A propositional analyst’s assistant

A system (PAN) that is designed to assist both the inexperienced and the experienced user in performing propositional analysis is described. The system is implemented in UCSD Pascal on the Apple II and Apple He microcomputers.     

Does heart rate differentiate neurotic from normal people in a conditional reflex test?

This study is to compare heart reactivity between normals and anxiety neurotic patients. Five male and five female patients with anxiety neurosis and four male and five female normal persons were submitted to classic delayed conditional reflexes with different probabilities of reinforcement (shock), to a defensive instrumental conditional reflex, and to a neutral nonreinforced stimulus. The basal heart frequency was higher in neurotics and in women than in normals and men. The conditional stimulus (CS) associated with a shock generally produced a bradycardia in normal individuals and in neurotic men, but a tachycardia in neurotic women (effects most pronounced in cases with 100% shock probability). The instrumental CS caused a tachycardia in all of the groups, with highest values in neurotic women. The neutral stimulus produced bradycardia in all persons. The aftereffect of the light stimulus depended on whether a shock was administered and on the CS. The differences between neurotics and normals are explained as caused by the heightened excitatory level of the CNS of the neurotic group, produced by the unspecific activating effect of chronic anxiety, and differences of plastic processes in both groups, resulting in different effects of phasic anxiety on the heart. Complex inhibitory-excitatory interactions of the sympathetic and the vagal system underlying the heart rate changes may be assumed. Possible mechanisms leading to sex differences are discussed.     

Emerging from imaginary time

Recent models in quantum cosmology make use of the concept of imaginary time. These models all conjecture a join between regions of imaginary time and regions of real time. We examine the model of James Hartle and Stephen Hawking to argue that the various no-boundary attempts to interpret the transition from imaginary to real time in a logically consistent and physically significant way all fail. We believe this conclusion also applies to quantum tunneling models, such as that proposed by Alexander Vilenkin. We conclude, therefore, that the notion of emerging from imaginary time is incoherent. A consequence of this conclusion seems to be that the whole class of cosmological models appealing to imaginary time is thereby refuted.We would like to thank Quentin Smith for helpful comments on an carlier version of this eassy. Read Guy gratefully acknowledges support from the M.J. Murdock Charitable Trust.     

Artificial intelligence and animal psychology: A response to Boden, Margolis and Sloman

We propose the elements of an epistemological framework in which to situate the fundamental problem of ascribing mentalistic concepts to animals and machines that is posed by Margaret Boden's, Aaron Sloman's and Joseph Margolis' discussion of artificial intelligence and animal psychology.     

Study-time of sentences as a function of their specificity and of semantic exploration

In self-paced learning conditions the study-time of sentences is supposed to depend jointly upon the information content of the material and upon its exploration by the subject in the course of learning. In exp. 1 informative content was varied by using sentences constituted either of general or of specific words; study-time was found to be significantly longer for the latter sentences than for the former and the recall performance to be equal. Differential semantic exploration and storage were instigated by presenting in the series either pairs of similar, and thereby contrasted sentences, or isolated sentences. In exp. 2, study-time of the sentences was longer than that of the latter; but the first recall performance recorded with the constrasted sentences was also higher. The divergent effects of the nature of the material and of the activity of the subject upon study-time and recall performance were emphasized.     

Effects of a timing signal on simple reaction time with a rectangular distribution of foreperiods

It was hypothesized that the time course of preparation during a variable interstimulus interval (ISI) of a simple reaction time (RT) experiment was partly determined by the subjective distribution of conditional probabilities of the executive signal (ES). Sixty subjects performed a simple auditory RT task with various ranges of six ISI durations organized in rectangular frequency distributions. In order to give the subjects information about elapsed time during ISI, a recurring time-marking click, the periodicity of which was varied, was introduced during the ISI in one of the three series of trials each subject performed. A strong decreasing RT--ISI relationship was observed supporting the main hypothesis. However, a clear increase of mean RT over all ISIs combined, was also found. Because these two mixed effects were greatest when the click intervened at the possible times of ES occurrence only, three functions of time-information given by the click are discussed: (a) a reduction of the usual increase of time estimation error with increased ISI; (b) an increase of the subjects knowledge of the ISI range resulting from the discontinuity of the time-marking click which makes easier a discrete time-intervals numbering process; (c) a change of the simple-RT task into a discrimination task.     

A measurement technique for stability as applied in rifle shooting

A technique is described for the measurement, in the field, of stability and steadiness. Apparatus and method are provided along with suggested scoring procedures.