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Living psychology: animal minds
Living psychology: animal minds

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6.2 Animal understanding of human goals and intentions

Read and consider the very influential study described in Box 2. It is especially significant because it was the study that first coined the term ‘Theory of Mind’.

Box 2 Premack and Woodruff: Does the chimpanzee have a Theory of Mind?

David Premack and Guy Woodruff (1978) were interested in whether chimpanzees showed evidence of understanding the goals and intentions of human beings. They argued that an understanding of human goals and intentions would constitute evidence of an animal having what they called a Theory of Mind. Premack and Woodruff explained this term as referring to an understanding of others and oneself as having mental states: ‘an individual has a Theory of Mind if he imputes mental states to himself and others’ (Premack and Woodruff, 1978, p. 515).

Premack and Woodruff saw ToM essentially as a ‘system of inferences’, and described it as a ‘theory’ because of two key observations: mental states are not directly observable (and hence need to be inferred); and the system (of inferences) is used to make predictions about an individual’s behaviour (a feature of theories is that they are often used to make predictions). The reasoning behind this study, which closely follows previous studies carried out with children, is that it is reasonable to take evidence of an understanding of another’s goals and intentions as an indication of possessing a ToM − that is an understanding that others have mental states.

The basic procedure used in this study was to show adult chimpanzees a series of videotaped scenes of a human struggling with a variety of problems − most involving inaccessible food. Some problems were relatively simple to solve, whereas others were more complex. For example, a simple problem involved a banana hanging out of reach of the human, and a box being available to step on to reach up to the banana. A more complex problem involved the human having to move a box, on which were piled several concrete blocks, in order to reach a banana − the heavy blocks had to be removed first, then the box could be moved to gain access to the banana. The video clips lasted 30 seconds and were played in front of the chimpanzees, but paused 5 seconds before the end so that the solution (to the problem of accessing the food) was not revealed. At this point the chimpanzees were presented with a pair of photographs, only one of which depicted the correct solution to the problem (e.g. placing and stepping on to a box to reach the banana). Figure 10 shows two of the photographs.

Described image
Figure 10 Photographs from the study by Premack and Woodruff (1978): (a) trying to get to an out-of-reach banana (above left); (b) the correct solution to the problem of reaching the banana (above right).

Essentially, what Premack and Woodruff found was that the chimpanzees were able to correctly choose the photograph that solved the problem of reaching the food, for nearly all the problems they were presented with in the videos. Premack and Woodruff believed that the chimpanzees’ consistent choice of the correct photographs indicated that the animals recognised the video as representing a problem, understood the human actor’s purpose (intentions and goals − their mental states) and chose the solutions that were compatible with the purpose. The chimpanzees’ ability to reliably pick the picture that solved the problem was seen by Premack and Woodruff as indicating that they attributed desires and intentions to others, and used these to make inferences and predictions about another’s behaviour: in this case, humans trying to solve a problem. This was taken as an indication that chimpanzees have a ToM.

Now have a go at answering the questions in Activity 12.

Activity 12 Do you agree with Premack and Woodruff’s interpretation?

Timing: Allow 10 minutes for this activity

Do you agree with Premack and Woodruff'’ interpretation of the findings of their study, which you have just read about?

Can you think of any alternative explanation for the chimpanzees’ behaviour that does not involve making such inferences?

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Discussion

Several philosophers independently made essentially the same key point about Premack and Woodruff’s study: that the chimpanzee may be solving the problem themselves, and thus choosing the correct photograph on this basis, without having to have any understanding of the human actor’s goals and intentions (Dennett, 1978). The important point made by these responses is that in order to assume that an individual observer (in this case the chimpanzee) is making inferences about another’s mental states, it is necessary that the observer’s own mental states − including goals, desires, intentions, and so on − do not match those of the other. If the observers themselves have the same mental states, then they could simply be interpreted as acting on their own intentions. Given the strong likelihood that the chimpanzees in Premack and Woodruff’s study would want to reach the banana, the solutions they chose could just be an indication that they can solve this type of problem for themselves. This explanation does not require any inferences to be made about the human actor’s intentions, goals or desires.

The Premack and Woodruff study has inspired a large body of research that has followed up on the essential question of whether animals have an understanding of other minds, or just act according to learned behaviours in response to environmental stimuli. This has led to various alternative procedures being designed in an attempt to assist in answering this question.

In a review article published 20 years after Premack and Woodruff’s landmark study, Heyes (1998) assessed the evidence on ToM in non-human primates and concluded that the studies carried out to that point did not provide any evidence of an understanding of others’ minds. In particular, Heyes pointed out that all existing studies were consistent with an interpretation in terms of either ‘behavioural rules’ (learned behavioural responses to stimuli) or an understanding of others’ mental states. Because of that ambiguity, it was not possible to draw clear inferences about which of these may underlie animals’ observed behaviours. Heyes, in 1998, urged that there was a need for studies that could distinguish between these two possible interpretations. There would be little point, she argued, in producing further observations of animal behaviour that would be consistent with both accounts if researchers wished to learn more about whether animals do indeed possess a ToM.

More recently, 10 years after Heyes’ (1998) review, Call and Tomasello (2008) presented an updated review of studies of ToM in chimpanzees. Considering a range of different types of studies, they came to the conclusion that the evidence so far did strongly suggest that chimpanzees have at least some understanding of others’ minds.

In the next sections of this course, you will learn more about some of the studies that have been conducted on this topic, starting with some designed to look at whether chimpanzees understand perception and knowledge, i.e. that others have visual perspectives that influence what they come to know and believe. As you will discover, the evidence suggests that chimpanzees do display some such understanding, but that it is limited compared with what very young human children have been shown to understand.