Shaping avoidance behavior in restrained monkeys

Lever-pulling avoidance behavior of 24 monkeys was actively shaped with a manual shock-control box and a closed-circuit TV system. A negative reinforcement procedure was used wherein a periodically occurring body shock was postponed each time the subject moved toward the lever. All subjects were trainable with this method, two-thirds of them in fewer than five, 1- to 2-hr sessions. Negative reinforcement was more effective than a punishment procedure.     

Second-order optional avoidance as a function of fixed-ratio requirements

Two rhesus monkeys responded on a fixed-ratio schedule in Stimulus 1 (blue light) to avoid the onset of Stimulus 2 (green light). Failure to avoid Stimulus 2 required a second fixed-ratio performance to avoid Stimulus 3 (red light) in the presence of which unavoidable shock occurred. Relative frequencies of avoidance performance in the blue light and in the green light were inversely related to the ratio requirement under each stimulus condition. Both differential response-cost and avoidance-failure probability factors were related to the observed changes.     

Strategic behavior in monkeys

In a recent paper, Lee et al. examined adaptive decision-making processes by training monkeys to play a competitive game against a computer programmed to play using various strategies. They found that the monkeys' responses were sensitive to the computer's strategies and consistent with reinforcement learning. Research such as this strongly complements current research in behavioral economics. We propose some potential future directions for this work, and put forward conjectures about what might be learned about decision-making in humans.     

Signal functions in discriminated avoidance behavior

Four rats were trained to lever press under a discriminated avoidance/escape schedule in which separately signalled safe and warning periods were 100 sec and 32 sec respectively. The auditory and not the visual component of the compound warning signal became associated with the discriminative control of lever pressing. Avoidance behavior also came under temporal control, in that the probability of lever pressing increased as the warning period progressed. Timing began with the onset of the warning signal rather than the offset of the safe signal. However, after the warning signal had been progressively eliminated, timing began with the offset of the safe signal. When neither signal was normally available, the temporal distribution of avoidance behavior changed markedly. Drifts in the temporal distribution of lever pressing occurred throughout the study; these were manipulated for two animals.     

Extinction of Sidman avoidance behavior

Extinction of Sidman avoidance behavior by eliminating the noxious stimulus was studied in Sprague-Dawley rats with bar-pressing as the response. Each of three subjects was trained and extinguished on each of the following schedules in a different order: nondiscriminated, response-shock interval = 20 sec, shock-shock interval = 5 sec; nondiscriminated, response-shock interval = 40 sec, shock-shock interval = 5 sec; discriminated, response-white noise interval = 15 sec, noise-shock interval = 5 sec, shock-shock interval = 5 sec. Less than one 4-hr session was required for extinction for all procedures. When a warning stimulus was present, resistance to extinction increased. Subjects did not, however, respond to avoid the signal. Only small differences in extinction were found after training on different schedules with no warning signal.     

Stimulus control of avoidance behavior

The introduction of a warning signal preceding shocks greatly increased the effectiveness of avoidance responding. Periods of “warm-up” at the beginning of the session were eliminated, and the number of shocks received by the subjects was greatly reduced. With response-shock interval constant, response rate increased as the interval between the response and the onset of the warning signal was shortened. The response tended to occur shortly after the onset of the warning signal regardless of the duration of these “safe” periods. A greatly elevated response rate was maintained even when the duration of the safe period was reduced to 0.3 sec. Thus, the pre-shock signal obtained nearly exclusive control of the responding and overrode the usual “temporal discrimination” of the response-shock interval.     

Behavioral variability as avoidance behavior

This study aimed to investigate whether variable patterns of responses can be acquired and maintained by negative reinforcement under an avoidance contingency. Six male Wistar rats were exposed to sessions in which behavioral variability was reinforced according to a Lag contingency: Sequences of three responses on two levers had to differ from one, two or three previous sequences for shocks to be avoided (Lag 1, Lag 2 and Lag 3, respectively). Performance under the Lag conditions was compared with performance on a Yoke condition in which the animals received the same reinforcement frequency and distribution as in the Lag condition but behavioral variability was not required. The results showed that most of the subjects varied their sequences under the Lag contingencies, avoiding shocks with relatively high probability (≥ 0.7). Under the Yoke procedure, responding continued to occur with high probability, but the behavioral variability decreased. These results suggest that behavioral variability can be negatively reinforced.     

风险回避行为中的“红色图形效应”

以往研究发现,风险回避领域存在着一种经典的"图形效应"(即图形会比数字激发出个体更强的风险回避行为)。但以往研究通常只采用灰色或黑色来呈现风险信息。基于近来关于红色效应的探讨,本研究试图将颜色因素引入到图形效应中以探讨不同颜色下的图形效应特点。结果发现,相比于蓝色,红色能激发出个体更强的风险回避行为,且颜色对图形效应具有调节作用,即与蓝色相比,红色条件下出现了增强的图形效应,即"红色图形效应"。有关结果说明,红色作为一种危险警示颜色可以激发出个体更强的风险回避行为,且会诱发更大的图形效应。     

Generalization of free-operant avoidance behavior in pigeons

Three groups of four pigeons, trained to press a treadle on a free-operant avoidance schedule, were given auditory discrimination training. Alternating 2-min components of avoidance and no shock were paired with either a tone or white noise. The pigeons were subsequently given two types of generalization tests, with and without avoidable shocks scheduled. Two of the groups, trained interdimensionally, produced excitatory and inhibitory generalization gradients along the tone frequency dimension. A predicted post-discrimination gradient was computed from the algebraic summation of these gradients of excitation and inhibition. The predicted gradient was compared with the actual post-discrimination gradient obtained from the third group of pigeons that had been given intradimensional discrimination training on the tone frequency dimension. The predicted postdiscrimination gradient agreed in shape with the empirical postdiscrimination gradient. The results in general support Spence's (1937) gradient interaction theory.