“Impossible figures” and interpretations of polyhedral figures

The concept “impossible figure” is analyzed by formalizing the interpretations of a polyhedral figure by an observer, and defining several types of inconsistency in such interpretations. Tests for these inconsistencies are developed using simple graph theory, and a sufficient condition is established for the feasibility of an interpretation. Finally, techniques are derived for the automatic construction of usual or unusual multibar figures.     

A biased random walk model for two choice reaction times

This paper generalizes Stone's (1960, Psychometrika 25, 251–260) random walk model of two choice response times (RTs) that is based on the sequential probability ratio test (SPRT) and that predicts equal correct and incorrect RTs to the same response. The generalized version allows a bias of the type found in signal detection theory to enter directly into the accumulation process so that ambivalent evidence may be seen as slightly favoring one alternative. The resulting biased SPRT model can predict any relation between correct and incorrect mean RTs. In particular, unlike the special symmetric case of Link and Heath's (1975, Psychometrika 40, 77–105) relative judgment theory (RJT), the biased SPRT model can predict that correct mean RTs are faster for one response but slower for the other. The biased SPRT model, the classical SPRT model, and the symmetric RJT model are all fit to the data of an RT deadline experiment reported by Green and Luce (1973, Attention and performance, New York: Academic Press) and it is shown that, of the three, the biased SPRT model provides the best account. Finally, a method for incorporating the same sort of bias into RJT models is sketched out.     

The development of handedness and dichotic ear listening asymmetries in relation to school achievement: A longitudinal study

To assess the development of dichotic ear asymmetries and handedness, 208 male school children were evaluated in kindergarten and at Grades 2 and 5 (ages 66, 92, and 130 months of age, respectively) with a dichotic listening task and a hand preference test. The Wide Range Achievement Test (WRAT) also was administered at each of the three grade levels. There was significant variability in handedness scores over time only for those subjects whose scores at initial testing, that is, in kindergarten, identified them as non-right-handers. Both right and left handers had a significant increase in dichotic listening scores over time; however, only right handers had a significant right ear advantage at each evaluation. Regression analyses showed that combined hand preference scores and ear recall scores at each probe when combined accounted for almost 44% of the variance in WRAT achievement scores at Grade 5. Ear asymmetry scores, however, were not predictive of school achievement.     

On unpredictability as a causal factor in “learned helplessness”

In two replications, two groups of dogs were exposed to a series of uncontrollable, electric shocks. For one group the shocks were preceded by a tone (i.e., Paired). For the other group the shocks were randomly related to the tones and hence unpredictable (i.e., Random). Each replication also included a third group; in the first it was exposed only to the series of tones (CS-only), while in the second, it was exposed only to a series of shocks (Shocks-only). Then, all dogs were required to learn a discriminative choice escape/avoidance task in which the required response was to lift the correct paw in the presence of each of two visual S^Ds to escape or avoid the shocks [($\text{S}{}_1{}^{\mathrm{D}}\text{?R}{}_1\text{)}\text{(S}{}_2{}^{\mathrm{D}}\text{?R}{}_2$)]. Dogs preexposed to random tones and shocks were least successful in learning the task relative to those groups which experienced either predicted shocks, only the tones, or only the shocks, which in turn did not differ from each other. These results permitted the inference that the proactive interference with choice behavior following random tone CSs and shocks was attributable to a learned irrelevance generalized with respect to CSs.     

Pavlovian conditioned stimulus effects upon instrumental choice behavior are reinforcer specific

In a transfer-of-control experiment with rats, Pavlovian CSs were tested for the specificity of their effects. The instrumental behavior consisted of a discriminative, conditional two-lever choice task in which qualitatively different appetitive reinforcers were contingent upon the two correct choices. In a Pavlovian phase, subjects experienced conditioning to establish either a CS⁺ or CS^? for one reinforcer or a CS⁺ or CS^? for the other reinforcer. Finally, in a test, these CSs were presented when there was the opportunity to make choice responses. The CS⁺s evoked choices of the lever which had eventuated in the reinforcer that had served as the Pavlovian US, while the CS^?s showed only a slight tendency to evoke the other choice responses. When the CSs were compounded with the original S^Ds, the CS⁺s had little effect upon the vigor of responding while the CS^?s reduced the vigor of responding to the S^D for the reinforcer that was the same as the US used in establishing the CS^?. The results are discussed in terms of associative mediational theory and the reinforcer specificity of Pavlovian conditioned excitation and inhibition.     

Pavlovian processes do mediate control of the “advance” response strategy

Two parallel experiments used pigeons in a transfer of control design to determine the basis of the transfer of the use of the “advance strategy” across successive discriminations (W. K. Honig & H. Lindsay, Learning and Motivation, 1975, 6, 157–178). Pigeons were first trained under instrumental contingencies to use an “advance” response to maximize their exposure to S^D and minimize their exposure to S^Δ. Then orthogonal stimuli (key lights in Experiment 1 and diffuse illuminations in Experiment 2) were independently established through separate discriminative Pavlovian procedures as CS+ and CS? or as CS^o's. Later in special tests, it was demonstrated that the associative values of the Pavlovian CS's were a major factor governing the use of the advance strategy: only pigeons exposed to $\text{CS+}\text{CS?}$ used the advance response to regulate their exposure to either CS. Although these experiments showed that the necessary and sufficient conditions for utilization of the advance strategy are the Pavlovian associative values of the discriminative stimuli, opportunity for differential “operant” responding during the discriminative stimuli seems to be a contributor to the optimal use of the advance response across successive discriminations.     

A study of language functioning in Alzheimer patients

Language functioning in Alzheimer's disease is reviewed and the performance of 25 Alzheimer patients on a standard battery is reported. All these hospitalized patients were aphasic to some degree. As a group, they differed from normals on all language variables, and from stroke patients in terms of higher fluency and lower comprehension. Spontaneous speech showed high incidence of circumlocutions and semantic jargon, but no phonemic paraphasias or target approximations. Syllabic perseverations, shouting, inappropriate laughter, and mutism were late-appearing features. Transcortical Sensory, and Wernicke's aphasias were frequent, but Broca's and Transcortical Motor aphasias notably absent. Extent of language impairment correlated with current length of hospitalization but not age. Reading, writing, and performance scores except praxis, were lower than oral language scores. Findings were discussed in relation to previous results, methodology, and language organization in the brain.