Conflict Test Battery for Studying the Act of Facing Threats in Pursuit of Rewards

Survival depends on the ability of animals to avoid threats and approach rewards. Traditionally, these two opposing motivational systems have been studied separately. In nature, however, they regularly compete for the control of behavior. When threat- and reward-eliciting stimuli (learned or unlearned) occur simultaneously, a motivational conflict emerges that challenges individuals to weigh available options and execute a single behavioral response (avoid or approach). Most previous animal models using approach/avoidance conflicts have often focused on the ability to avoid threats by forgoing or delaying the opportunity to obtain rewards. In contrast, behavioral tasks designed to capitalize on the ability to actively choose to execute approach behaviors despite threats are scarce. Thus, we developed a behavioral test battery composed of three conflict tasks to directly study rats confronting threats to obtain rewards guided by innate and conditioned cues. One conflict task involves crossing a potentially electrified grid to obtain food on the opposite end of a straight alley, the second task is based on the step-down threat avoidance paradigm, and the third one is a modified version of the open field test. We used diazepam to pharmacologically validate conflict behaviors in our tasks. We found that, regardless of whether competing stimuli were conditioned or innate, a low diazepam dose decreased risk assessment and facilitated taking action to obtain rewards in the face of threats during conflict, without affecting choice behavior when there was no conflict involved. Using this pharmacologically validated test battery of ethologically designed innate/learned conflict tasks could help understand the fundamental brain mechanisms underlying the ability to confront threats to achieve goals.

Conflict-mediated tasks for studying the act of facing threats in pursuit of rewards

Survival depends on the ability of animals to avoid threats and approach rewards. Traditionally, these two opposing motivational systems have been studied separately. In nature, however, they regularly occur simultaneously. When threat- and reward-eliciting stimuli (learned or unlearned) co-occur, a motivational conflict emerges that challenges individuals to weigh available options and execute a single behavioral response (avoid or approach). Previous animal models using approach-avoidance conflicts have often focused on the ability to avoid threats by forgoing the opportunity to obtain rewards. In contrast, behavioral tasks designed to capitalize on the ability to actively choose to execute approach behaviors despite threats are lacking. Thus, we developed three conflict-mediated tasks to directly study rats confronting threats to obtain rewards guided by innate and conditioned cues. One conflict task involves crossing a potentially electrified grid to obtain food on the opposite end of a straight alley, the second task is based on the step-down threat avoidance paradigm, and the third one is a modified version of the open field test. We used diazepam to pharmacologically validate conflict-mediated behaviors in our tasks. We found that, regardless of whether competing stimuli were conditioned or innate, a low diazepam dose facilitated taking action to obtain rewards in the face of threats during conflict, without affecting choice behavior when there was no conflict involved. Using this validated set of innate/learned conflict-mediated tasks could help understand the underlying brain mechanisms that allow animals to confront threats, by actively suppressing defensive responses, to achieve goals.

Use of cognitive bias as a welfare tool in poultry

In human psychology, the link between cognition and emotions is broadly accepted. However, the idea of using the interaction between cognition and emotions as a tool for a better understanding of animal emotions or for welfare assessment is relatively new. The first avian species used in cognitive bias tests was the European starling followed by the domestic chicken and other species. The most frequently used paradigm is the affect-induced judgment bias. There are many variations of the judgment bias tests in birds. The test itself is preceded by discrimination training. Discrimination tasks vary from visual cue discrimination, discrimination of time intervals to spatial location discrimination. During the discrimination training, birds flip or do not flip the lids of the food dishes, and their latency to approach the cues in a straight alley maze, in a two-choice arena, or different locations in spatial judgment task arena are measured. Alternately, the birds fulfill operant tasks in a Skinner box. Before or after the discrimination training phase, birds are subjected to manipulations that are hypothesized to induce positive or negative emotional states. In the last stage, birds are subjected to judgment bias tests. The assumption is that animals in a negative affective state would more likely respond to ambiguous cues, as if they predict the negative event, than animals in a more positive state. However, the results of some avian studies are inconsistent, particularly those studying the effect of environmental enrichment. In starlings, each of the three studies has supplied conflicting results. In poultry, none of the four studies demonstrated a positive effect of environmental enrichment on emotional states. Only the study using unpredictable stressors in combination with environmental complexity showed that animals kept in a more complex environment are more optimistic. Manipulation of the social environment seems to be more effective in judgment bias induction. Conflicting results could be attributable to the design of the tests, the manner of affect induction, or the data analysis. Further optimization and validation of avian cognitive bias tests could help to avoid problems such as the loss of ambiguity. New methods of attention and memory bias testing are promising. However, regardless of the abovementioned complications, a cognitive bias paradigm is a valuable tool, which can help us better understand avian emotions and assess poultry welfare.

Perseveration of the Partial Reinforcement Effect in Extinction with Rats over Two Phases of Extinction and Two Stages of Continuous Reinforcement

One group of 10 male albino rats was given partial reinforcement while the other 10 rats received continuous reinforcement in a straight alley. Subjects then experienced five consecutive stages of Extinction 1, Continuous Reinforcement 1, Extinction 2, Continuous Reinforcement 2, and finally, Extinction 3. Analysis showed the partial reinforcement effect in extinction was sustained over two stages of extinction and two stages of continuous reinforcement, since subjects receiving partial reinforcement ran faster than rats given continuous reinforcement throughout all three of the extinction periods. The results seem to support those of Amsel's (1967) and Capaldi's (1967) theoretical formulations of the partial reinforcement effect in extinction.

Effects of Preshift Small Magnitude of Reward Received during Goalbox Placements on the Negative Contrast Effect

During preshift, one experimental group of rats was given a large magnitude of food reward following a traversal of a straight alley and during a goalbox placement, while the other experimental group was given a small reward during goalbox placement and a large reward following a run. During postshift, all experimental groups were given a small reward of food following a traversal down the runway and during a goalbox placement. A control group was maintained on small reward during placements and following a traversal throughout the study. Only the group who received preshift large reward during placement and following a runway response ran slower to small reward during postshift than the control group maintained on small reward (negative contrast effect).

Effects of Delay of Reinforcement with Reduction of Confinement in the Goal-Box and Elimination of Handling Immediately following Runway Traversal

24 male rats were randomly assigned into one of three groups. The first group was immediately reinforced with food pellets upon entering a wide goal-box area after running down a straight alley. The second group was reinforced with food pellets 10 sec. after they placed their noses above the goal cup. A third group was reinforced 30 sec. after they placed their noses above the goal cup. All animals were given a total of 72 trials (four trials per day). The results indicated that rats given immediate reinforcement ran faster than those with a 10-sec. delay which were faster than those with a 30-sec. delay. These findings suggest that the results of the previous studies were due to delay of reinforcement effects and not confinement in the goal-box or handling following a run.

Effects of Testosterone Propionate upon Habit-Reversals and One-Trial Learning by Castrated White Rats

32 male white rats, littermates from mothers of same strain, started to learn 20 habit-reversal problems at 50 days of age in an E-maze for water by the noncorrectional method. They were divided into 3 groups. Two groups of 11 each had been castrated at 32 days of age, and a group of 10 served as control. One castrated group received daily injections of testosterone propionate at 1 mg per kg of body weight 11 days after surgery. The other castrated group and the normal controls received saline. A week of preliminary training accustomed the animals to the daily routine of injection, about 30 min. before being put in the drinking box of a straight alley which they ran for water during the last 2 days. In maze learning proper, after a rat made 9 correct choices on 10 daily trials, the goal was reversed for the next problem. Early in learning, there were some fluctuations in performance, but throughout the rest of the experiment, the castrated-saline group was consistently and significantly inferior to the normals, testifying to the detrimental effect of castration upon adaptive ability in learning successive reversal problems. The fact that the castrated-testosterone group was far superior to the castrated-saline group and exhibited no significant difference from the normal-saline group shows unequivocally that testosterone propionate has a therapeutic property of raising the learning ability of the retarded, castrated white rats to a normal level. A theory is suggested.