Corvid Re-Caching without ‘Theory of Mind’: A Model

Abstract

Scrub jays are thought to use many tactics to protect their caches. For instance, they predominantly bury food far away from conspecifics, and if they must cache while being watched, they often re-cache their worms later, once they are in private. Two explanations have been offered for such observations, and they are intensely debated. First, the birds may reason about their competitors' mental states, with a ‘theory of mind’; alternatively, they may apply behavioral rules learned in daily life. Although this second hypothesis is cognitively simpler, it does seem to require a different, ad-hoc behavioral rule for every caching and re-caching pattern exhibited by the birds. Our new theory avoids this drawback by explaining a large variety of patterns as side-effects of stress and the resulting memory errors. Inspired by experimental data, we assume that re-caching is not motivated by a deliberate effort to safeguard specific caches from theft, but by a general desire to cache more. This desire is brought on by stress, which is determined by the presence and dominance of onlookers, and by unsuccessful recovery attempts. We study this theory in two experiments similar to those done with real birds with a kind of ‘virtual bird’, whose behavior depends on a set of basic assumptions about corvid cognition, and a well-established model of human memory. Our results show that the ‘virtual bird’ acts as the real birds did; its re-caching reflects whether it has been watched, how dominant its onlooker was, and how close to that onlooker it has cached. This happens even though it cannot attribute mental states, and it has only a single behavioral rule assumed to be previously learned. Thus, our simulations indicate that corvid re-caching can be explained without sophisticated social cognition. Given our specific predictions, our theory can easily be tested empirically.

An Exploration of the Social Brain Hypothesis in Insects

“…Calcium imaging (Joerges et al, 1997) and multi-electrode recording (Bender et al, 2010) techniques now enable investigations of activity patterns of neurons at the individual cell and circuitry levels, with the potential to assess the function of neural circuits in the learning and processing of social cues by individuals. Artificial neural networks are also extremely useful in developing crisp hypotheses and identifying circuitries that might enable various forms of social cognition, such a imitation (Laland and Bateson, 2001), face recognition (Aitkenhead and McDonald, 2003), or phenomena that might be interpreted as theory of mind (van der Vaart et al, 2012). For example, we lack clear predictions about how many changes in neural circuitry might be necessary to re-deploy a visual system evolved for identifying visual landmarks or prey for the purposes of face recognition.…”

Higher-order theory of mind in the Tacit Communication Game

“…at least second-order) theory of mind has been demonstrated both in tasks that require explicit reasoning using secondorder beliefs (Apperly, 2011;Perner & Wimmer, 1985) as well as in strategic games (Hedden & Zhang, 2002;Meijering, Van Rijn, Taatgen, & Verbrugge, 2011). However, the use of higher-order theory of mind appears to be a uniquely human ability; whether any non-human species is able to make use of theory of mind of any kind is under debate (Clayton, Dally, & Emery, 2007;Penn & Povinelli, 2007;Tomasello, 2009;Van der Vaart, Verbrugge, & Hemelrijk, 2012;Martin & Santos, 2014). This suggests that there may be specific settings in which the ability to reason about the unobservable mental states of others is evolutionarily advantageous.…”

Re-caching by Western Scrub-Jays (Aphelocoma californica) Cannot Be Attributed to Stress

“…A recent model of re-caching presents the possibility that scrub-jays might not be directly sensitive to prior observation, but to stress [7]. In a paper titled “ Corvid Re-Caching without Theory of Mind': a Model ”, the authors argue that the motivation to re-cache is indistinct from the drive to cache, and that caching is enhanced by stress.…”