Decision making under risk: framing effects in pigeon risk preferences.

When humans face probabilistic outcomes, their choices often depend on whether the choice is framed in terms of losses or gains. In the present research, we gave pigeons a choice between risky (variable) outcomes and safe (constant) outcomes that resulted in the same net reward. In Experiment 1, in which the outcomes represented a loss, the pigeons preferred the risky alternative. In Experiment 2, in which the outcomes represented a gain, the pigeons were indifferent between the two alternatives. In Experiment 3, in which the outcomes represented neither a gain nor a loss, the pigeons strongly preferred the risky alternative. The results were interpreted in terms of the relative value of gains and losses given to the alternatives by pigeons in the context of a risky and safe choice. In Experiment 4 we tested that hypothesis by giving pigeons a choice between a risky and safe alternative with the same net outcome, in the context of a gain associated with the safe alternative, but no gain or loss associated with the risky alternative. In support of the interpretation of the first three experiments, with the safe alternative associated with a gain, the pigeons now preferred the safe alternative. These results were discussed in terms of economic and foraging theories and were contrasted with the aversion to uncertainty (risk) more typically shown by humans.

Pigeons are attracted to a perceived gain without an actual gain.

Reference dependence refers to the reduced value of a reward that is less than expected, or the added value of a reward that is greater than expected. There is evidence that when pigeons are offered an alternative that has 1 pellet versus an alternative that has 2 pellets, but one of the two pellets offered will be removed, the pigeons prefer the originally presented 1 pellet (loss aversion). In the present research, we tested for the opposite effect (gain attraction). In Experiments 1 and 2, pigeons could choose between 2 pellets, each one on a distinctive background. If they chose the optimal alternative, they received a second pellet. In Experiment 2, the second pellet obtained was the one not initially chosen (a task sometimes referred to as the ephemeral reward task). Pigeons learned to choose optimally in both experiments. In Experiment 3, we tested the pigeons for reference dependence. Pigeons were given an alternative that offered them one pellet or two pellets, if they chose the one-pellet alternative, they received an additional pellet, and if they chose the two-pellet alternative, they received the two pellets. In keeping with the reference dependence hypothesis, the pigeons preferred the 1-pellet alternative that gave them an extra pellet. These effects are related to similar findings with humans, including the endowment effect.

Visual alternation by pigeons: Learning to select or learning to avoid.

In the visual alternation task, pigeons learn to alternate between two stimuli (e.g., red and green) that vary randomly in location from trial to trial. The task is inherently difficult because animals tend to return to a stimulus to which they have just received reinforcement for responding. Williams (1971, Journal of the Experimental Analysis of Behavior, 15, 129-140) suggested that pigeons learn this task by learning to avoid the stimulus most recently chosen. The present experiment tested this hypothesis by involving three groups. The Standard Group replicated Williams' design. For the New Correct Group, following a correct (reinforced) response, on the next trial, the color of the new correct stimulus changed. For example, if it had been green, it changed to either blue or yellow, but the color of the new incorrect stimulus (the one that was just correct) remained the same (i.e., red). For the New Incorrect Group, following a correct response, on the next trial, the color of the new incorrect stimulus changed. For example, if it had been red, it changed to blue or yellow, but the color of the new correct stimulus remained (i.e., green). The Standard Group replicated Williams's finding that pigeons can learn the alternation task. Consistent with Williams's hypothesis, pigeons in the New Correct Group showed evidence of learning the alternation task, whereas pigeons in the New Incorrect Group showed little evidence of learning. Acquisition of the visual alternation task suggests that pigeons are cognitively flexible enough to overcome their natural tendency to repeat their most recently reinforced response to a stimulus.