The detection of visual intensity differences by pigeons

Pigeons were trained in a conditional discrimination procedure to discriminate between visual stimuli that varied in intensity. The magnitude of the intensity difference ranged from 0.80 to 0.05 logarithmic units. Psychometric functions were calculated from the data and the mean difference threshold for the 11 subjects was approximately 0.12 logarithmic units. A signal-detection analysis of the data suggested that stimuli that were below the calculated threshold were detectible to the subjects.     

Negation of Park's transformations

Zusammenfassung Parks Kritik beruht, meiner Ansicht nach, auf einem entscheidenden Mißverständnis meiner Intentionen: es geht mir überhaupt nicht um eine Argumentation gegen eine Transformationsgrammatik à la Chomsky, und nicht einmal in erster Linie gegen die Absicht mancher Psycholinguisten, eine derartige Theorie in ihren psychischen Funktionen aufzuzeigen. Ich möchte lediglich dafür plädieren, daß die Psycholinguistik in erster Linie psychologische (und nicht linguistische) Überlegungen und Modellvorstellungen als Leitlinien verwendet.     

An extinction-induced increase in an aggressive response with humans

Nine subjects, 14 to 18 yr old, pulled a knob on a schedule of monetary reinforcement. Concurrently, they escaped or avoided periodic presentations of a tone by pressing a button that required 1.5 lb (6.67 N) of force or by punching a padded cushion that required 20 lb (88.96 N) of force. The punching response was designated as an aggressive response because the force of this response together with its topography was comparable to responses of humans that deface objects and produce escape or counter aggression from other humans. It was found that button pressing was the preferred concurrent avoidance response and there were few punches. However, when the monetary reinforcer was discontinued (extinction) punching increased for seven of the nine subjects, but there was no consistent change in the rate of button pressing. When the punching response was replaced by another non-preferred but non-aggressive response, neither this response nor button pressing increased during extinction. Hence, the increase in punching during extinction cannot be attributed solely to the fact that it was a concurrent response or a non-preferred response.     

Punishment of shock-induced aggression

Squirrel monkeys were restrained in a chair equipped with a tail-shock apparatus and a pneumatic bite hose located in front of the subject's face. An aggressive response was recorded when the monkey bit the hose. Initial sessions in which no shocks were delivered produced some biting. When biting during these sessions stabilized at a near-zero level, regularly scheduled shocks were delivered to the monkey's tail, causing a consistently higher rate of biting. After several sessions under these conditions, a punishment phase was introduced in which the previous shock conditions were maintained, and every bite was followed immediately by another, more intense shock. Biting under these conditions was suppressed to a near-zero level. When the punishment contingency was removed, biting increased. With one subject, two additional bite-contingent stimuli were examined: (1) a milder shock that, when made contingent upon hose biting, also suppressed that response, and (2) a contingent tone that had no obvious suppressing or facilitating effect. Individual differences among subjects were extreme, but the effect of bite-contingent shock was consistent. Observations of the subjects during the punishment sessions indicated the existence of certain side effects that resulted from the use of punishment to suppress shock-induced aggression.     

Disruption of a temporal discrimination under response-independent shock

The responding of rats was reinforced on one key after a 1-sec auditory stimulus and on a second key after a 5-sec stimulus. With errors punished by a short timeout, all subjects achieved a high level of accuracy. A chain of responses during the stimuli mediated the performance so that when the auditory signals were omitted accuracy decreased only slightly. Response-independent aversive stimulation superimposed upon this procedure both suppressed the total amount of behavior and reduced the accuracy of the discriminative performance, the intensity of the stimulus determining the error rate. The increase in errors under these conditions may have depended in part upon differential suppression of members of the response chain, but such suppression was not necessary, since error rate increased even in its absence. Furthermore, the locus of response disruption within the chain was not consistent from day to day either for any individual animal or across animals.     

A general approach to confirmatory maximum likelihood factor analysis

We describe a general procedure by which any number of parameters of the factor analytic model can be held fixed at any values and the remaining free parameters estimated by the maximum likelihood method. The generality of the approach makes it possible to deal with all kinds of solutions: orthogonal, oblique and various mixtures of these. By choosing the fixed parameters appropriately, factors can be defined to have desired properties and make subsequent rotation unnecessary. The goodness of fit of the maximum likelihood solution under the hypothesis represented by the fixed parameters is tested by a large samplex ² test based on the likelihood ratio technique. A by-product of the procedure is an estimate of the variance-covariance matrix of the estimated parameters. From this, approximate confidence intervals for the parameters can be obtained. Several examples illustrating the usefulness of the procedure are given.This work was supported by a grant (NSF-GB 1985) from the National Science Foundation to Educational Testing Service.