Food-searching behavior of cats in a multiple-choice elimination problem

Twelve cats were individually exposed to a four-point elimination problem for 50 consecutive days. The problem for the animals consisted of choosing a series of different points where they found, and were allowed to eat, a piece of meat, without returning to any previously visited point. The order of elimination was not controlled in any way by the experimenter. Results indicated that cats were able to solve this problem. All subjects showed a strong tendency to make successive runs toward points situated as far apart as possible. Moreover, a relation was shown between performance and the tendency to follow this high divergence principle. This result is discussed in terms of subjects' ability to process information about the spatial characteristics of the experimental situation. This ability might in fact be related to the behavioral plasticity of animals in spatial problems according to the difficulty of the task.     

Observation and discrimination learning in the rat: Effects of stimulus substitution

Effects of prior observation of modeling performances upon learning simultaneous visual discriminations were studied in nine groups of rats. Stimulus patterns which had been positive (“Cued”) or negative (“Uncued”) for the model animal and novel stimuli were presented. Observers learned faster if discriminations required approach to, rather than avoidance of, the previously positive stimulus. Approach to the negative stimulus was acquired more rapidly only if the second stimulus was novel. Approaches to a substituted new stimulus combined with either of the previously viewed stimulus patterns required nearly twice the training needed for a similar response attachment when both stimuli were novel. Attentional changes appear to underlie the stimulus control exerted over the observer rat in instrumental learning situations.     

JOHN LOCKE: BETWEEN CHARITY AND WELFARE RIGHTS

In the past quarter century C. B. MacPherson's reading of Locke has enjoyed a wide appeal. We are all by now familiar with Locke as the ardent proponent of possessive individualism, with its accompanying acquisitive tendencies and egoism. To be sure, MacPherson's interpretation has not gone unopposed. Of late it has been challenged in all its fundamentals by the scholarly and ingenious work of James Tully. Far from seeing Locke as providing the theoretical underpinnings for unbridled capitalism, Tully puts forward the view that Locke was sympathetic to the possibility of radical redistributive measures. That is, that he was not in principle opposed to rights to welfare.     

The existence and role of retinotopic and spatiotopic forms of visual persistence

Current theoretical conceptualizations of visual persistence fail to address the issue of its functional role. Based on extant experimental data we tentatively identify two general types of visual persistence: one resides in activity along the afferent visual pathway and is retinotopically organized; the other resides at central levels and is spatiotopically organized. Moreover, whereas the former afferent persistence is eliminated via saccadic suppression mechanisms in order to separate successive, retinotopic frames of pattern information, the latter, central one, in contrast, is generated and enhanced via extraretinal signals accompanying saccades in order to preserve phenomenal continuity of a stable spatiotopic representation of the environment from one fixation to the next.     

Size scaling in two-dimensional pictorial arrays

The study examined effects of instructional sets (objective, phenomenal, projective, and retinal) on the judged sizes of blocks placed at various “distances” in a pictorial array. Magnitude estimations of size were consistent with previous studies of size constancy in three-dimensional arrays. Chronometric analyses indicated that reaction time increased with distal size, but was not affected by perceived distance. The results suggested that size was scaled relative to a perceptual unit. Instructions affected the nature of the scale unit (proximal vs. distal), but not the scaling process itself.     

On misoriented letters

An experiment is reported in which subjects were presented with misoriented letters and asked to identify the transformations to which normal letters had been subjected to produce the misorientation. When two or more transformations were equally justifiable from the geometrical point of view, they did not have necessarily the same relevance from the perceptual standpoint. For instance, it was easier for the subjects to see an upside-down letter R as the outcome of two reflections (one about the horizontal axis and one about the vertical axis) rather than of a 180 degrees rotation in the picture plane. Contrary to expectation, for the same final result a reflection--a movement in three dimensions--was preferred to a rotation--a movement in two dimensions--and two reflections were preferred to a single rotation. To explain the distribution of the responses, a hypothesis on the 'mode of appearance' of equivocally oriented objects is presented. This postulates that the directional axes assigned to the objects tend to remain in correspondence with those of the environment. Moreover, the polarization of the up-down axis tends to be preserved, while that of the left-right axis does not. Implications of this simple model for the perception of misorientations are discussed.     

Contraction,Infinitary Quantifiers,and Omega Paradoxes

Our main goal is to investigate whether the infinitary rules for the quantifiers endorsed by Elia Zardini in a recent paper are plausible. First, we will argue that they are problematic in several ways, especially due to their infinitary features. Secondly, we will show that even if these worries are somehow dealt with, there is another serious issue with them. They produce a truth-theoretic paradox that does not involve the structural rules of contraction.