Fixed-interval schedules of intravenous cocaine presentation in rats

Fixed-interval schedules of intravenous cocaine presentation were examined as a function of injection dose (0.32 to 0.64 mg/kg) and interval duration (200 to 400 sec) in two rats. Cocaine was found to exert a dose-related temporal control over the initiation of responding that was unaffected by the fixed-interval contingency. Fixed-interval pause duration was linearly related to injection dose and was the same duration as the interresponse time found on continuous reinforcement schedules of cocaine presentation. The fixed-interval pause remained constant with changes in interval duration. Characteristic fixed-interval patterns of responding were observed. However, overall response rates were inversely related to injection dose and directly related to interval duration. Running response rates varied unsystematically with both variables. These findings are at variance with results typically found in studies of fixed-interval food and electric shock presentation.     

Operator behavior in a dynamic visual signal detection task

The effects of changes in signal-to-noise ratio (SIN) and feedback state on the operator’s detection behavior, particularly derived operator thresholds, were investigated using a discrete visual signal. It was found that: (1) the operator behaves as if he has established different thresholds as a function of S/N; (2) his decision thresholds are relatively independent of the presence or absence of feedback; and (3) the operator will change his threshold accordingly for a change from one S/N to another. A model of the operator’s behavior, which introduced the concept of “operator” noise. yielded predictions of detection and false alarm probabilities which were extremely close to the observed values.     

Aspects of language pragmatics and the social perception of lying

Two experiments were conducted in order to examine the influence of linguistic and extralinguistic variables on the attribution of lying. In the first experiment, one of two tape recordings of a target person, who responded either true or false to a list of adjectives, was evaluated by 83 subjects. The subjects' task was to attempt to discover when the target person was not telling the truth. The stimulus tapes were constructed such that the time between the adjective and the target person's response was systematically varied and the adjectives varied on the likability of a person possessing that trait. Overall, it was found that if the target person responded either too quickly or too slowly the subjects attributed his response as a lie more often than if the delay was more intermediate in duration (p<0.01). The adjective likability value in combination with the true or false response of the target person also contributed to the attribution of lying (p<0.01). In the second experiment, the adjectives were rescaled on another dimension thought to influence the attribution of lying: the degree to which the adjective is true of the general population. The results suggest that this new scale is related to the degree to which lie attributions are made.This research was supported in part by the National Institute of Child Health and Human Development under Research Grant 1 P01 HD-01762-01 and the National Institute of Mental Health under Research Grant MN 08260.