Parallel working memory for spatial location and food-related object cues in foraging pigeons: binocular and lateralized monocular performance.

During foraging, animals can increase their success by both remembering feeding sites and remembering food-related object cues. Because earlier studies have tested either the site or object memory in isolation, the aim of the present study was to evaluate how efficiently birds can utilize both memories simultaneously. Furthermore, the idea was tested that lateralization might be the principle of brain organization that allows for efficient parallel processing. Pigeons learned to search for food in a complex maze with 16 baited sites. To obtain the maximum reward they had to perform two tasks in parallel, a spatial working memory task and an object-specific working memory task. Birds performed well on this dual task but, compared with spatial working memory alone, they were impaired during the first choices of a trial (Experiment 1). When the left and the right brain hemispheres were tested separately by means of monocular occlusion (Experiment 2), object discrimination was better when birds used their right eye/left hemisphere. This was most pronounced during the first choices of a trial. On the spatial component of the task, performance on binocular trials was better than on monocular trials, but monocularly both hemispheres performed at the same level. Results show that on this dual task, discrimination of food-related object cues predominantly involved the left brain hemisphere whereas both hemispheres contributed equally to spatial performance.