback) £22.50; ISBN 0-521-31894-7 (Paperback) £7.95.     

The development of moral beliefs: A retrospective study

The present study tested a model of moral belief development based on Erikson’s (1963) and McAdams’ (1989) theories of personality development. The sequence of moral belief development is beliefs about outcomes, outcome certainty, beliefs about humanity, and social concern. The developmental antecedents of these beliefs were measured using 13 rationally constructed scales based on background data items. The belief and developmental scales were given to a sample of 246 undergraduates. Using a series of hierarchical blocked regressions, we found a pattern among the beliefs that supported a stage or contingent sequence model of belief development. The results suggest that a supportive, conventional and consistent family environment is a major antecedent of beliefs about outcomes and outcome certainty. Adjustment to the demands of adult culture rather than peer culture is the major antecedent of belief about humanity and social concern. Parts of this research were supported by a grant from the U.S. Office of Naval Research (Contract No. N00014-91-J-4167), Michael D. Mumford and Theodore L. Gessner, Principal Investigators.     

Smart Technology and the Moral Life

Smart technology is recording and nudging our intuitive and behavioral reactions in ways that are not fully shaped by our conscious ethical reasoning and so are altering our social and moral worlds. Beyond reasons to worry, there are also reasons to embrace this technology for nudging human behavior toward prosocial activity. This article inquires about four ways that smart technology is shaping the individual moral life: the persuasive effect of promptware, our newly evolving experiences of embodiment, our negotiations with privacy, and our experiences of risk and serendipity.