Manipulation of response-contingent unconditioned-stimulus intensity in human eyelid conditioning: A two-phase model analysis

Four groups of human subjects were given 360 classical eyeblink conditioning trials. All groups received the same UCS (unconditioned stimulus) intensity on[Formula: see text] (nonconditioned response) trials but differed in the intensity presented on CR trials. Response probability increased as a positive function of UCS intensity on CR trials. Phase 1 of the two-phase model was longer when no UCS was presented on CR trials, but did not differ in duration among the remaining three groups. Most subjects could be described with a single operator in Phase 2, the operator limit increasing as a positive function of CR-contingent UCS intensity. For subjects requiring different operator limits on CR and[Formula: see text] trials, the latter was lower with high CR-trial intensities but higher with low CR-trialintensities. The results were interpreted to be more consistent with drive theory than with "law-of-effect" or two-factor theories.     

Skin conductance response conditioning with CS intensities equal to and greater than UCS intensity

With .2-sec bursts of white noise as both conditioned stimulus (CS) and unconditioned stimulus (UCS), conditioning of first-interval skin conductance responses was obtained when the intensity of the CS equaled and exceeded that of the UCS. There was no evidence that second-interval response conditioning occurred. Nonspecific response frequencies were also affected by the variations in stimulus intensity, this raising some question about typical controls employed in SCR conditioning. There was some evidence that second interval responses were suppressed by the intense CS values. It was concluded that the existence of simple conditioning with a CS/UCS intensity ratio equal to or greater than unity was contrary to the Pavlovian proposition that a CS must be biologically less salient than the UCS in order for conditioning to occur. It was noted, however, that the suppression of second-interval responses might indicate that anticipatory CRs which are not confounded with orienting reflexes are prevented from exhibiting a conditioning effect when a high CS/UCS intensity ratio is employed.     

SCORIT: A computer subroutine for scoring electrodermal responses

Given digitized electrodermal response records sampled at a rate of 20/sec and at a sensitivity level between 140 and 170 ohms, a computer subroutine for scoring skin resistance responses is described. It is designed to score multiple responses on a trial, which makes it particularly suitable for classical conditioning experiments involving long interstimulus intervals. The subroutine returns to the main program response latency, base resistance, peak resistance, and time from base to peak. Since SCORIT is written in FORTRAN IV, it can be employed in virtually any modern central computing facility at costs substantially below those involved in hand scoring.     

A two-phase model account of aversive classical conditioning performance in humans and rabbits

A two-phase model was applied to classical conditioning performance in man and rabbits. During phase 1, response probability remained constant. During phase 2, response probability generally increased, although one operator was sufficient for a majority of Ss and two operators were required for a minority of Ss. The latter Ss exhibited increases in responding after a CR trial and decreases in responding after a non-CR trial. The pattern of parameters was similar for man and rabbits. In man, increases in UCS intensity resulted in a decrease in the duration of phase 1 and an increase in the limit of the operators for those Ss requiring more than a single operator to describe performance during phase 2. The value of employing a model to describe the data and understand the effects of independent variable manipulation was discussed.     

Conditioned response-contingent delays of the unconditioned stimulus in human aversive conditioning.

Four groups of subjects were given either 0. 100, 500, or 1,000 msec delays of the unconditioned stimulus (UCS) contingent upon the occurrence of a conditioned response (CR) and were given a UCS 515 msec after conditioned stimulus (CS) onset when a CR did not occur. A fifth group received standard classical conditioning trials with an interstimulus interval of 515 msec. Overall performance decreased as CR-contingent UCS delay increased, with the classical conditioning group approximating the performance of the group receiving the 100-msec delay. The data were analyzed with the two-phase model of conditioning and the following results were obtained: The duration of Phase 1 of the model increased with contingent delay; operator limits associated with CR trials or with combined CR-CR (CR absent) trials decreased as a function of delay; and operator limits associated exclusively with CR trials were unaffected by the delay. Subjects receiving a contingent delay of 0 msec gave the shortest latency responses and exhibited reliable latency decreases across trials, suggesting an attempt to "beat" the UCS. The results were interpreted as contrary to what would be expected from low-of-effect theories which postulate that reinforcement results from a CR-UCS interaction, although they could be subsumed under a drive or an associative strength theory in which the aversive, or CR-supportive, strength of the UCS is assumed to be negatively correlated with contingent UCS delay.     

Random controls: A rejoinder

Furedy, Poulos, and Schiffman (1975) have made a conclusion in direct contradiction to available data in skin conductance conditioning which show clearly that a stimulus designated to be random was, in fact, random with respect to an unconditioned stimulus. It was also pointed out that the overlap criterion does illustrate the weakness of the Toronto studies; that the random stimulus in the Prokasy, Williams, Kumpfer, and Lee (1973) paper was not excitatory; and that controlled studies for at least a decade have shown the first-interval response to be associative.