Knowledge attribution

Knowledge attribution includes several forms of behaviour that are related to subject’s ability to “put itself in somebody's shoes”, or being able mentally to put itself in the place of others. This ability is based on perspective taking described above as well as discrimination of external manifestations of other’s intentions and desires such as gaze directions and body movements. Here we will consider several experimental paradigms aimed to test these abilities in animals.

Do animals know what others do and do not see? The criterion " seeing is knowing", as a part of knowledge attribution, is considered a minimum requirement for having a theory of others' minds.

To test whether or not chimpanzees meet this criterion, Povinelli and co-authors conducted series of experiments (Povinelli et al., 1992; Povinelli and Prince, 1998). One of them was done in two steps. In the first step a trainer came in and hid a reward under one of two cups, but since these were behind a screen the chimpanzee could not see under which one the food was hidden. Yet the chimpanzee could understand that it was hidden, as the trainer's hands were empty afterwards. Then the screen was removed so that the chimpanzee could see the cups. Another trainer came in and the two trainers each pointed to a different cup. The chimpanzee was only allowed to look under one of them. To begin with, the chimpanzees chose at random, but after a while they more often looked under the cup that the trainer who had hidden the food was pointing to. The long learning time agrees entirely with the results of Woodruff and Premack's experiment. The second phase of Povinelli's experiment began when the chimpanzees had learned to choose correctly in the first phase. Now both trainers were present when the reward was hidden behind the screen, but it was hidden by a third person. One trainer looked on passively, while the other had a bucket over his head so that he could see nothing. Just as in the first phase, the screen was removed, the bucket was lifted from the trainer's head, and the trainers each pointed to a different cup. Two of the four chimpanzees who were tested were able immediately to choose the cup pointed out by the trainer who had not had a bucket on his head. A third chimpanzee could manage it after a little training.

Povinelli and DeBlois (1992) repeated the second part of the experiment with children. From the age of about three, the children were able to choose the cup pointed out by the trainer who had seen where the reward was hidden. At earlier ages they chose cups more or less at random. A later experiment, however, casts a doubt on whether the chimpanzees' success was due to the ability to link " seeing" with " knowing". This experiment utilises the natural tendency of chimpanzees to beg for food by extending their hands. A chimpanzee sat behind a transparent screen, but it could stick its hand out through a hole towards the trainer. First the experimenters checked that the begging gesture worked by placing two keepers in front of the hungry chimpanzee, one of them with food, the other with a piece of wood. The chimpanzee understood the situation correctly and begged only from the keeper with the food reward. The experiment then went on to study whether the apes could distinguish a trainer who knew that there was food from one who did not know. One trainer was blindfold while the other had his mouth gagged. It turned out that the chimpanzees could not tell which of the trainer it was worth begging from. A number of variants of the experiment were tried. In one variant, one of the trainers held his hands over his eyes while the other had his hands over his ears; in another variant one trainer had a bucket over his head while the other had a bucket on his shoulder; in a third form the two trainers sat with their backs to the chimpanzee, but one of them was looking over his shoulder and could see the food. In none of these cases could the chimpanzees determine which trainer it was best to beg from. After continued training the chimpanzees were able to distinguish the trainers correctly. Yet it seemed as if the only significant factor was whether the trainer's face was visible or not; it did not matter whether the trainer's eyes were open or shut. Despite the successes in the first experiment, the probable conclusion is that the chimpanzees cannot clearly understand that " seeing is knowing".

Hare et al. (2001) devised a new test to examine whether chimpanzees know what other chimpanzees do and do not see. This test is based on the concept of social dominance that possibly makes a situation more natural. Two individuals, one dominant to the other, were placed in rooms on the opposite sides of a test room were food was positioned in different ways. They were then released into the test room to retrieve the food. For example, two pieces of food were placed between the subjects so that one subject could see only one of the food pieces (the food was hidden behind a small occluder). The results showed that subordinates preferentially retrieved food hidden from the dominant, while dominates preferentially retrieved food visible to the subordinate. In follow-up studies one subject was given a slight head start over the other. The delay forced subjects to decide which of the two pieces to approach before they saw where the competitor would go. Summarised results enabled researchers to conclude that chimpanzees know what conspecifics do and do not see and that they can use this information to formulate effective social strategies. Using the same experimental paradigm with capuchin monkeys, Hare et al. (2003) showed that capuchins perform differently with chimpanzees when competing for food. While subdominant capuchin monkeys are extremely sensitive to the behaviour of dominants, there was little evidence that they assess what conspecifics do and do not see when approaching and retrieving food (Fig. X-11).

Role-taking and role-reversion. Role-taking in animals was first experimentally tested by Pemack and Woodruff (1978). A language-trained chimpanzee, Sarah, was shown videotapes of human actors attempting to solve different problems – for example, attempting to escape from a locked cage, trying to obtain out-of-reach food, or to put a tape-recorder on by keystroke when the machine was out of plug.

The final image of each videotape sequence was put on hold, and Sarah was offered a choice of two photographs to place beside the video monitor. Both of these represented the actor in the problem situation, but only one of them showed the actor taking a course of action that would solve the problem. Sarah consistently chose the photographs representing problem solutions, and this was interpreted as evidence that she attributed mental states to the actor. It was argued that if Sarah did not ascribe beliefs and desires to the actor then she would see the video as an undifferentiated sequence of events rather than a problem (see Premack 1983, 2004).

Close examination of the published reports of the videotape experiments suggests that for any given problem Sarah could have responded on the basis of familiarity, physical matching and/or formerly learned associations. For example, when the actor was trying to reach food that was horizontally out of reach, matching could have been responsible for Sarah's success because a horizontal stick was prominent in both the final frame of the videotape and the photograph depicting a solution. Similarly, when the actor was shivering and looking wryly at a broken heater, Sarah may have selected the photograph of a burning roll of paper rather than an unlit or spent wick because she associated the heater with the red-orange colour of fire. Taken together, however, the results of Premack & Woodruff's videotape experiments are not subject to a single, straightforward nonmentalistic interpretation, and in this respect they are apparently unique in the literature on theory of mind in primates. Thus, according to this standard, no advance has been made on the original studies of theory of mind in primates (Heyes, 1993, 1998).

Povinelli et al. (1992 b) have shown that pairs of chimpanzees can reverse roles after being trained to perform complementary parts of a single task. This experiment involved ensuring that one chimpanzee was able to see where food was located but could not reach it, whereas the other chimpanzee was unable to see where the food was located but was in a position to reach it. Four chimpanzees were initially trained either to choose from an array of containers the one to which an experimenter was pointing (cue detection task), or to observe food being placed in one of the containers and then to point at the baited receptacle (cue provision task). Once criterion performance had been achieved on the initial problem, each chimpanzee was confronted with the other problem, and for three of the four animals this switch did not result in a significant decline in choice accuracy. This result was tentatively interpreted as evidence of " cognitive empathy" or " role taking”, that is, the ability to adopt the viewpoint of another individual. Povinelli et al. 1992 b). Using the same experimental procedure with rhesus monkeys, Povinelli et al. (1992 a) have shown that although monkeys coped well with the task each on its initial place, they did not match a criterion of “cognitive empathy”.

Further experiments with monkeys have brought mixed results, and some of them are positive regarding abilities of some species to infer several kinds of mental states, such as knowledge, goals, and intentions in others. In particular, monkeys were able to modify their behaviour according to another individual’s knowledge and intention. For example, capuchin monkeys were shown to be able to solve cooperative problems requiring different roles to be played by two players. Capuchins learned to discriminate between a “knower”, who inspected the box with food, and a “guesser”, who did not (Hirata and Matsuzawa, 2001; Kuroshima et al., 2002, 2003).

False-belief tests. Wimmer and Perner (1983) devised a false belief test, which was used to evaluate the ability of a subject to ascribe definite but false beliefs to another. Baron-Cohen et al. (1985) later simplified Wimmer and Perner's test so they could compare autistic, Down's syndrome, and normal children at different ages. As one of variants of this test, the Sally-Ann test (Baron-Cohen et al., 1985) is aimed to examine whether subjects express perspective knowledge and understand what others can and can not see. This test is presented as a simple story. There are two puppets, Sally and Anne. Sally has a marble, which she keeps in a basket. Then Sally leaves the room, and while she is away Anne takes the marble out of the basket and hides it in the box. Sally comes back into the room. The child subject is then asked the question: " where will Sally look for her marble? ". Older children say that she will look in the basket, because although they know the marble is in the box, they know that Sally doesn't know it has been moved from the basket, and they can distinguish Sally's (false) belief from their own (true) belief. Younger children, on the other hand, and autistic children, do not distinguish between the two. They simply say that Sally will look in the box. The false belief test, therefore, explores the change that happens as the common-sense development.

Research using the Sally-Ann test on language-taught chimpanzees aged between five and six years has shown that none passed the test (Call et al., 1994). However, Hauser (1998) developed an “ape version” of the test which he has used to test for a theory of mind in cotton-top tamarin monkeys and pre-verbal human children (about two years of age). The “ape version” involves a subject observing an actor watching where an object is hidden. When the object has been hidden a screen is raised to prevent the actor seeing another person moving the object to a different location but does not prevent the observer from seeing where the object is relocated. The screen is then removed and the actor either looks in the new location or the old location. Hauser reasoned that if an individual was aware that the actor could not know about the new location they should respond differently when they observe the actor looking in the new location and the old location. The observer with a theory of mind should spend more time staring at the actor who looks in the new location rather than the actor who looks in the old location. This is because the former violates the observer’s knowledge that the actor cannot know the new location due to the observer has not seen the object being moved. It turned out that both monkeys and pre-verbal children stare significantly longer when the actor looks in the new location than when the actor looks in the old location. This supports the author’s hypothesis that the subjects passed the test.