Motivational aspects of explanatory understanding in humans and apes

J. Dutant, D. Justo, P. Pedrini

Povinelli (2000) argues that there are radical differences in explanatory understanding of physical objects between humans and apes. While we agree that empirical data support this claim, our present aim is to make it more precise. Our main point is that one has to distinguish two categories of abilities that account for this difference, namely motivational ones and cognitive ones. On the first count, Povinelli & Dunphy-Lelli (2001) experiments suggest that whereas only humans actively seek explanations, chimpanzees may still passively find explanations. On the second count, they may differ in their representational abilities, or in their reasoning abilities, or in both.  The conceptual distinction between these two categories opens the investigation into their phylogenetic relations.

Try-again systems and find-out systems

One can distinguish two ways in which a cognitive system deals with an unexpected event. We focus on cases where the unexpected event prevents the system to reach a goal.
A try-again system is a system that is motivated to explore other actions in the event of a failure. 
A find-out system is a system that is motivated to explore perceptual differences in the event of a failure.
These motivations will usually be associated with memory processes: if the goal is reached, the successful action or the spotted perceptual difference will tend to be stored in memory.
Each kind of motivation can be more or less complex. They can be automatic mechanisms that amount to following a rule of thumb such as “if you fail, try something else, and if that works, remember what you did” or “if you fail, look for a difference, and if you find one, remember it.” More complex try-again systems would be biased towards certain kinds of actions. More complex find-out systems would be biased towards certain kinds of perceptual differences, such as solidity rather than colour. 
This distinction can be made operational for empirical investigation. If an organism faced with an unexpected event displays a pattern of general exploration, it is a try-again system. If it displays a pattern of perceptual exploration oriented towards perceptual differences between the present situation and similar familiar situations, it is a find-out system. Yet, as Povinelli & Dunphy-Lilli (2001) show, one should carefully distinguish genuine find-out systems from try-again systems that are oriented towards perceptual novelty. In most situations in which an unexpected event is happening, there is a perceptible difference in the initial situation. This is the difference a find-out system aims at spotting. But this difference may also activate a general tendency to attend to perceptual novelties. A try-again system that has such a tendency will explore this difference just as a find-out system will do. Nevertheless, these alternatives can be discriminated by two control experiments. The first one is a situation where no perceptual novelty precedes an unexpected event. The prediction is that a find-out system will still look for a perceptual difference, whereas a try-again system will not. Povinelli & Dunphy-Lilli’s (2001) second experiment is of that kind, and suggests that chimpanzees are try-again systems whereas humans are find-out systems. The second control experiment is a situation where a perceptual novelty precedes an expected event. The prediction is that a try-again system will still look for one, whereas a find-out system will not.
Now, the point we want to stress is that this difference in motivation does not amount to a difference in cognitive abilities. A try-again system whose attention is drawn by perceptual novelty to potentially relevant perceptual differences could be able to represent these differences as reasons for an unexpected event, and reason about them. This has two consequences. First, the motivational difference is not relevant to the question whether “[non-human primates] are learning about underlying causal relations” (Povinelli & Dunphy-Lilli, 2001). Second, even if it is assumed that chimpanzees do not seek explanations, it is still open whether they find explanations, that is, whether they display explanatory reasoning without seeking explanations and if so, whether the cognitive aspects of explanatory reasoning differ in chimpanzees and humans. 

Representing explanations and explanatory reasoning

Explanatory understanding has a strictly cognitive aspect that differs from motivation. Hence a difference in explanatory understanding between the two species may be traced back to differences in cognitive abilities, besides a difference on the motivational aspect.
Two main kinds of cognitive abilities are involved in explanatory reasoning. On the one hand, there are representational abilities. These are the abilities specifically required for building representations. On the other hand, there are reasoning abilities. These are the abilities specifically required for using these representations in thought and action.
Representational abilities might differ in several ways, such as:
-	Differences in representational range. That is the range of properties that the organism can represent, such as shape, colour, weight and so on. 
-	Differences in the salience of properties. That is the degree to which it is easy for an organism to build a representation of a given property, when that property is within the representational range of the organism.
-	Differences in the salience of representations. That is the degree to which a given representation is accessible to mental systems that exploit it.
Similarly, reasoning abilities might differ:
-	Differences in the number of links. That is how many links between representations a cognitive process can build and keep stable while it occurs. Differences in working memory belong here.
-	Differences in the kind of links. That is, whether the links between representations are associative or inferential in nature.
-	Differences in the context-sensitivity of links. That is, the local or global character of the processing that establishes the links. Theoretical inferences would be a typical case of global inferences.
Povinelli (2000) makes several proposals to account for the differences in explanatory understanding that his experiments reveal: differences in salience, in the ability to represent unobservable properties, or in the theoretical character of human inferences. But in each of these aspects, a difference may obtain or not. That is why they should be carefully distinguished. For instance, the chimpanzees’ inability to solve certain problems involving weight can be interpreted in at least three ways: an inability to represent weight, an inability to keep a stable the representation of weight, or an inability to use this representation in inference. The resulting pictures of the chimpanzees’ mind would be radically different.
A further issue is to say what are the requirements to ascribe chimpanzees explanatory understanding at all. It is clear that being merely sensitive to correlations between properties is not sufficient. A starting point may be the difference between an organism’s being merely disposed to associate a representation to another one, and an organism’s being able to represent a relation between properties. This difference in representational range could be a minimal condition for an organism to have explanatory understanding. 
More generally, if, as is likely, chimpanzees and humans differ on many of these distinct aspects at the same time, these distinctions allow us to raise the question of their possible coevolution.

Conclusion

We argued that discontinuities in explanatory understanding between human and other primates may occur at a variety of levels. Making these distinctions allows a multi-factor characterization of differences in explanatory understanding and raises questions about the phylogenetical interdependency between these factors.

We are very grateful to Daniel Povinelli for useful discussion of these issues. 
References
Povinelli D. J. (2000) Folk physics for apes: the chimpanzee’s story of how the world works. Oxford: Oxford University Press. 
Povinelli D. J. & Dunphly-Lilli S. (2001) “Do chimpanzeeanzee seek explanations? Preliminary comparative investigations” Canadian Journal of Experimental Psychology, 55:2, pp. 187-95.