A team of researchers from the University of Warwick and Indiana University has found that humans move between patches in their memory using the same strategy as birds searching among bushes for berries or bees flitting between flowers for pollen.
Marsh Wren foraging in the reeds (Alan Vernon)
The results, published in the Psychological Review, reveal parallels between animals looking for food in the wild and humans searching for items within their memory – suggesting that people with the best memory foraging strategies are better at recalling items.
The researchers asked participants to recover from memory as many animal names as they could in 3 min and then compared the results with a classic model of optimal foraging in the real world – the marginal value theorem – which predicts how long animals will stay in one patch before jumping to another.
“A bird’s food tends to be clumped together in a specific patch – for example on a bush laden with berries,” said Dr. Thomas Hills, an associate professor at the University of Warwick. “But when the berries on a bush are depleted to the point where the bird’s energy is best focused on another more fruitful bush, it will move on. This kind of behavior is predicted by the marginal value theorem, for a wide variety of animals.”
The responses of 141 undergraduates (46 men and 95 women) from Indiana University were then analyzed by the team using a categorization scheme and also a semantic space model, called BEAGLE.
This model identifies clusters in the memory landscape based on the way words are related to one another in natural language.
“Because of the way human attention has evolved, we wondered if humans might use the same strategies to forage in memory. It turns out, they do,” Dr. Hills explained. “When faced with a memory task, we focus on specific clusters of information and jump between them like a bird between bushes.”
“For example, when hunting for animals in memory, most people start with a patch of household pets – like dog, cat and hamster.”
“But then as this patch becomes depleted, they look elsewhere. They might then alight on another semantically distinct ‘patch’, for example predatory animals such as lion, tiger and jaguar.”
The results show that people who either stay too long or not long enough in one ‘patch’ did not recall as many animals as those who better judged the best time to switch between patches. In other words, people who most closely adhered to the marginal value theorem produced more items.
