What can sequences of gestures tell us about cognition?

The analysis of individual gestures can reveal much about the meaning of specific signals, but does not take into account the dynamic environment in which gestures occur. It is difficult to consider the nature of a communicative act out with the context in which it was produced (most often an ongoing exchange between two individuals). In fact, it has been suggested that it is the interaction between individuals, rather than the behaviour of one party, that creates the meaning of particular actions (Griffin 1997; King 2004). In order to understand how gestures fit into interactions between orangutans, it is necessary to examine them as parts of the contexts in which they occur, taking into account the recipient’s as well as the signaller’s actions. Just as the identity of the recipient and the recipient’s behaviour prior to the gesture are influential in determining the form or success of a gesture, the recipient’s actions or reactions during a communicative exchange likely influence how the signaller gestures. In addition to responding to the behaviour of the other individual, orangutan signallers might also be influenced by the nature and success of their own communicative attempts, remembering what gestures they tried and how they were received. If an orangutan produces more than one gesture to another orangutan, it becomes possible to examine not only which gestures were used, but also whether the gestures were employed in predictable combinations and whether they were used to reiterate meaning or change meaning.

In evaluating signals of non-verbal individuals (i.e. infants and animals), a

persistent desire to communicate a goal and a diversity of methods employed in reaching it are the best indicators of intentional communication we have (Bates et al. 1979;

Golinkoff 1986; Lock 2001; Leavens et al. 2005). Sequences of communicative signals thus can provide better evidence of intentional communication than signals produced on their own. In addition to evidence of intentionality, sequences of gestures produced when

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a goal remains unfulfilled may allow us to evaluate the signallers’ communicative strategies, such as what they understand about the recipient’s state of mind.

To date, non-human gestural sequences have only been investigated in

chimpanzees. Two studies on the overall use of gesture by chimpanzees determined that chimpanzees often precede visual gestures with auditory or projectile gestures in order to attract the attention of the recipient who is not looking towards them (Tomasello et al. 1994; Leavens et al. 2004). However, a study of chimpanzee 2-gesture combinations found no evidence that chimpanzees used certain gestures to attract the attention of others before using visual gestures (Liebal et al. 2004). In all of these studies, the authors

assumed that gestures used sequentially were directed towards the same goal and communicated the same meaning, yet no evidence was ever presented to support this viewpoint. In an attempt to be objective, the analyses presented in this chapter were begun without any assumptions as to the functions of sequences. As in the analysis of individual gestures, I aimed to let the behaviour of the orangutans inform me about the meaning and use of sequences.

In order to determine what sequences of gestures indicate about the goals and decisions of the signaller, it is necessary to first investigate the circumstances under which sequences are produced—whether they are indicative of a signaller’s unfulfilled goals, or perhaps could be used to communicate different meanings than individual gestures. If orangutans use multiple gestures when the initial goal of the signaller has not been met, it would indicate that multiple gestures arise as a function of the persistent desire to achieve a specific goal. However, it is also possible that gestures are combined into sequences in order to convey a meaning that is different from that of any single gesture. If orangutans use multiple gestures to convey a persistent desire for a goal that has not yet been fulfilled, sequences should arise primarily when the recipient does not respond or responds in a way that does not fulfil the goal of the first gesture. Also, one would expect that gestures later in a sequence would have the same meaning as the first gesture. If, on the other hand, sequences are used to convey meanings beyond that of the first gesture, then the response of the recipient to the first gesture should not affect the

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likelihood of persistence and the gestures in the sequence would not necessarily have the same meaning as one another. If sequences of gestures were found to have different meanings from the gestures themselves, it would imply that orangutans have the ability to combine gestures according to some syntactic rule. The ability to combine meaningful communicative signals to create meanings distinct from those of the original signals has only been found in one non-human primate species (a monkey) (Arnold and Zuberbuhler 2006), and it is often speculated that certain elements of syntax represent the greatest difference between human language and non-human primate communication (Kako 1999; Hauser et al. 2002). Given the lack of meaningful (as opposed to phonological) syntactic elements in vocal communication systems of non-human primates, it is a priori unlikely that orangutans use sequences of gestures to create new meanings. However, to rule out this possibility, it is necessary to investigate under what circumstances multiple gestures are used, and whether gestures within a sequence most often have the same meaning as one another.

Orangutans might merely repeat their gestures if they do not achieve the desired response, or they may persist strategically, employing different types of persistence in different contexts. If orangutans use multiple gestures in situations where their initial goals have not been fulfilled, then when and how they persist may reveal what variables they take into account when choosing how to communicate. Signallers may choose to continue signalling in all cases where the recipient fails to meet their goals, or only in those cases where the recipient fails to respond at all. Provided sequences of gestures are used primarily in a continuing attempt to achieve an unaltered objective, the strategies signallers use in different social situations may provide insight into the orangutan’s ability to communicate in response to the behaviour, gaze, or knowledge states of others.

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