Further evaluation of prompt density,rate of reinforcement,and the persistence of manding

Previous research has evaluated the effects of prompt rates on the rate of communicative behavior. More recent research has suggested that dense prompting can result in communicative behavior that is more resistant to change. However, existing research has not considered the impact that higher response rates had on reinforcement rate, a variable known to impact response persistence. The current study systematically replicated previous research by evaluating communicative responding in contexts associated with dense- and lean-prompt schedules and extended existing research by (a) holding reinforcement rates similar across the two prompting schedules (lean and dense), and (b) evaluating the persistence of communicative responding in the contexts associated with each prompting schedule. The results for Experiment 1 clearly replicated and extended previous research. The results for Experiment 2 were equivocal and suggested that previous reinforcement history and response class size impacted outcomes.     

The free classification of analyzable and unanalyzable stimuli

The free classification of two-dimensional analyzable and unanalyzable stimuli was investigated. Analyzable stimuli consist of dimensions which are distinct and phenomenally separable (e.g., colored geometric forms); unanalyzable stimuli consist of two dimensions which are not distinct, not phenomenally separable, and which are probably perceived as a unitary dimension (e.g., Munsell colors). In the first experiment, Ss judged the similarity between each stimulus pair for both types of stimuli. The results replicated previous work in showing that the city-block metric was appropriate for the analyzable stimuli and that the euclidean metric was appropriate for unanalyzable stimuli. In the second experiment, Ss classified sets of analyzable and unanalyzable stimuli into two or three groups in any way they wished. For analyzable stimuli, classification was based on the dimensional structure-stimuli which alter the dimensional structure by defining another dimension change classification. For unanalyzable stimuli, classification was based on the similarity structure-stimuli which alter the similarity structure change classification.     

A method for the precise switching of speech

A simple procedure by which a speech signal may be switched on or off (or from one ear to the other) at a precise instant of time is described. The speech sample is first recorded on a magnetic tape loop. A reference pulse is then recorded preceding the speech signal. This reference pulse triggers an adjustable time delay which in tum operates an electronic switch at an appropriate time.     

A device for the easy administration of volatile anesthetics to rats undergoing stereotaxic surgery

Conventional procedures do not provide a practical method for the administration of volatile anesthetics such as halothane to rats while they are undergoing stereotaxic surgery. This paper describes a device which meets this need and which is easy and inexpensive to construct. A two-piece cylinder cut from the mouth of a polyethylene bottle forms a closed system around the muzzle of a rat and does not interfere with the stereotaxic apparatus or with the operation itself. The cylinder is attached to any standard device for the dispension of volatile anesthetics. The immediate advantage is that behavioral assesaments can be made relatively soon after surgery.     

Functional equivalence between same-different classifications and judged similarity of Markov patterns

This experiment represented an initial at tempt at comparing same-different classifications and similarity judgments of Markov histoforms sampled from three different schema families. A measure of individual stimulus variability was more strongfy related to classification responses than to judged similarity. Dichotomous responses, derived from the similarity data by imposing threshold criteria, were found to be highly similor to real classification responses when the threshold values were estimated directly from the latter; little correspondence, however, was obtained using optimal classification criteria. The results support the notion that somewhat different features are used in making classification responses and similarity judgments, and indicate the need for developing more sensitive tasks involving controlled scanning of pattem information.     

Visual and tactual form discrimination: Psychophysical comparison within and between modalities

Intermodal perceptual equivaience was investigated, using visual and tactual oddity discrimination and cross-modal matching-to-sample tasks. Four groups of Ss were presented with 100 problems made up of randomly derived forms from five levels of sidedness. The same quadratic relationship was observed for all tasks as a function of complexity, with optimal performance at eight sides. Comman information utilization, as indicated by intercorrelations of performance variables and by correlational analyses with differences in form measures, was not as pronounced within side classes. Evidence concerning the nature of pattern-feature usage in discrimination was obtained from graphical analyses.     

Schematic concept formation: Feature measures and constraint redundancy as predictors

Constraint redundancy (R_c) was varied in order to manipulate the statistical structure of sets of patterns. Measures of pattern features and R_c were related to the categorization by Ss who had experienced different types of preexposure to sets of patterns from the same stimulus domain. Both R_c and pattern measures were related to the categories produced by Ss in a schematic-concept-formation (SCF) task.     

Recognition assessed by D' and by a non-parametric alternative (the A-index) as a function of the number of choices

Freedom from restrictive assumptions and ease of psychological interpretation are two basic criteria for a satisfactory measure of recognition performance. The A-index (Brown, 1965a) comes close to fulfilling these criteria. It is based on the proportion of wrong choices rejected in a multi-choice test as revealed by the number of choices required to select the correct choice. It can be transformed into the d' measure of signal detection theory (SDT) if the standard assumptions of this theory hold, but not in general. Two experiments on the recognition of words-in-noise are described. In the first there were 3, 5, 8 or 16 choices. They were typed on a card which was displayed to the listener during the presentation of a word. On both measures 5-, 8- and 16-choice recognition did not differ significantly, while 3-choice recognition was slightly, but significantly, superior. The second experiment concerned the effect of delaying the display of the card until 2 sec. after presentation. No evidence for an effect was obtained. In both experiments, there was suggestive but not conclusive evidence that the d' measure tended to overestimate recognition efficiency.     

Selective eye movements to simultaneously presented stimuli during discrimination

Human Ss, when given a discrimination task whose stimuli varied in dimension and relevance, always chose and ftxated more frequently the stimulus they had been reinforced for choosing. Decreasing the brightness reduced the choice and ftxation preference for form stimuli over line stimuli and raised total ftxation frequency. Ss decreased fixation frequency to discriminanda with practice.