On the lack of evidence that non-human animals possess anything remotely resembling a ‘theory of mind’

Abstract

After decades of effort by some of our brightest human and non-human minds, there is still little consensus on whether or not non-human animals understand anything about the unobservable mental states of other animals or even what it would mean for a non-verbal animal to understand the concept of a 'mental state'. In the present paper, we confront four related and contentious questions head-on: (i) What exactly would it mean for a non-verbal organism to have an 'understanding' or a 'representation' of another animal's mental state? (ii) What should (and should not) count as compelling empirical evidence that a non-verbal cognitive agent has a system for understanding or forming representations about mental states in a functionally adaptive manner? (iii) Why have the kind of experimental protocols that are currently in vogue failed to produce compelling evidence that non-human animals possess anything even remotely resembling a theory of mind? (iv) What kind of experiments could, at least in principle, provide compelling evidence for such a system in a non-verbal organism?

Empirical approaches to the study of language evolution

“…A long-standing tradition held that Btheory of mind^(ToM) is uniquely human (Penn & Povinelli, 2007;Povinelli et al, 1990;Premack & Woodruff, 1978). However, a series of recent experiments with chimpanzees shows that at least a basic capacity to represent the knowledge of others is present in apes (Bräuer, Call, & Tomasello, 2007;Call & Tomasello, 2008;Hare et al, 2000), and very recent data based on eyetracking suggests a capacity to represent false beliefs as well (Krupenye et al, 2016).…”

‘Theory of mind’ in animals: ways to make progress

“…For the 'competitive paradigm', the same reasoning holds (Povinelli and Vonk 2004;Lurz 2009;Karin-D'Arcy and Povinelli 2002). For a scrub jay to re-cache the worms most at risk of being stolen, it can remember what competitors know about its cache locations, or it can recall which competitors were visible when it was caching, and how far away those competitors were (Penn and Povinelli 2007). Thus, in these experiments, subjects can always succeed by reasoning from what they themselves have seen, to what they themselves should do, without considering the mental states of others.…”

“…One reason skeptics give to interpret the results outlined above as insufficient evidence of 'theory of mind' is that they come from 'the wrong kind of experiment' (Hurley and Nudds 2006;Lurz 2009;Penn and Povinelli 2007;Heyes 1993Heyes , 1998Vonk 2003, 2004). According to this claim, all experimental setups reported in the literature are fundamentally incapable of establishing whether animals can reason about mental states, or only about behavior.…”

“…The first is that results that seem to indicate 'theory of mind' come from experiments that are of the wrong kind, that cannot differentiate between 'mind readers' and 'behavior readers' (Lurz 2011;Penn and Povinelli 2007). The second is that results come from experiments that are insufficiently controlled, in the sense that they do not explicitly test for alternative, 'less mentalistic' explanations (Bolhuis and Wynne 2009;Heyes 2012).…”

“…However, opinions differ on the interpretation of these findings. Some reviewers draw the conclusion that some animals 1 , at least, understand some mental states (Lyons and Santos 2006;Emery and Clayton 2009;Premack 2007;Seed and Tomasello 2010;Byrne and Bates 2010); others find the evidence unconvincing (Penn and Povinelli 2007;Lurz 2011;Shettleworth 2010a;Bolhuis and Wynne 2009;Barrett 2010;Shettleworth 2010b;Penn et al 2008;Lurz 2009). …”