Cognitive control of memory in a food-storing and a non-storing bird species.

Scatter hoarding black-capped chickadees use memory to relocate hidden food, often after delays of hours or days. The ability of these birds to maintain accurate memories of the location and current status of many food caches while engaging in other distracting daily activities suggests that their memory may be especially resistant to competing cognitive load. We measured resistance to competing cognitive load during spatial memory tests in black-capped chickadees (Poecile atricapillus) and a non-caching species, dark-eyed juncos (Junco hyemalis). Birds were presented with two types of task. In the Discrimination task, birds learned by trial-and-error to select a target from among 2 distractors. In the Match-to-Sample task, birds viewed a sample which they had to remember in order to correctly select it from among two distractors at test. On two-thirds of trials, the tasks were presented Stand-Alone: after birds initiated a trial, they completed either a Discrimination or a Match-to-Sample task. The remaining trials were Concurrent causing a competing cognitive load: after birds intiated a trial, they saw the sample for the Match-to-Sample task, then completed a Discrimination during the retention interval, and finally completed a Match-to-Sample test. Competing cognitive load reduced accuracy of juncos significantly more than accuracy of chickadees. The need to encode and retain the locations of multiple food caches may have led to the evolution of enhanced cognitive control of memory in black-capped chickadees.