Verbal retention after shadowing and after listening

Ss shadowed or listened to stories that had been recorded at 1 word/sec (wps), 2 wps, and 3 wps. They then took tests of word recognition, semantic retention, and syntax recognition. At the slowest rate, shadowers’ word recognition and semantic retention were somewhat higher than listeners’ scores, but this difference disappeared at faster rates. Significant positive correlations among all three retention scores were observed for listeners, but for shadowers word recognition was unrelated to either of the other two retention measures. The results are discussed in terms of monitoring during shadowing. Implications for experiments on selective attention are considered.     

On the measurement of reinforcement frequency in the study of preference

In a two-link, concurrent-chain schedule, pigeons' pecks on each key during the initial link occasionally produced a terminal link, during which only that key was operative. Responses in the terminal link were reinforced with food on either fixed-interval or variable-interval schedules. In one experiment, relative amount of responding in the initial link equaled the relative harmonic rate of reinforcement in the terminal links. In a second experiment, the selection of interreinforcement intervals in variable-interval schedules in the terminal links was such that rates of reinforcement based on the harmonic or on the arithmetic means of the interreinforcement intervals predicted opposite preferences in the initial links. The observed preference was consistent with that predicted by the harmonic rather than by the arithmetic rates of reinforcement.     

The interaction of veracity and syntax in the processing of sentences1

The reaction times of 80 Ss in judging sentences true or false with respect to pictures were analyzed, and it was noted (a) that true sentences containing an expected surface structure required less time than false sentences of the same structure, (b) that latencies to true sentences containing an unexpected surface structure were longer than latencies to the same sentences when their structure was identical to that of previous sentences, and (c) that transitive-verb constructions appeared easier to judge than predicate nominatives of the same length.     

Statistical methods for absorbing Markov-chain models for learning: Estimation and identification

General algorithms for computing the likelihood of any sequence generated by an absorbing Markov-chain are described. These algorithms enable an investigator to compute maximum likelihood estimates of parameters using unconstrained optimization techniques. The problem of parameter identifiability is reformulated into questions concerning the behavior of the likelihood function in the neighborhood of an extremum. An alternative characterization of the concept of identifiability is proposed. A procedure is developed for deciding whether or not this definition is satisfied.This research was undertaken within the Institute for the Study of Intellectual Behavior, University of Colorado, and is Publication No. 42 of the Institute. The work was supported by NSF Grant GB-34077X. The logic underlying Algorithm I was suggested by Clint Schumacher.     

Determination of CIE chromaticity coordinates of colored lights produced by a projection color mixer

A procedure for measuring the CIE chromaticity coordinates which avoids some of the problems encountered with the method reported by Murch (1972) is described.     

Detection of temporal gaps within and between perceptual tonal groups

Two experiments were conducted to explore the hypothesis that tones widely separated in frequency are processed in separate communication channels. Listeners attempted to detect brief temporal gaps between items in a simple tonal sequence of two high tones followed by two low tones. Temporal resolution within both the high and low groups was near perfect; between-group detection scores were significantly lower. Results are interpreted as evidence for a processing time delay when shifts of focal attention occur between perceptual structures organized within the frequency domain.     

Some acute effects of d-lysergic acid diethylamide on the rat

There is a wealth of literature available on the psychosis-like effects of very small doses of d-lysergic acid diethylamide (LSD-25) in human subjects. It is reported that the drug produces profound changes in emotional behaviour, feelings of depersonalization, visual and auditory hallucinations, catharsis-like episodes and slight changes in autonomic nervous system activity.

The present experiment investigates the possibility of relating the behavioural disturbances induced by LSD-25 to known physiological data. Variation in the latency and running times of trained albino rats is examined. It is demonstrated that latency scores are directly affected by the cerebral concentration of the drug; and that sensory thresholds appear to be raised. It is further shown that when the level of stimulation is raised the rats appear to behave normally.