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.     

Factor analysis for clustered observations

Classical factor analysis assumes a random sample of vectors of observations. For clustered vectors of observations, such as data for students from colleges, or individuals within households, it may be necessary to consider different within-group and between-group factor structures. Such a two-level model for factor analysis is defined, and formulas for a scoring algorithm for estimation with this model are derived. A simple noniterative method based on a decomposition of the total sums of squares and crossproducts is discussed. This method provides a suitable starting solution for the iterative algorithm, but it is also a very good approximation to the maximum likelihood solution. Extensions for higher levels of nesting are indicated. With judicious application of quasi-Newton methods, the amount of computation involved in the scoring algorithm is moderate even for complex problems; in particular, no inversion of matrices with large dimensions is involved. The methods are illustrated on two examples.Suggestions and corrections of three anonymous referees and of an Associate Editor are acknowledged. Discussions with Bob Jennrich on computational aspects were very helpful. Most of research leading to this paper was carried out while the first author was a visiting associate professor at the University of California, Los Angeles.     

The circle as a model for the interpersonal domain of Swedish trait terms

Swedish interpersonal traits were assumed to have the structure demonstrated by Wiggins for the Interpersonal Adjective Scales in English. Positive and negative interpersonal trait terms were rated for accuracy when describing people. The ratings were used to construct 16 eight-item scales which were ordered relative to two principal components and labelled A to P. The evaluative meaning of each scale item was rated by a second group. The ranks of the mean ratings for the scales followed expectations. The 16 scales were combined into eight scales PA, BC, DE, etc., to NO. From a new group of subjects (N = 159) self-ratings were obtained. The correlations between the eight scales were used to obtain maximum-likelihood estimates of population coefficients of a hypothetical circulant matrix. A circumplex model fitted the data well and the two equally large orthogonal components ordered the PA to NO variables within a circular semantic space. The model was interpreted as a structural representation of basic-level categories for interpersonal attributes of personality in the natural language.     

High Level of Footshock during Inhibitory Avoidance Training Prevents Amnesia Induced by Intranigral Injection of GABA Antagonists

Disruption of synaptic activity of a number of cerebral structures (e.g., neostriatum, amygdala, and thalamus) produces marked deficits in retention of instrumentally conditioned behaviors. When animals are given a relatively high number of training trials or high intensities of footshock during learning, however, such disruption is considerably less effective. Since there is a close anatomical and functional relationship between the neostriatum and the substantia nigra, it was of interest to determine whether enhanced training with a high level of footshock would prevent the reported amnesic state induced by injections of GABA antagonists into the latter structure. Rats were trained in a one-trial inhibitory task, using 0.2 or 0.4 mA, and then injected with microgram quantities of picrotoxin or bicuculline into the substantia nigra and posterior region of the zona incerta; retention was measured 24 h later. Only those groups that had been injected into the nigra and trained with 0.2 mA showed amnesia. These results support the hypotheses that (a) the normal activity of a set of structures is essential for the development of memory consolidation and (b) after an enhanced learning experience these structures may participate in memory consolidation, but are not necessary for the occurrence of this process.     

Therapeutic factors in interactional inpatient groups: Results from a Turkish sample

Therapeutic factors in an inpatient group from Turkey are presented. A total of 40 patients were seen over a period of 2 years and each patient was given Yalom's (1983) 60-item therapeutic factor list on discharge. The first four most valued therapeutic factor groups were Catharsis, Existential Factors, Cohesiveness and Hope. There were significant differences in the highly valued factors in different diagnostic groups. Patients with diagnoses of anxiety/somatization and borderline/identity problem preferred factors resembling those in many out-patient studies. The results are discussed in the light of relevant literature.