Adapting to the environment requires using feedback about previous decisions to make better future decisions. Sometimes, however, the past is not informative and taking it into consideration leads to worse decisions. In psychophysical experiments, for instance, humans use past feedback when they should ignore it and thus make worse decisions. Those choice history biases persist even in disadvantageous contexts. To test this persistence, we adjusted trial sequence statistics. Subjects adapted strongly when the statistics confirmed their biases, but much less in the opposite direction; existing biases could not be eradicated. Thus, even in our simplest sensory decisions, we exhibit a form of confirmation bias in which existing choice history strategies are easier to reinforce than to relinquish.Abstract
When making choices under conditions of perceptual uncertainty, past experience can play a vital role. However, it can also lead to biases that worsen decisions. Consistent with previous observations, we found that human choices are influenced by the success or failure of past choices even in a standard two-alternative detection task, where choice history is irrelevant. The typical bias was one that made the subject switch choices after a failure. These choice history biases led to poorer performance and were similar for observers in different countries. They were well captured by a simple logistic regression model that had been previously applied to describe psychophysical performance in mice. Such irrational biases seem at odds with the principles of reinforcement learning, which would predict exquisite adaptability to choice history. We therefore asked whether subjects could adapt their irrational biases following changes in trial order statistics. Adaptability was strong in the direction that confirmed a subject’s default biases, but weaker in the opposite direction, so that existing biases could not be eradicated. We conclude that humans can adapt choice history biases, but cannot easily overcome existing biases even if irrational in the current context: adaptation is more sensitive to confirmatory than contradictory statistics.