Varying temporal placement during CS of an added stimulus correlated with non-delivery of UCS

This experiment extends Pavlov’s method of contrasts for training a stimulus discrimination to the case of the cardiac conditional response in the rhesus monkey. It explores the parameter of temporal placement of an additional stimulus (“CS₂”) within a 10-sec CS (or “CS₁”), with the appearance of the former stimulus on any trial signalling the absence of UCS (electric shock) on that trial. This experimental paradigm is a parallel to that of the “intruded stimulus” studies in operant conditioning. In both cases, several ways of describing the function of the added stimulus are possible, but all seem reducible to the same operational terms. Data were taken in the present study with respect to the form and latency of the cardiac rate changes produced by intrusion of CS₂ (light), across a range of placements varying from simultaneity with CS₁ (a different light) onset to two sec before UCS would have been delivered. The control of CS₂ over the cardiac rate CR was occasionally exhibited with a latency as short as three beats after stimulus onset. The order of CS₂ temporal placements to which a subject was exposed was a factor in determining the form of the conditioned cardiac rate response to CS₁.     

The use of an untrained index response in a conditioned suppression paradigm

The need for extended training and motivational manipulations when using an instrumental index response in a conditioned suppression paradigm is often problematic. An index response requiring no prior training and no manipulation of motivational states is described. An experiment which exemplifies the use of this index response in a conditioned suppression paradigm is reported.     

On-line brain stimulation: Measurement of threshold of reinforcement

This program and interface for a small computer (PDP8/e) performs the following operations: generates and delivers constant current stimulation to the brain of an animal, monitors electrical resistance at the stimulating electrode, and calculates the threshold of reinforcement based upon the frequency of characteristic pauses in the animal’s responding.     

The time it takes to make veridical size and distance judgments

Two experiments measuring the time it takes to make veridical size judgments under normal (unreduced) conditions of viewing showed that RT tended to increase with increases in viewing distance between 122 and 305 cm, even for targets subtending the same visual angle at all distances. Two experiments measuring the time it takes to judge distance under the same conditions did not reveal any difference in RT as a function of the extent-of-distance judged. Established accounts of size perception do not suggest an explanation of these findings.     

Temporal summation at the warmth threshold

Threshold levels for warmth aroused by infrared irradiation were measured in sLx Ss at durations between 0.05 and 10 sec. Beyond a critical duration of about a second, the threshold does not depend on duration. Below critical duration time t trades for irradiance ? by the formula ? = kt^?0.82. That these properties do not depend much on areal extent of stimulation was demonstrated by a study that compared temporal summation for two different areas of the same S’s skin. Individual differences in apparent absolute sensitivity were explored under the rubric of the theory of signal detection.     

Reaction time as a measure of summation of warmth

Reaction time (RT) to radiant heat applied to the forehead and to the back was found to decrease monotonically as a function of two variables: intensity (flux density) and areal extent of stimulation. Intensity and area can thus be traded one for the other to preserve a constant RT. It has previously been shown that intensity and area can be traded to preserve a constant degree of apparent warmth, as determined by magnitude estimation. RT and magnitude estimation therefore agree in showing that the warmth sense displays spatial summation, and both show that summation is very great. They also agree in showing that the foreheadés sensitivity greatly exceeds the backés, and the exact trading rules revealed by magnitude estimation and RT agree well at low and moderate intensities.