Concomitant Pavlovian conditioning of heart rate and leg flexion responses in the rat

Pavlovian conditioning was studied in male Fischer 344 rats using tones as the conditioned stimulus (CS) and footshock as the unconditioned stimulus (UCS). Different groups of animals received (a) contiguous CS-UCS pairings with a 0.5 sec CS, (b) contiguous CS-UCS pairings with a 4.0 sec CS, or (c) a random sequence of noncontiguous tones and shocks using either a 0.5 sec or a 4.0 sec CS. Heart rate (HR) and leg flexion (LF) responses were recorded. Leg flexion conditioning occurred only in the 0.5 sec contiguous group. Decelerative HR CRs occurred only in the 4.0 sec contiguous group. Accelerative HR changes occurred in the other two groups but were significantly greater in the 0.5 sec contiguous group. These results are similar to but not identical to those obtained during eyeblink or nictitating membrane conditioning in rabbits, and suggest that the topography of the Pavlovian HR CR is dependent on the simultaneous occurrence of other classically conditioned responses.     

Effects of reward on delayed reaction time task performance of hyperactive children

This experiment was designed to investigate the effects of continuous, partial, and noncontingent schedules of reward, as well as the withdrawal of rewards, on the performance of hyperactive and normal control children on a delayed reaction time task. Although noncontingent reward resulted in faster reaction times for control subjects, performance of hyperactives deteriorated under noncontingent reward and improved when it was withdrawn. Also, reaction times of controls during extinction remained superior to baseline, whereas performance of hyperactives returned to baseline level. It was suggested that these and other findings reviewed point to an unusual sensitivity to rewards in hyperactive children.     

Effects of reinforcement on concept identification in hyperactive children

The effects of continuous and partial reward on the performance of hyperactive and normal children on a concept identification task were compared. Because reduction in information feedback is usually associated with partial reward schedules, the study was designed to yield information regarding the contribution of reduced feeback to performance in the partial reward condition. Previous findings of a performance deficit in hyperactives under partial reward were replicated. The findings help rule out an information feedback explanation for this deficit. The authors suggest that a motivational factor involving the elicitation of frustration when expected rewards fail to appear may be responsible for the poor performance of hyperactives on the partial schedule.This research was supported by Grant No. 943-03-34 from the Social Sciences Research Fund, McGill University.     

The proper role of clusters in mathematical models of continuous recall

Previous research has shown that the number of words cumulatively recalled (N) at time (t) is a negatively accelerated function that reaches an asymptote as t → ∞. Research has also shown that the increase in N with t occurs in bursts or clusters. Several models purport to account for this cumulative recall curve in terms of cluster characteristics. The present research shows that previous models have not in fact successfully linked continuous recall to cluster characteristics. This research demonstrates that cluster models need to employ three empirical characteristics of clusters: T_b, the time between clusters; T_w, the average time between words within a cluster; and W_c, the number of words within a cluster. It is shown that these three quantities determine the cumulative recall curve, and these three quantities may in turn be characterized by four parameters. Of these four parameters, only three actually characterize the cumulative recall curve. Two parameters determine the initial slope and final asymptote of the curve, while a third parameter, which we introduce for the first time, characterizes the curve's shape. This latter parameter may be interpreted as the ratio ofthe time spent in retrieving and discarding a cluster that has been previously recalled to the amount of time spent in retrieving and outputting a newly encountered cluster. It is pointed out that previous success in fitting the cumulative recall data with a two-parameter function may be explained by the fact that this parameter lies in a restricted range about unity. Further experimental work is suggested to elucidate the behavior of this new parameter. Two models are then proposed to account for these characteristics of clusters and the shape of the recall curve.     

Nonmetric maximum likelihood multidimensional scaling from directional rankings of similarities

A maximum likelihood estimation procedure is developed for multidimensional scaling when (dis)similarity measures are taken by ranking procedures such as the method of conditional rank orders or the method of triadic combinations. The central feature of these procedures may be termed directionality of ranking processes. That is, rank orderings are performed in a prescribed order by successive first choices. Those data have conventionally been analyzed by Shepard-Kruskal type of nonmetric multidimensional scaling procedures. We propose, as a more appropriate alternative, a maximum likelihood method specifically designed for this type of data. A broader perspective on the present approach is given, which encompasses a wide variety of experimental methods for collecting dissimilarity data including pair comparison methods (such as the method of tetrads) and the pick-M method of similarities. An example is given to illustrate various advantages of nonmetric maximum likelihood multidimensional scaling as a statistical method. At the moment the approach is limited to the case of one-mode two-way proximity data, but could be extended in a relatively straightforward way to two-mode two-way, two-mode three-way or even three-mode three-way data, under the assumption of such models as INDSCAL or the two or three-way unfolding models.The first author's work was supported partly by the Natural Sciences and Engineering Research Council of Canada, grant number A6394. Portions of this research were done while the first author was at Bell Laboratories. MAXSCAL-4.1, a program to perform the computations described in this paper can be obtained by writing to: Computing Information Service, Attention: Ms. Carole Scheiderman, Bell Laboratories, 600 Mountain Ave., Murray Hill, N.J. 07974. Thanks are due to Yukio Inukai, who generously let us use his stimuli in our experiment, and to Jim Ramsay for his helpful comments on an earlier draft of this paper. Confidence regions in Figures 2 and 3 were drawn by the program written by Jim Ramsay. We are also indebted to anonymous reviewers for their suggestions.     

The fantasy-reality distinction in televised violence: Modifying influences on children's aggression

Fifth-grade and kindergarten boys and girls were exposed to a violent televised episode that was introduced as a fictional portrayal (fantasy condition) or as a news broadcast (reality condition). Additional groups were given no information (no-instructional-set condition) about the violent stimulus or were not exposed to the violent episode (no-TV condition). Aggressive responses and helping responses were recorded immediately following exposure. Boys were most aggressive in the reality and no-TV conditions. They were less aggressive in the noinstructional-set condition and least aggressive in the fantasy condition. In almost direct contrast, girls were most aggressive in the fantasy and no-instructional-set conditions and least aggressive in the reality and no-TV conditions. A posteriori analyses of this interaction effect revealed that girls were less aggressive than boys in the no-TV condition and in the reality condition, but not in the fantasy condition nor the no-instructional-set condition. These effects held for both older and younger children.     

Can Constructive Mathematics be Applied in Physics?

The nature of modern constructive mathematics, and its applications, actual and potential, to classical and quantum physics, are discussed.     

Does the Total Principle have any Repugnant Implications?

On the Total Principle, the best state of affairs ( ceteris paribus ) is the one with the greatest net sum of welfare value. Parfit rejects this principle, because he believes that it implies the Repugnant Conclusion, the conclusion that for any large population of people, all with lives well worth living, there will be some much larger population whose existence would be better, even though its members all have lives that are only barely worth living. Recently, however, a number of philosophers have suggested that the Total Principle does not imply the Repugnant Conclusion provided that a certain axiological view (namely, the 'Discontinuity View') is correct. Nevertheless, as I point out, there are three different versions of the Repugnant Conclusion, and it appears that the Total Principle will imply two of the three even if the Discontinuity View is correct. I then go on to argue that one of the two remaining versions turns out not to be repugnant after all. Second, I argue that the last remaining version is not, as it turns out, implied by the Total Principle. Thus, my arguments show that the Total Principle has no repugnant implications.