Perceptual ambiguity and stability of reversible figures

In this work, the results of two experiments on ambiguous patterns are reported, which have been obtained by presenting a series of stimuli designed, in both cases, to reduce gradually the ambiguity of the patterns. Such reduction has been performed by respectively increasing or decreasing the amount of graphic details in the experiments. Data of both experiments show a lengthening of mean reversal time. The increase in the stability of one percept can be regarded as associated with the increasing difficulties encountered by an observer in organizing and restating the alternative "hypothesis" through the perceptual mechanisms. The loss of balance in the durations of percepts is discussed in terms of their different informational contents. Finally, in Exp. 1 an analysis is made to evaluate to what extent an addition of perceptual cues, designed to reinforce a three-dimensional interpretation of a pattern, can influence its figure-ground alternation.     

Function of the blood-cerebrospinal fluid barrier and selected biochemical cerebrospinal fluid components in senile dementias of various types

Some selected CSF and serum components were determined in demental patients classified by the Hachinski test into vascular and primary-degenerative groups. As for the vascular group, the frequency distribution of the serum/CSF albumin ratios characterizing the barrier function corresponds to that of controls, in primary-degenerative cases, however, it is shifted to higher values. In vascular dementia higher CSF LAP activities pointing to actual cell damaging processes in the CNS were found. The concentrations of lactate and some trace metals in CSF and serum are not suitable for differential diagnostic purposes.     

128 Halftone patterns for printing gray-level images on a laser printer

This paper presents a set of 128 halftone patterns on an 8 × 8 block size. The patterns have been designed to produce an acceptable gray-scale rendition when the halftone is seen from a distance and, at the same time, to allow comparisons to be made among the intensity values of individual pixels at a closer look. A Pascal program is also presented that produces halftones on an HP Laserjet+ laser printer, and sample halftones are shown. Finally, a method is proposed that prevents images digitized with a 4:3 aspect ratio from being distorted when halftones are printed at the usual 1:1 aspect ratio.     

Quantitative Analysis of IRT Variability During the First Training Stages of a Variable-Interval Schedule in Rats

Five rats were reinforced under variable-interval schedules with different average interreinforcement intervals (30 seC., 1 min, 2 min, and 4 min). Each animal was run only two sessions of each schedule. The interresponse times (IRTs) were recorded and analyzed. The autocorrelation function of the IRT series and of the IRT time series (number of responses per time interval) were calculated, and absence of periodicity in the subject’s behavior was demonstrated. Frequency distribution of IRTs showed in all cases a similar shape and could be fitted to a gamma probability density function in 60% of cases with a signification level of .01 (Kolmogorov-Smirnoff test). The frequency distributions of the IRT time series were distributed as a Poisson process with a .05 significance level. These results suggest that during variable-interval schedules the responses of the animal can be modeled as a random process characterized by a gamma distribution, as a first approximation.

     

Scores on the State-Trait Anxiety Inventory for children in a longitudinal study of pubertal Spanish youth.

Changes in scores on the State-Trait Anxiety Inventory for Children for a sample of 534 pubertal adolescents were longitudinally studied over a period of 4 years. Biological development and other variables were investigated. For the 310 boys, A-trait scores decreased significantly with age. The 224 girls showed significantly higher scores than boys in all years of the study. No significant relationship was found between anxiety and pubertal maturity. The year-to-year persistence in symptomatology of anxiety ranged between 55.6% and 66.1% for girls and between 48.5% and 53.1% for boys. Girls showed bi- and tri-annual persistence between 31% and 50%, and boys between 13% and 27%. Neuroticism scores formed the best predictor of A-trait scores. Symptomatology of anxiety is not transient during early adolescence, so personality may provide a risk indicator in the development of anxiety.     

The psychoanalytic interview of slum dwellers in Lima

A large, as yet unfinished project conducted by the "Centro Psicoanálisis y Sociedad" concerns the use of psychoanalytic methods in social research. Case excerpts are presented to illustrate typical forms of the subjective processing of migration and marginalization.