Anyone who has spent time in London sees the merits of carrying an umbrella, despite the inconvenience, and the sky currently being blue. This type of planning, which is based on expectations and sometimes requires one to forgo immediate wants and comforts, has historically been thought to be unique to humans and great apes.
Previous research has shown that corvids can plan for, among other things, the next day’s breakfast by stashing food in different compartments; however, this behavior is considered to be different from the planning exhibited by apes. As most corvids habitually hide food, their admittedly impressive behavior might reflect a specific adaptation confined to the food hoarding domain. The new study, published in the journal Science, now reveals that ravens are at least as good as apes at general planning tasks as well.
The authors of the study, Can Kabadayi and Mathias Osvath, let ravens solve tasks that they don’t encounter in the wild, and hence lack specific adaptations for: tool use, and bartering with humans. Another strength in choosing these tasks is that they have been tested on apes, so this creates opportunities for direct comparisons between the species, says PhD student Can Kabadayi.
Over several experiments, the ravens could select either a tool or a token from among a set of objects to solve a future problem in another location. The tool allowed the birds to retrieve a reward from a box, and the token could be given to a human in exchange for a reward. The delay between the item selection and the task ranged from 15 minutes to 17 hours depending on the experiment. The ravens planned for bartering more accurately than apes, and they were on par with them in the tool-using tasks, despite that they lack predispositions for tool handling.
The study also tested the ravens’ self-control by including a small piece of food among the objects they could choose from, including the tools and tokens, and then varying the amount of time between the choice and the task.
“It is a well-known psychological mechanism in humans that time devalues reward; the longer we have to wait, the less it will be worth”, explains Mathias Osvath, Associate Professor in Cognitive Zoology at Lund University.
In other words, the ravens should exert self-control by selecting the tool or token more often when they believe the opportunity to use it will be closer in time. This is exactly what they did, suggesting that ravens took the time delay into consideration when choosing. Overall their level of self-control is similar to that of the great apes.
“To be able to solve tasks like these, one needs a collection of cognitive abilities working in concert, such as inhibitory skills and different forms of memory. That ravens show similar functions, and combine them in ways similar to apes, despite a last common ancestor as far back as 320 million years ago, suggests that evolution likes to re-run good productions”, concludes Mathias Osvath.
Publication: Ravens parallel great apes in flexible planning for tool-use and bartering (at Science online)
mathias [dot] osvath [at] lucs [dot] lu [dot] se ()