When considering the results of research that has focused on a certain animal’s socio-cognitive abilities, an audience might wonder whether these findings suggest
that this particular species has a theory of mind. ‘Theory of mind’ is a term that was coined three decades ago by Premack and Woodruff (1978) and is defined as the
ability to attribute mental states, such as beliefs, desires, and intentions, to others and
to oneself. While the focus of my research was not whether lemurs have a theory of
mind, and a satisfying response is outside the scope of a PhD dissertation consisting
of six experiments, I will briefly address this issue.
My research explored whether lemurs use visual attention of others to modify
their own behaviour. The understanding of visual attention is believed to be an
important component of theory of mind, without which it might be impossible to
understand mental states such as intentions, knowledge, and beliefs in others (Baron-
Cohen, 1991; Kummer et al., 1996). One of the most debated questions, then, is
whether non-human primates are able to interpret another individual’s direction of attention as an overt behaviour resulting from the internal and, thereby, invisible
mental state of seeing (e.g. Povinelli et al., 2003).
It has been argued that it is possible to understand another individual’s visual
perspective without understanding his “mental perspective” (Byrne & Whiten, 1992),
and my data cannot provide evidence that anything aside from visual perspective
taking is the case for lemurs. It is possible lemurs can appreciate the relationship
understanding the attentional experience of another individual (Horton & Caldwell, 2006). Another individual’s direction of attention, and the relationship it has to
objects or events in the environment, can be used to give a “primitive” psychology –
to make sense of past actions and predict future actions, without needing to
understand or invoke the mental states of seeing, belief, or knowledge associated with
theory of mind (Baron-Cohen, 1994). This is achieved simply by understanding that
attention is directed towards targets, that attention is determined by gaze direction,
and that individuals usually act upon (or react to) objects to which they are attending
(Baron-Cohen, 1994; Gómez, 1996). This “aboutness” of gaze is a way to deal with
the causal link of attention to objects without needing to attribute mental states to
others (Gómez, 2005b). A mechanism like this one, however, should not be viewed as
vastly inferior to a theory of mind system, as both mentalistic and non-mentalistic
interpretations of gaze-object relationships allow an individual to appropriately navigate and manage its social environment and require a great deal of cognitive skill.
Responding to a relation between gaze and targets may already, however, be
an adaptation to one primitive, but key, feature of mentalism – so-called
“intentionality,” defined as the property of mental states to be directed at or point to
something other than themselves (Dennett & Haugeland, 1987). Adaptations to “see”
others’ gaze (an overt behaviour) as directed to targets may have been a starting point
for more complex adaptations to code intentional relations in terms of covert mental
states (Gómez, 2008).
In experiment 5.2, I found that lemurs preferentially acted on targets to which
other individuals attended. I proposed a mechanism called “gaze priming” to account
for this behaviour: a stimulus in the environment becomes more salient to an observer after another individual directs its attention toward it, and, as a result, the observer
acts differentially in response to that object. As environmental and social context can influence the precise way in which an individual would respond, the observer does not
need to reason about the intentions or belief of that other individual in order to
respond appropriately. This is a mechanism on which higher-levels of social cognition
such a mental state attribution could be built, but these higher-levels are not necessary
for that individual’s success in coping with social information. This fits nicely with
the ideas presented above: although mental state attribution can be a useful skill for
leading a life in a social group, it is not the only way in which an individual can
effectively discover, learn about, and respond to stimuli in the environment.
Tomasello and colleagues (2003) suggested that theory of mind is not black-
or-white, yes-or-no. Instead, it could be viewed as an umbrella term that covers a
wide range of socio-cognitive processes. The task becomes, then, to focus on
questions that are more specific than “Does animal Y have a theory of mind?” Instead, focus should be placed on the specific ways in which animals deal with the
social environment. I set out to explore the visual attention mechanisms lemurs use
when presented with various social cues. While my research shows that lemurs are
able to recognise and respond to the external behavioural manifestations of mental
states, such as direction of attention, these results cannot provide insight into whether
lemurs conceptualise those mental states when doing so. As I have argued, systems
that do not involve mental state attribution can be highly sophisticated and produce
similar (if not the same) results as a theory of mind mechanism.