Concurrent avoidance of shocks by pigeons pecking a key

Three pigeons were studied on concurrent, unsignaled, avoidance schedules in a two-key procedure. Shock-shock intervals were two seconds in both schedules. The response-shock interval on one key was always 22 seconds, while the response-shock interval associated with the other key was varied from 7 to 52 seconds in different experimental conditions. Response rates on the key associated with the varied schedule tended to decrease when the response-shock interval length was increased. Responding on the key associated with the constant schedule was not systematically affected.     

Timing the second response in two-response avoidance.

Rats were trained on a free-operant avoidance task requiring two lever presses within R seconds, with the opportunity for each response distinguished by differing stimuli. Response latencies at a variety of response-shock intervals were found to be proportional to the time available for the response. These results are shown to be consonant with a scalar expectancy model of timing behavior.     

Duration-reduction of avoidance sessions as negative reinforcement

Five rats were exposed to a shock-postponement procedure in which responses on each of two levers initially had equivalent effects. After an initial training sequence that ensured at least some responding on each lever, an additional consequence was made conjointly operative on the previously less-preferred lever for each animal. Each response on this lever continued to postpone shock, but also reduced the session duration by one minute. The conjoint contingencies were operative until, through session-shortening responses and the passage of time, the session was scheduled to end in two minutes; during the final two minutes the session-shortening contingency was disabled while the shock-postponement contingency continued to be operative on both levers. When responding shifted to a predominance on the session-shortening lever, the conjoint contingency was shifted to the other lever; for four of the five rats this reversal was followed by two additional reversals. Two of the rats' responding showed clear, strong, and unambiguous sensitivity to the session-shortening contingency. The responding of two others was also systematically controlled by that contingency, but the effects were less clearcut. The fifth animal showed an initial shift when session-shortening was introduced, but its subsequent behavior proved insensitive to reversals of procedure. The results clearly indicate a sensitivity of behavior to events on a time scale quite distinct from that of immediate consequences. They also support an interpretation of avoidance sessions, considered in their entirety, as events whose contingent relationship to behavior can affect that behavior—even in the absence of stimuli that delineate those relationships. Finally, these results support an interpretation of aversively based conditioning within a broader context, analogous to the “open versus closed economy” interpretation of appetitively controlled behavior.     

Performance of humans in concurrent avoidance/positive-reinforcement schedules

Performance maintained under concurrent schedules consisting of a variable-interval avoidance component and a variable-interval positive-reinforcement component was studied in three human subjects using points exchangeable for money as the reinforcer. The rate of responding in the avoidance component increased, and the rate of responding in the positive-reinforcement component declined, as a function of the frequency of point-losses avoided in the avoidance component. The performance of all three subjects conformed to equations proposed by Herrnstein to describe behavior in concurrent schedules. The logarithms of the ratios of the response rates in the two components, and the logarithms of the ratios of the times spent in the two components, were linearly related to the logarithms of the ratios of the frequency of loss avoidance in the avoidance component to the frequency of reinforcement in the positive-reinforcement component. When a changeover delay of 5.0 sec was imposed, the slopes of the linear functions were close to 1.0 in the case of two subjects, whereas the third subject exhibited significant undermatching. For two subjects the changeover delay was then reduced to 2.0 sec; in both cases the slopes of the linear functions were lower than under the 5.0-sec condition. One subject participated in a third phase, in which no changeover delay was imposed; there was a further reduction in the slopes of the linear functions.     

Signalled free-operant avoidance of shock by pigeons pecking a key

Two pigeons were trained to peck a key under a free-operant avoidance schedule. Then, changes in key color signalled the beginning (safe period) and the end (warning period) of the response-shock interval, with a response required to change the key color. Finally, a change in key color signalled the warning period and either a response or a shock reinstated the safe stimulus. During signalled avoidance, response rate was higher during the warning stimulus than during the safe stimulus. More responding tended to occur in the warning stimulus when it was terminated by either a response or a shock than by only a response. In either procedure, response latency during the warning stimulus was a function of the duration of the warning stimulus. In general, response and shock rate were higher during unsignalled than during signalled avoidance. When the warning stimulus was brief, the results were similar to those of unsignalled avoidance. These results confirm previous findings with pigeons, are in general agreement with data provided by other species in studies of signalled avoidance, and thereby indicate the transituationality of the key-pecking operant.     

Clock control of human performance on avoidance and fixed-interval schedules

The avoidance and fixed-interval performances of human subjects were studied in two experiments. Addition of time-correlated stimuli (added clock) improved behavioral efficiency, since response rates decreased without decreases in reinforcement rates. Response-dependent display of the clock maintained a second, observing response and reductions in clock duration weakened such observing behavior. Generally, the reinforcing properties of the clock were more apparent with the avoidance than with the fixed-interval schedule, a finding attributed to temporal cues already provided by delivery of the fixed-interval reinforcers. Reduced rates of the main response when the clock was dependent on an observing response were more than offset by rates of the observing response in the majority of subjects. Thus, the results do not support an interpretation of the reinforcing properties of added clocks simply in terms of work reduction.     

Human social defeat and approach–avoidance: Escalating social-evaluative threat and threat of aggression increases social avoidance

Basic research on avoidance by Murray Sidman laid the foundation for advances in the classification, conceptualization and treatment of avoidance in psychological disorders. Contemporary avoidance research is explicitly translational and increasingly focused on how competing appetitive and aversive contingencies influence avoidance. In this laboratory investigation, we examined the effects of escalating social-evaluative threat and threat of social aggression on avoidance of social interactions. During social-defeat learning, 38 adults learned to associate 9 virtual peers with an increasing probability of receiving negative evaluations. Additionally, 1 virtual peer was associated with positive evaluations. Next, in an approach–avoidance task with social-evaluative threat, 1 peer associated with negative evaluations was presented alongside the peer associated with positive evaluations. Approaching peers produced a positive or a probabilistic negative evaluation, while avoiding peers prevented a negative evaluation (and forfeited a positive evaluation). In an approach–avoidance task with social aggression, virtual peers gave and took money away from participants. Escalating social-evaluative threat and aggression increased avoidance, ratings of feeling threatened and threat expectancy and decreased ratings of peer favorableness. These findings underscore the potential of coupling social defeat and approach–avoidance paradigms for translational research on the neurobehavioral mechanisms of social approach–avoidance decision-making and anxiety.     

冲突水平的变化诱发冲突适应

冲突适应是重要的认知控制现象, 反映了认知控制的动态过程。然而, 目前为止对于冲突水平上的差异能否诱发冲突适应尚不清楚。本研究采用字母Flanker的变式, 通过改变目标-分心物的一致性操纵冲突水平, 探究冲突水平的变化对认知控制调整的影响。结果发现被试的反应时间随冲突水平的提高而增加; 而且先前试次的一致性影响当前试次的干扰效应, 无冲突和低冲突、无冲突和高冲突、低冲突和高冲突条件之间均出现了典型的冲突适应。本研究结果表明, 除了冲突的有无, 冲突水平的变化也能诱发冲突适应, 支持更大的冲突驱动更强的认知控制, 而且冲突诱发的认知控制的功能可能通过注意聚焦实现。这一发现为冲突监测理论的注意调节机制提供了直接的支持证据, 对于促进冲突适应的相关研究具有重要意义。     

概念内隐记忆中的注意促进效应

Swallow和Jiang (2010)最早发现, 编码时的目标探测会促进同时呈现的背景信息在随后记忆测验中的表现, 并将这一现象称为注意促进效应(Attentional Boost Effect, ABE)。随后研究发现这一现象并不会出现在概念内隐测验中, 由此提出目标探测主要促进的是背景信息的知觉加工, 而非语义加工。本研究通过3个实验, 操纵了对背景信息的编码加工类型(知觉加工或概念加工)。结果发现, 当与目标探测同时进行的是对背景信息的概念加工任务, 则ABE会出现在随后的概念内隐测验中。反之, 当对背景信息进行的是知觉加工任务时, 则ABE会出现在随后的知觉内隐测验而不是概念内隐测验中。这些结果表明, 目标探测既可能促进背景信息的知觉加工, 也可能促进背景信息的语义加工, 但只有在目标探测下背景信息的编码加工与随后内隐测验中所依赖的提取加工具有一致性, 才会产生ABE。     

Horizontal eye movements foster approach to negative pictures but do not change emotional valence: A dopaminergic regulation hypothesis

A new dopaminergic regulation hypothesis is proposed based on two experiments exploring eye-movement effects. In the Eye Movement Desensitization and Reprocessing (EMDR) and Saccade-Induced Retrieval Enhancement (SIRE) domains, eye-movement mechanisms are mainly studied with explicit measures. Here implicit and explicit measures of emotion and memory for positive and negative pictures were investigated after eye movements or fixation in extreme right-handers. Eye movements enhanced explicit recognition predominantly for negative pictures. The absence of implicit repetition priming in both experiments supported a dissociation between implicit and explicit memory. Motivational eye-movement effects emerged but implicit and explicit affect remained unchanged. Experiment 2 revealed, after initial freezing to negative pictures, an acceleration, particularly of approach responses. Eye movements are postulated to foster approach towards negative memories, and promote, though dopaminergic pathways from the Superior Colliculus, enhanced explicit memory and active emotion regulation, primarily in persons with a collateralization of eye and dopamine dominance.