A paper in today’s issue of Nature shows that Western scrub-jays (Aphelocoma californica) are capable of planning for the future, a cognitive skill that was previously believed to be limited to humans. The work, by researchers at Cambridge University’s Department of Experimental Psychology, builds on previous studies which show that scrub-jays are capable of storing up to 100,000 nuts in 30,000 different caches, and retrieving the stored food up to 9 months later. If they notice another bird observing their caching, the scrub-jays later return to the caches and hide the food elsewhere.
These tasks suggest that scrub-jays are capable of anticipating future needs and planning for them, and it is this ability that Raby et al investigated in the current study. In the experiments, scrub-jays were kept in large cages containing three compartments, and presented with different kinds of food in different locations, according to a strict feeding schedule, such that they learnt where food would be available for them the next morning.
During their training, the birds were confined to one of the side compartments in the mornings, after not eating during the night. In the ‘breakfast’ room, they were given powdered pine nuts, which they could not store, whereas in the ‘no breakfast’ room they were given no food. Over a period of 8 days, the birds’ confinement alternated between these two rooms. After training, they were unexpectedly presented, in the evening, with whole instead of powdered pine nuts in the central room. It was found that the birds collected the nuts and stored them in sand-filled trays in the side compartments. The jays cached the nuts in the ‘no breakfast’ room far more frequently than in the ‘breakfast’ room, in anticipation of being confined there without food the next morning.
These results could be explained by a conditioned response which leads the birds to store food in locations previously associated with hunger, so a second experiment was designed to rule out this possibility. The birds were taught to expect breakfast in both side rooms. In one of the rooms, they were always given peanuts, and in the other, dog kibble. In this set up, the scrub-jays cached peanuts in the room where they were presented with dog kibble, and vice versa, so that they would have a choice of foods when placed in either compartment the following morning. Again, this experiment provides evidence of forward planning by the jays.
In 1983, Endel Tulving argued that animals “cannot travel back in the past in their own minds”; in other words, animals do not have an episodic (autobiographical) memory. Similarly, the Bischof-Köhler hypothesis states that only humans are capable of removing themselves from current motivations and planning for future needs. More recently, Suddendorf and Corballis suggested that animals are incapable of “mental time travel” – they live only in the present and are incapable of recalling past events or anticipating future ones.
These new findings provide strong evidence for prospective cognition in scrub-jays, and challenge the assertion that only humans have the ability to think ahead. The ability to store food in tens of thousands of caches shows that jays remember, and recall, information about what food they have stored, as well as where and when they stored it; this ability seems to be very similar to human episodic memory. Recent research shows that episodic memory is necessary for anticipating the future: people with hippocampal damage are not only unable to recall past events, but also cannot envisage themselves participating in future events. It is known that hippocampal damage impairs the navigational abilities of homing pigeons, and it would be interesting to see if hippocampal damage also affects the ability of scrub-jays to plan for the future.
Raby, C. R., et al. (2007). Planning for the future by western scrub-jays. Nature 445: 919-921. [Abstract]
Suddendorf, T. & Busby, J. (2003). Mental time travel in animals? Trends Cog. Sci. 7: 391-396. [Full text]