Reading Other Minds

Juliane Kaminski

19.1 Evolving a Theory of Mind

Humans have the ability to attribute mental states to others: that is, to attempt to predict others’ knowledge, desires, beliefs and their consequences. To summarize these capacities, Premack and Woodruff (1978) introduced the term “Theory of Mind” (ToM). They called it a “theory” as mental states are not directly observable and therefore need to be inferred. ToM‐related skills can be differentiated into three classes: understanding others’ perception (e.g., attention, visual or auditory perspective, etc.), understanding others’ motivation (e.g., others’ goals, intentions, etc.) and understanding others’ knowledge (e.g., others’ beliefs).

In recent years the question whether nonhuman animals, like humans, have social cognitive capacities became the focus of comparative cognitive research. From an evolutionary perspective, it is most likely that humans share some social cognitive skills, perhaps including mental state attribution, with other species. The so‐called “social intelligence hypothesis” formulated by Humphrey (1976) hypothesizes that cognitive capacities are most likely an adaptation to life in complex social groups. In fact, the more complex a social group’s structure, the more its constituent individuals can benefit from understanding the other group members’ cognitive states. This is because it will allow the individual to make flexible decisions depending on its understanding of the social relationships, and hence to adapt quickly to the constantly‐changing social environment. Later, the Machiavellian Intelligence hypothesis, formulated by Whiten and Byrne (1988), added competition as an important driving force for the evolution of social cognitive skills in social species. This hypothesis states that life in groups, and especially competition over resources, puts a constant selection pressure on evolving flexible cognitive skills. As there is a constant struggle to outwit competitors to monopolize resources, Whiten and Byrne hypothesized that social cognitive skills evolved in a kind of arms race between the evolution of measures to manipulate others and the evolution of countermeasures to avoid such manipulation.

If living in complex social groups is seen as the driving force for the evolution of social cognition, then we should expect to find social cognitive capacities, similar to humans’, in group‐living animals. In recent decades, an important question was therefore to what degree humans share our social cognitive capacities with other animals.

Humans can, in some situations, make predictions and inferences about others’ mental states. Humans can predict what others have or have not seen, what others desire, what they believe, and so forth—all often summarized as a “Theory of Mind” (ToM). While some researchers believe that reasoning about mental states is a uniquely human skill, others argue that humans share some social cognitive skills, including mental state attribution, with other species—notably our closest living relatives, the chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). From an evolutionary perspective, certain social cognitive skills would be beneficial for group‐living animals, as they are for humans. Following the Machiavellian Intelligence hypothesis, individuals with some knowledge about others, and the capacity to attribute mental states to others, would be in a better position to outwit their competitors; hence, group living should put a premium on the evolution of social cognitive skills that allow a more flexible understanding of others. However, there are many group‐living species, of which few, if any, are thought to have a capacity to attribute mental states to others. This raises the question whether other processes (e.g., associative learning) are sufficient to navigate social groups, even absent a full‐fledged ToM.

In order to study the evolutionary history of a certain skill, it is essential to compare the cognitive capacities of different species: For example, to investigate abilities that are particular to humans and our evolutionary history, we need to isolate those that are unique to humans amongst our closest phylogenetic relatives, the other apes. Any cognitive ability that is part of a shared repertoire between related species is likely to be part of their shared evolutionary inheritance from their last common ancestor. When it comes to the evolution of ToM‐related skills, the interesting question is whether a complex understanding of others is a widespread phenomenon in the animal kingdom, or whether it is a cognitive capacity unique to humans or shared only with a few other (perhaps closely related) species. While this question remains unresolved, evidence has recently accumulated suggesting that at least one ability—knowing when others can or cannot see things—may be a cognitive domain in which the capacities of some animal species are similarly flexible to those of humans.

19.2 Reading Others’ Attention

Eye‐shaped stimuli are important signals in the animal kingdom. One good example for the importance of eye‐shaped signals in the animal kingdom is the Peacock butterfly (Inachis io), which has eye‐shaped spots on its wings to scare away potential predators. These eyespots are an effective morphological antipredator adaptation that significantly increases individuals’ chances of survival (Vallin, Jakobsson, Lind, & Wiklund, 2005), suggesting that attention to eye‐like patterns is widespread and can be exploited. However, individuals from this species are most likely not aware that they have this signal. They have very limited control over its presentation to potential predators. They cannot modify the signal based on whether or not the potential predator is in a position to see them. The interaction between both individuals (prey and predator) can therefore be best explained as one example of a sender–receiver relationship in which one individual, the sender, presents a certain signal to which the other individual, the receiver, responds. The sender’s signals, as well as the receiver’s response, are fixed patterns, shaped by selection processes during evolution. The Peacock butterfly likely has no understanding whatsoever of the predator’s mental states.

However, there is evidence that for some species, the eyes signal something about others’ attentional states. All great ape species—including chimpanzees, bonobos, gorillas, and orangutans—adjust their gestural communication to the attentional state of a human experimenter. When the human is attentive (e.g., has her head turned towards the subject) they use more visible gestures (such as pointing or reaching) than when the human is not attentive (e.g., has her head turned away). Chimpanzees also use different types of gestures depending on the attentive state of the receiver. They use audible (e.g., hand clapping) instead of visible gestures if others are nearby, but not in a position to see them (Kaminski, Call, & Tomasello, 2004; Liebal, Call, & Tomasello, 2004; Liebal, Pika, Call, & Tomasello, 2004) and use visible gestures (e.g., pointing) when the other is in the position to see them and their eyes are visible (Hostetter, Russell, Freeman, & Hopkins, 2007).

Sensitivity to the eyes as an important signal for others’ attention seems to be widespread in the primate family. Rhesus monkeys (Macaca mulatta) and also ringtail lemurs (Lemur catta), for example, steal less food from a human experimenter whose eyes are open or directed toward them than from one whose eyes are closed or oriented away (Flombaum & Santos, 2005; Sandel, MacLean, & Hare, 2011).

Differentiating others’ attentional states is also not restricted to primates and seems to be present in species more distantly related to humans as well. Dolphins (Tursiops truncatus) produce more “pointing” (here defined as alignment of the body while remaining stationary for over 2 seconds) if a human is in a position to see them (e.g., oriented toward them) than when he/she is not (Xitco, Gory, & Kuczaj, 2004). Dogs (Canis familiaris) also show a high sensitivity to human eyes. When tested in a competitive situation with a human, in which the human forbade them to take a piece of food, dogs took more food when the human was oriented away from the food than when he was oriented toward it, or when the human’s eyes were closed as opposed to when they were open, or when the human was distracted as opposed to attentive (Call, Bräuer, Kaminski, & Tomasello, 2003). This was not only true in competitive, but also in more cooperative, contexts in which the dogs had to decide which human to beg from. Here, the dogs directed their begging more toward a human whose eyes were visible than toward a human whose eyes were covered (Gácsi, Miklósi, Varga, Topál, & Csányi, 2004). There is also evidence that different bird species are sensitive to a human’s attentional state. Sparrows and jackdaws attend to the presence of the eyes as well as the gaze direction of a human in a competitive situation related to food: When the human’s eyes were closed or averted, starlings resumed feeding earlier, at a higher rate, and consuming more, whereas jackdaws were responsive to subtle cues of attention, depending on the social context (i.e., whether the individual was a stranger or familiar to them) (von Bayern & Emery, 2009).

Overall, this shows that a certain level of sensitivity to the status of the eyes is relatively widespread in the animal kingdom among species very distantly related to each other. This could be an indicator that sensitivity to being observed might be an evolutionary ancient and relatively hard‐wired behavior with an urgent evolutionary function, but might also suggest that this trait is not homologous in all species and evolved as an analogous trait separately and several times in the animal kingdom.

19.3 Following Others’ Gaze

Many species from different taxa not only differentiate whether or not they are being observed, but also attend to where others are looking. For socially living animals, following the gaze of others is beneficial in order to gain information about outside entities. By following another’s gaze, the individual can get valuable information about different resources including food, predators, etc. One way to test for this behavior is to see whether an individual follows the gaze direction of another to a specific target outside its own field of view. Various primate species follow the gaze direction of other individuals. For example, all great apes species readily follow the gaze direction of a human experimenter (Bräuer, Call, & Tomasello, 2005). In this study, the human experimenter suddenly shifted her gaze toward the ceiling. Gaze‐following behavior in this situation was compared to a control condition during which the experimenter looked straight at the opposite side of the room. Apes looked at the ceiling significantly more often when the human had looked up than when she had not, indicating that they were sensitive to human gaze direction. The ability to follow others’ gaze is present not only in apes, but also in various monkey species more distantly related to humans. Emery, Lorincz, Perrett, Oram, and Baker (1997) showed that rhesus macaques were able to locate an object according to the gaze direction of a conspecific depicted on a TV monitor. Tomasello, Call, and Hare (1998) tested several monkey species (including Sooty mangabeys, Cercocebus atys torquatus; Rhesus macaques, Macaca mulatta; Stumptail macaques, Macaca arctoides; and Pigtail macaques, Macaca nemestrina) for their ability to follow the gaze of their group members. An experimenter, located in an observation tower, attracted the attention of one individual by presenting food to her. Once this individual had shifted her gaze toward the food, it was recorded whether a nearby subject (that had not seen the food itself) would respond with co‐orientation to the conspecific’s gaze shift. All monkey species tested in this setting followed the gaze direction of their conspecific. There is also evidence that different New World monkey species, like cotton‐top tamarins (Saguinus Oedipus), common marmosets (Callithrix jacchus) and different lemur species, are responsive to the gaze direction of others (Burkhart & Heschl, 2006; Sandel et al., 2011).

Gaze following is thus widespread among the primates. However, like attention reading, it has also been shown in a wide variety of other mammals including dolphins, seals (Arctocephalus pusillus), goats (Capra hircus), and dogs and wolves (Canis lupus). Dolphins and seals spontaneously attend to the gaze direction of humans (indicated by head direction) in a food search game (Scheumann & Call, 2004; Tschudin, Call, Dunbar, Harris, & van der Elst, 2001). Goats, like primates, follow the gaze of their conspecifics, and dogs seem to be especially sensitive to a human’s eyes and gaze direction (Kaminski, Riedel, Call, & Tomasello, 2005). Apart from the mammalian species tested, there also seems to be evidence that species even more distantly related to humans are sensitive to others’ gaze direction. Ravens (Corvus corax) and rooks (Corvus frugilegus) have been shown to follow others’ gaze direction. Ravens have been shown to co‐orient with the gaze of a human experimenter from an early age. In this test, a human experimenter shifted gaze (head and eye direction) up to a distant location to which the ravens responded with co‐orientation (Schlögl, Kotrschal, & Bugnyar, 2007). Recently it was also found that red‐footed tortoise (Geochelone carbonaria

Only gold members can continue reading. Log In or Register to continue