Biological differentiation

Existing models of physiologic and behavioral function and the nervous control of these events may bear reexamination on the basis of evidence for a process of differentiation in transduction processes. Biological differentiation provides a basic and intrinsic mechanism through which single neural, receptor, and effector mechanisms can modify the nature of their responses.     

Optimal temporal differentiation

In order to illuminate a light signaling a correct response, adult humans had to space their button presses according to a range of time requirements. In some conditions, the spacing needed only to exceed a minimum duration; in others, it had to fall between lower and upper bounds. Mean interresponse times always exceeded the lower limit, and decreased the more stringent were the upper bounds. Variability of interresponse times increased with larger lower bounds, but was unaffected by the size of the upper bound. Feedback about the direction of errors in conditions involving both upper and lower bounds did not affect the means, but it did reduce variability. Predictions were derived from optimality theory, based on the assumption that the critical factor was minimization of the time between correct responses. Without upper bounds, the theory overestimated the mean interresponse times by about 10%; with upper bounds, the theoretical predictions corresponded closely to the actual data. The results did not appear to reflect a scalar timing process. Optimality theory, in contrast to Weber's law, correctly predicted the variety of curves relating sensitivity to duration requirements.     

An anomalous brightness differentiation

The two adjacent regions of a homogeneous surface divided by a thin line may appear different in brightness. The phenomenon is weak, but can be obtained and systematically studied under certain experimental conditions. Data suggest that the effect is influenced by both the spatial position and the relative size of the two regions. The phenomenon is worthy of further examination because it challenges current theories of brightness perception.     

The differentiation of rhythmic structure

Listeners judged whether two five-tone nonmetric rhythms were the same or different. Each rhythm was presented one, two, or four times to study the process of perceptual differentiation. The results indicated that the listeners perceived these rhythms in-terms.of the grouping of the tones, and not in terms of the timing between the groups. Two rhythms that had the same perceptual grouping were judged as being identical, even if the timing between the groups was different. The perception of the groupings of tones developed gradually. If each rhythm was presented only once, then the listeners had only a global percept, focused on groups (runs) of three elements, and often judged two different rhythms as being identical. If the rhythms were presented two or four times, then the grouping of the tones became more differentiated and the listeners were less likely to judge different patterns as being identical. Thus, perception of auditory rhythmic structure appears to follow the same developmental process as the perception of visual spatial structure.     

A family of differentiation indices

A general class of differentiation indices is introduced for profiles of scores. Their ordinal properties and an application to Holland's classification system are examined. Comparison with other suggested indices is performed both theoretically and empirically.We are grateful to Professors J. Rayman and J. L. Holland for an interesting discussion. We would also like to thank Vera lachan for suggesting the problem.     

Social differentiation and social originality

In this article we have presented a theoretical outline and a body of empirical work relating to the processes of social differentiation and social originality. If, in a competition, someone else seems to possess a decisive advantage or if mere comparison with this other person constitutes a threat to social identity, there are signs, in given conditions, of a tendency to differentiate oneself from the other, to be different or to do something else, to invent new criteria of being or doing with others or to combine accepted criteria in an original way. In other words, one tends to give proof of originality or, to use a Darwinian metaphor, to occupy ‘vacant places’. Doubtless the strategies described here only apply to certain social systems in which the visibility of the agent is an important social value and in which comparison may pose a threat to that identity. The restoring of identity by way of the search for otherness merits the attention of social psychology. But originality is not necessarily accepted or not necessarily immediately. Innovation may take time, may necessitate the creation of schismatic groups and the waging of battles for recognition, etc. We give a brief account of observations made with regard to groups of children in summer camps, laboratory experiments and the results of surveys in the scientific and artistic communities which fit into our theoretical framework. It will not be difficult for the reader to see that this article is a first step in a direction which, in our eyes, holds out a great deal of promise.     

Pure timing in temporal differentiation

Temporal control appears to depend on whether the critical durations are those of stimuli or those of responses. Stimulus timing (temporal discrimination) supports Weber's law, whereas response timing (temporal differentiation) indicates decreasing relative sensitivity with longer time intervals. The two types of procedure also yield different conclusions in scaling experiments designed to study the functional midpoint of two or more durations (temporal bisection procedures). In addition, the fractional-exponent power relation between emitted and required duration usually found with animals in differentiation experiments conflicts with deductions from formal analyses. The experiment reported here derived from considering differentiation arrangements as schedules of reinforcement. When analyzed from this perspective, the procedures are tandem schedules involving a required pause followed by a response, and it is the pause alone that involves temporal control. A choice procedure separated timing from responding, and enabled observations of pause timing in isolation. Pure temporal control in differentiation consisted of linear overestimation of the standard duration, and Weber's law described sensitivity. These results indicate that the two problems, the fractional-exponent power relations and the apparently different nature of sensitivity in differentiation and discrimination, disappear when temporal control is observed alone in differentiation.     

Sex-role differentiation in contemporary communes

This research tests the hypothesis that the social interactions and sex roles of persons living in communes will become similar to those of persons in extended families, although the commune residents were raised in nuclear families. Commune residents and university students were asked to compare their present and their past social interactions in terms of 13 questions derived from established differences between nuclear and extended families. Commune residents, compared to students, described their present situation as less competitive, hostile, independent, and more cooperative. They also regard the statuses of men and women as more dissimilar than do students. Commune men are more likely to do more cross-sex-type chores than are male students, but still view their present and future status as higher than that of women. The findings confirm the hypothesis that communal social roles evolve to become similar to those in extended families, with the exception of work roles.This research was sponsored by the National Science Foundation Grant No. P2 S50810-000 and National Institute of Mental Health Grant No. R01 MH19589. Madison Holloway and Kathryn Gunning assisted in the data collection.