Detection and scaling of statistical differences between visual textures

Stochastically textured patterns were used to investigate the sensitivity of Ss to differences in the statistical distributions of locally defined properties of element density and shape. The results of the study indicate that when the textures were most structured, in terms of their variance, Ss were most accurate at detecting dissimilarities between pairs of patterns. Ss also rated the similarity of the statistical distributions of elements of patterns differing in local properties. Multidimensional scaling analysis of the ratings showed two dimensions, representing monotonic orderings of the stimuli.     

PSYCHOPHYSIOLOGICAL REACTIONS TO TWO DIFFERENT PLACEBO TREATMENTS

Reactions to a placebo introduced either as a depressant or as a stimulant drug were examined in 16 healthy female subjects. Comparisons between pre- and post-placebo measurements showed that the two treatments produced marked effects in opposite directions: (1) the 'depressant' placebo produced a statistically significant decrease in pulse rate, blood pressure, objective and subjective reaction speed, as well as significant effects on subjective mood in the expected directions, and (2) the 'stimulant' placebo produced opposite and significant changes in all variables. The subjective reactions were, on the whole, more pronounced than the effects on performance and physiological functions.     

Effects of pentobarbital on fixed-ratio reinforcement,

Certain doses of pentobarbital consistently increased the rate of pecking engendered by a fixed-ratio schedule of 30 responses in a group of 13 pigeons, and still higher doses produced decrements in rate of responding. For individual subjects, the dose-effect functions were qualitatively similar, but differed with respect to the doses producing the maximum increase and subsequent decrease in rate. In general, the maximum occurred at lower doses and the decrement was greater at the highest dose in the birds with the highest control rates. It was also possible to distinguish between the effects of pentobarbital and several other drugs on the behavior maintained by FR 30. The results indicate that changes in rate of responding on FR 30 after drug administration are dose-dependent, drug-specific effects.     

Generalization of auditory intensity as a function of small amounts of discrimination training

Rats were trained on a two-valued auditory-intensity discrimination for 5, 2, 1 or 0 days. Then, the bar-press response rate was sampled in the presence of seven added discrimination stimuli (generalization) for seven days. Daily training sessions were 4 hr in length throughout the experiment. Only the five-day group exhibited a marked superiority on the multi-valued discrimination when contrasted with the group having had no prior simple discrimination training.     

The effect of two schedules of primary and conditioned reinforcement

Of 23 pigeons, 11 received continuous reinforcement for key pecking, and 12 received an FR 10 schedule of reinforcement. The birds were then tested without food, but with potential conditioned reinforcers presented either on the same schedule as in training, on the other schedule, or not at all. Each bird in the subgroup trained on CRF and tested with S^r's at FR 10 not only gave more responses in testing than did each bird in both subgroups receiving no S^r's, but also gave more responses than did each bird in the S^r subgroup receiving CRF training and S^r's at CRF. Cumulative records are presented to show the effects of different schedules of conditioned reinforcers.