Memory and the value of social information in foraging bumble bees.

Not all information should be learned and remembered. The value of information is tied to the reliability and certainty of that information, which itself is determined by rates of environmental change, both within and across lifetimes. Theory of adaptive forgetting and remembering posits that memory should reflect the environment, with more valuable information remembered for longer amounts of time. Theory on biological preparedness predicts that rates of reliability through evolutionary time should influence what is learned and remembered. We use these ideas to predict that differential memory use will reflect the underlying value of the information being learned. We test this by comparing the learning and memory of social information versus floral information in foraging bumble bees. Bumble bees are extremely flexible in their use of both types of information and evidence suggests that social information is "special," reflecting biological preparedness. Our experiment tests how bumble bees learn and remember social and floral information when their reliabilities, and thus value, differ. We find that bees learn both types of information at a similar speed. Bees show a decrement of memory of the trained associations in both treatments, but retain trained socially reliable information for longer, at both 4-hour and 8-hour retention intervals. Both training treatments influence whether bees match or avoid the locations of demonstrators, and this interacts with retention interval. Bees trained under reliable floral cues and unreliable social cues avoid conspecifics after 8-hr and 24-hr retention intervals. Bees thus learn about the reliability or unreliability of social cues and use this to modify their choices across time.