On Russell's principle of induction

An improvement on Horwich's so-called pseudo-proof of Russell's principle of induction is offered, which, we believe, avoids certain objections to the former. Although strictly independent of our other work in this area, a connection can be made and in the final section we comment on this and certain questions regarding rationality, etc.The authors would like to thank the two anonymous referees and Jeff Paris for their helpful and encouraging remarks. It goes without saying, of course, that the responsibility for any further errors, ambiguities or whatever, is entirely ours.We would also like to acknowledge the support given by the Centre of Logic. Epistemology and History of Science of the University of Campinas and, in the case of French, the Brazilian Council for Scientific and Technological Development (CNPq), in the preparation of this work.     

Immobility reactions: A modified classification

This theoretical paper sets the stage for subsequent experimental reports on mobility and immobility in the Arkansas Line of Nervous Pointer dogs as contrasted with kennel mates of the normal line. Exactly opposite to the normal animals, the nervous dogs show marked inhibition of heart rate and musculoskeletal responses to man, including reduced ambulation and durable immobility following inversion and brief manual restraint in an open sling. The sling immobility of the nervous dogs (which may not differ basically from their freezing in upright position) might be designated as “tonic immobility” (TI). We hypothesize that such immobility, common in laboratory and natural conditions in many species, should be divided into two classes: hypotonic (cataleptic) and hypertonic (catatonic). We provide examples of such behaviors, particularly in man and dog, and cursorily review TI studies of other species. Neurophysiologic and neurochemical studies which bear on possible immobility mechanisms are briefly noted. We suggest that inconsistencies in reported concommitants of TI might result from failure to discriminate between types of behavioral responses.     

Successive-beat analysis of cardiovascular orienting and conditional responses

We have shown that prominent changes in heart rate (HR) and blood pressure (BP) occur in dogs during classical defensive conditioning. These changes are usually analyzed as average HR and BP during control periods versus averages during conditional stimulus (CS) and unconditional stimulus (US) periods. A new method has been developed for evaluation of these functions, viz., analysis across many trials of successive beats beginning at onset of CS and working backward (control period) and forward (CS period). Nine awake dogs were continuously studied: six with HR and intra-arterial BP measurements and three with HR measurements only. A drop in HR occurs 1 to 2 beats after CS onset (often noted as a “dropped” beat on individual trials). In some dogs, on the third to fifth beat HR reaches its maximum during the CS period, thereafter falling slightly, but still above baseline; other dogs show progressively increasing HR throughout the whole CS period. At US onset (foreleg shock) HR usually rises rapidly to a peak greater than that at CS maximum. BP follows HR changes fairly closely, diastolic better than systolic. These results indicate that I) this method can reveal transients previously unsuspected, 2) a prominent initial sudden bradycardia followed by tachycardia commonly occurs in conditioning in dogs, 3) the latent period of prominent HR increase is usually quite short (1.3 to 1.6 secs.), and 4) BP follows HR directly during the early part of the CS.     

Psychogenic vagotonia in a family of beagle dogs

Eight inbred beagle dogs, litter mates of two generations, exhibited psychogenic vagotonia (long sinus pauses and transient atrioventricular block of the heart) during orienting to tones. This was intensified during tones following “one-trial conditioning” to a single painful leg-shock. It was potentiated during conditional stimuli (CS+) regularly reinforced by leg-shock; whereas unreinforced tones (CS?) elicited less vagotonia. Additional evidence of differentiation was observed in one dog when the differential magnitudes of the responses were reversed following reversal of the significance of the conditional stimuli. The possible mechanisms of these changes and correlations with clinical material are discussed. Results of this study illustrate the interplay between constitutional predisposition and psychological factors in prominent cardiovascular changes.     

The Logic of Pragmatic Truth

The mathematical concept of pragmatic truth, first introduced in Mikenberg, da Costa and Chuaqui (1986), has received in the last few years several applications in logic and the philosophy of science. In this paper, we study the logic of pragmatic truth, and show that there are important connections between this logic, modal logic and, in particular, Jaskowski's discussive logic. In order to do so, two systems are put forward so that the notions of pragmatic validity and pragmatic truth can be accommodated. One of the main results of this paper is that the logic of pragmatic truth is paraconsistent. The philosophical import of this result, which justifies the application of pragmatic truth to inconsistent settings, is also discussed.     

Assessment of pointer dog behavior

Studies of behavioral traits of the “Arkansas Line of nervous pointer dogs” are well documented (Murphreeet al., 1969). Demonstrations of drug effects on these traits, as measured on the standardized behavior test and expressed as “Morbidity Score,” have been disappointing, despite other evidence of effectiveness of drug treatments such as modification of operant performance (Murphreeet al. 1974c). A simple reproducible test with high interrater reliability is presented here. Subjects were nine nervous dogs that received placebo, pimozide, and chlordiazepoxide in a double-blind crossover design. Both drugs significantly attenuated “human avoidance,” a nervous trait. Placebo had no effect. The chlordiazepoxide effect was maximal on the first day of administration, returning to baseline three to four days after the last dose. The pimozide maximal effect was on day 4, with return to baseline six to nine days after the last dose. In addition to the aberrant behavior of the nervous pointer, hyperresponsiveness to dopaminergic stimulation and increased levels of L-DOPA in the cisternal spinal fluid were observed.