John Theios

One-way versus shuttle avoidance conditioning

Rats were trained to avoid shock with either a one-way procedure, a shuttle procedure, or both. One-way conditioning was found to be consistent with a two-step all-or-none process and was a much simpler task then shuttle conditioning which could not be accounted for by that process or by a linear operator process.

Single session conditioning of the nictitating membrane in the rabbit: Effect of intertriai interval

Abstract102 Ss were assigned to 3 groups and classically conditioned with a 45 sec., a 111 sec., or a 5 min. ITI. The CS was an 88 db buzzer, and the US was shock. For any given subject all conditioning trials took place within a single session. It was found that a U-shaped function described the relationship between trials to an acquisition criterion and ITI, with the 111 sec group performing better than either of the other groups.

Modification of the Rat's Saline Intake Gradient by Experience with Specific Concentrations

The amount of sodium chloride solution ingested by racs in an ad libiiu7n test sicuation at first increases with concentration, reaches a maximum with concentrations around ,995, and then decreases (Bare, 1949). In spite of emphasis on physiological explanations (Woodworth & Schlosberg, 1954, p. 662; Deutsch & Jones, 1960), it is quite possible that saline drinking behavior is in part determined by processes dependent upon prior experience, for example, learning (Bare, 1949). A learning explanation would become more plausible if it were demonstrated that the saline intake gradient could be modified by experience. The purpose of this experiment was to determine whether raising racs from birth on specific concentrations of saline as their only drinking fluid would alter the gradient of saline intake which is usually found with laboratory rats. METHOD

The mathematical structure of reversal learning in a shock-escape T-maze: Overtraining and successive reversals

Abstract Using escape from shock in a T-maze, overlearning and successive reversal learning experiments were conducted with rats. It was found that overtraining systematically retards reversal learning. With successive reversals, speed of reversal learning systematically increases and approaches a limit of one-trial learning. After 220 reversals, one-trial reversals occurred more than 80% of the time. The data were compared with quantitative predictions from a number of linear and Markov learning models. It was possible (a) to reject classes of models which were inadequate and (b) to relate changes in the values of parameters of the better models to amount of overtraining and number of reversals.

Theoretical interpretations of a Markov model for avoidance conditioning

Abstract Several alternative theoretical interpretations of a general Markov model for avoidance conditioning were considered. Experimental tests with two different conditioning procedures indicated that a two-stage conditioning interpretation (emotional conditioning followed by instrumental conditioning) was not tenable. Two interpretations are consistent with the obtained data. One is based on the notions of a temporary, imperfect memory and a relatively permanent, perfect memory for the association between the CS and an arousal response. The other involves representing the CS and the CS-plus-UCS as sets of stimuli with common components. It was possible to account for performance differences between rats permitted to make escape responses and rats prevented from making escape responses by differences in one parameter of the model and to demonstrate parameter invariance for the remaining parameters.

An incentive model for the overlearning reversal effect)

A theoretical model is proposed for the interaction of the effect of number of training trials and magnitude of reward on speed of reversal learning. The model was tested by an experiment involving 2 levels of reward magnitude and 4 degrees of training. An overlearning reversal effect was obtained under large reward but not with small reward. The data from the 8 groups of rats were well within chance limits of the quantitative predictions from the model.

Prediction of paired-associate latencies after the last error by an all-or-none learning model

An all-or-none learning model is presented which makes predictions for response latencies in paired-associate learning. The predicted latencies decrease on trials following the last error of a criterion run and accurately describe the latency data of an experiment by Peterson (1965).

A test of the competing response-interference hypothesis of extinction

Following training in a runway, two groups of rats were either confined in the goal box for 20 sec. during extinction trials or permitted to immediately jump out of the goal box. Contrary to the predictions of the interference theory, there were no differences between the groups in resistance to extinction. Within the jump group there was a moderate degree of covariation between jump frequency and resistance to extinction. However, this relationship can be explained by differences in general activity level rather than response interference.