Bill R. Brown

Schematic concept formation as a function of constraint redundancy and knowledge of results

The present study assessed the joint effects of schematic redundancy (Rc) and knowledge of results (KR) on performance of a modified oddity task requiring the assignment of stimuli to categories corresponding to three different schema families. A high level of Rc (70%) facilitated schematic concept formation (SCF); a low level of Rc (40%) prevented the occurrence of SCF, but didactic concept learning did occur at this level if KR was provided.

Free sorting with stimuli clustered in a multidlmensional attribute space

An experiment was conducted to determine whether Ss leam, without knowledge of results or prior familiarization with the prototypes, to sort histoform stimuli generated by three probablistic rules into categories consistent with these mies. Seven Ss were asked to sort 30 stimuli (10 from each schema population) on each trial. No constraints were placed on the number of categories to be used. A statistic was developed to measure consistency between schema-defined categories and subjeet-defined categories. Four of the seven Ss met the leaming criterion, and demonstrated increasing consistency with the schema-defined categories across trials. In general, more categories than necessary were used to classify the stimuli correctly. The results raise several questions about classification strategies used by Ss in perceptual learning tasks with stimuli generated by probabilistic rules, and indicate the need for further research conceming the variables that influence perceptual category formation.

Perceptual learning in pattern discrimination tasks with two and three schema categories

This research demonstrated that humans can develop the ability to distinguish between stimuli of either two or three schema families without externally administered knowledge of results or prior familiarization with the population prototypes. These demonstrations of schematic concept formation support the perceptual learning theory that differentiation of higher order variables can occur on the basis of information derived from perceiving the stimuli, and indicate the need for further investigation of the detailed conditions under which the phenomenon occurs.

Magnitude estimation of perceived distance over various distance ranges

Three groups of Os made magnitude estimation judgments of the apparent distance of a stationary space vehicle model under conditions simulating outer space. Psychophysical functions for three stimulus ranges were obtained. The exponents for the near and far stimulus ranges were 1.0. The power function exponent for the “full” range group was 0.48. The psychophysical scales were compared to JND scales obtained in previous research. The results indicated that in all ranges investigated the power law is an appropriate description of the relationship between perceived and objective distance, but that distance range and the location of the range are important determinants of the psychophysical scale.

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.

Evaluation of unconstrained sorting data

Two statistics are offered for evaluating unconstrained sorting performance in a specific task when categories are E-defined. One statistic is based upon empirically estimated sampling distributions and can be used for determining sorting performance significantly deviant from chance for any number of S-defined categories; the second statistic can be used to evaluate consistencies between S- and E-defined categories, regardless of the number of categories used by S. The present procedure provides a statistical basis for evaluation of performance where no adequate evaluation procedures are now available.

Discrimination among schematic stimuli as a function of response mode, constraint redundancy and form of Markov rule

This experiment demonstrated that Ss can successfully discriminate among VARGUS 7 stimuli having different central tendencies. Moreover, neither same-different classification responses nor similarity judgments varied as a function of the particular Markov prototypes used in the discrimination task. The results thus suggest that the three prototypes were equally encodable, and that the schema clusters were subjectively equidistant, regardless of the amount of noise introduced into the stimuli.

Distance discrimination in a simulated space environment

The just noticeable difference (JND) for distance was investigated by a paired-comparisons method using successive comparisons. The research utilized an optically simulated large target located in a textureless environment at distances along the saggital plane out to 12, 800 ft. The value of ΔD/D varied from less than 3% at 200 ft to about 7% at 12, 800 ft. The results confirmed a power function relationship between distance threshold and observation distance.

Concept formation as a function of perceptual pretraining and knowledge of results

The present study assessed the joint effects of perceptual pretraining (PT) and knowledge of results (KR) on performance in a task requiring discrimination among stimuli sampled from three different schema families. Neither schematic concept formation (SCF) nor didactic concept formation was significantly influenced by increasing the amount of pretraining. Didactic concept formation occurred if KR was provided, but the low level of stimulus redundancy in the task prevented the occurrence of SCF.