Rectangles may appear to reverse like trapezia when they rotate at an uneven rate.

A 1983-1985 theory by Mitchell and Power predicts that, when rotating rectangles undergo certain kinds of speed fluctuation, they should appear to reverse just as trapezia do. The prediction is partially confirmed. One of two 'mimic' rectangles underwent apparent reversals more often than a control rectangle undergoing even rotation and in the same places as rotating trapezia. However, its reversal frequency was less than those of the trapezia, and a second 'mimic' slowed an inappropriate distribution of reversals round the cycle. These anomalies call for some modification to Mitchell and Power's theory, but minor qualifications may be sufficient.     

Dummett's intuitionism is not strict finitism

Michael Dummett's anti-realism is founded on the semantics of natural language which, he argues, can only be satisfactorily given in mathematics by intuitionism. It has been objected that an analog of Dummett's argument will collapse intuitionism into strict finitism. My purpose in this paper is to refute this objection, which I argue Dummett does not successfully do. I link the coherence of strict finitism to a view of confirmation — that our actual practical abilities cannot confirm we know what would happen if we could compute impracticably vast problems. But to state his case, the strict finitists have to suppose that we grasp the truth conditions of sentences we can't actually decide. This comprehension must be practically demonstrable, or the analogy with Dummett's argument fails. So, our actual abilities must be capable of confirming that we know what would be the case if actually undecidable sentences were true, contradicting the view of confirmation. I end by considering objections.I especially want to thank Alex George and Philip Kitcher for their help on this paper. I'd also like to thank the members of the Propositional Attitudes Task Force, Jane Braaten, Jay Garfield, Lee Bowie, Murray Kitely and Tom Tymoczko. My thanks also to Peter Godfrey-Smith and the anonymous reviewers of Synthese, one of whom was particularly helpful.     

The effects of strong belief structures on information-processing evaluations and choice

This study examined the influence of the strength of belief structures on selected aspects of the decision-making process. To examine these issues, a business-acquisition decision scenario was studied in an experiment. Subjects played the role of a CEO of an electronics firm and were asked to evaluate the attractiveness of six potential acquisition candidates and to rate various aspects of the associated decision process. We presented half the subjects with information that the belief structure of their organization was extreme, agreed upon, and clear. The other half was presented with information that there was disagreement about the belief structure and that it was more ambiguous and less extreme. The results clearly showed that the decision process is different for people who were presented with an agreed-upon, extreme, and tightly constructed belief structure when compared to those who received information reflecting a weak and loosely constructed belief structure. A strong belief structure resulted in less positive evaluations, information requested, and money allocated to explore incompatible acquisition candidates (and vice versa for a highly compatible candidate) when compared to subjects using a weak belief structure. In addition, subjects in the strong-belief condition reported that their decision process would be characterized by less doubt, less time, less difficulty, and less conflict compared to subjects in the weak-belief structure condition. Implications for both decision theory and practical decision processes are discussed.     

Conditional probability judgments: Effects of imagining vs experiencing the conditioning event

Applications of Bayesian conditionalization often involve two temporal aspects: a probability judgment is based on knowledge at a point in time and is revised over time in light of added information. Let t, t′, and t″ designate three chronological points in time. E designates a target event which occurs or not at t″, and C designates a conditioning event which occurs or not at t′. Suppose that an individual judges P(EC) at t. If C occurs, Bayesian conditionalization requires that a judgment of P(E) at t′ is equal to the earlier judgment of P(EC). However, inconsistencies may result because a judgment of P(EC) at t is based on imagining C, while a judgment of P(E) at t′ is based on experiencing C. This study examines two sources of such inconsistencies. First, C normally is an abstraction of what might happen between t and t′. What actually happens may differ, such that an individual observes extraconditional information which affects a judgment of P(E) at t′. Second, experiencing C may change an individual's affective state, leading to greater optimism or pessimism about the occurrence of E. We report an experiment which documents both effects.     

Personality,time of day and delayed memory for tv news

An experiment was conducted to test the effects of time of day on delayed memory for televised news stories. Three groups received the same sequence of 6 news stories at 09.30, 13.30 and 16.30, respectively. Unexpected tests of free recall, cued recall and recognition were given about 2 hr after news presentation. Results showed that memory performance improved slightly across the day on tests of recall, and significantly so on recognition. Personality differences were also examined. In general, introverts remembered more than extraverts and differences between them were most marked during the late-afternoon session especially on free recall and when minimal cuing was provided. The results support previous time-of-day findings for delayed retention of complex learning materials. Personality differences observed here are consistent with predicted introvert-extravert differences in memory performance predicted by Eysenck's modified action-decrement hypothesis.     

Operant conditioning permits voluntary,noninvasive measurement of blood pressure in conscious,unrestrained baboons (Papio cynocephalus)

This report describes a computerized apparatus and procedure for completely automated noninvasive measurement of systolic, diastolic, and mean arterial blood pressure in conscious, unrestrained nonhuman primates. We used a specially constructed, cage-mounted oscillometric blood pressure instrument and operant reward conditioning methods to train adult baboons(Papio cynocephalus) to submit voluntarily to frequent self-initiated determinations of their blood pressures in the absence of a human operator/observer. Details concerning the operant training procedure and illustrative blood pressure data are presented. The accuracy of the method was evaluated by comparing the noninvasive blood pressure readings with simultaneously taken direct measurements obtained by means of chronically indwelling arterial catheters.     

Extinction of morphine analgesic tolerance

It has been suggested that the analgesic effect of morphine becomes attenuated over the course of successive administrations by a conditional, compensatory, hyperalgesic response elicited by the administration procedure, thus accounting (in part) for analgesic tolerance. On the basis of this associative model of tolerance, it would be predicted that established tolerance would be extinguished by placebo sessions. In experiments of apparently similar design (but conducted by different experimenters in different laboratories), data both confirming and refuting this prediction have previously been published. The present experiment, conducted jointly by the experimenters who reported the divergent findings, was designed to determine the reasons for the different results. It was found that placebo sessions do consistently attenuate morphine analgesic tolerance. Such extinction is not limited to the experimenter, drug preparation, rat strain, or apparatus used in the original, successful demonstration of the phenomenon, but rather is also demonstrable under conditions similar to those used in subsequent experiments which failed to demonstrate extinction of tolerance. Results of the present experiment suggest that the failures to demonstrate extinction of tolerance were attributable to insufficient extinction training.     

Environmental adaptation of the mental patient

An ecological model suggests looking at the hospitalized mental patient in terms of how well the resources available in the environment fit his individual needs. This study explores the relationship between the environmental fit of patients while they are in the hospital and their adaptation to the community once they have left. Data on individual needs and evaluations of environmental resources were obtained through a series of structured interviews. Results indicate that the more a patient feels the hospital environment is a good fit, the longer he stays there. Hospital fit is positively related to fit in the community, but the latter is related only to the degree of symptomatology exhibited by the expatient in the community and not to how long he is able to remain out of the hospital. Implications of the findings and the model are discussed.     

Body movement and inattention in learning-disable and normal children

Four experiments were conducted to test various aspects of an optimal level of arousal model of hyperactivity in learning-disabled children. Vigilance performance and level of body movement were measured while learning-disabled and control children performed in an auditory vigilance task. The results suggested that body movement increased throughout the vigilance task, increased rates of external stimulation result in decreased level of body movement, and learningdisabled children differed from controls in showing higher levels of body movement and poorer vigilance performance. The results were discussed in terms of changes in arousal level and compensatory stimulus-seeking behavior.