Meanings

After comparing the effectiveness indices of the structural and social variables for the 9 gestures, I identified the variable that best predicted meaning in each gesture. Structural variables most effectively predicted observable goal in the gestures Grasp, Pull, Pull away, and Reach. Social variables most effectively predicted observable goal for the gestures Touch, Brush, Swat, and Push. The observable goal of the gesture Grab was best predicted by a structural variable when the goal was “share,” and by a social variable when the goal was “affiliate/play.” The gesture Push was also predicted to have two different goals once the additional variables were examined, but both goals were predicted by structural variables. Overall, structural variables were better predictors of observable goal than social variables were.

Of the 6 cases where structural variables best predicted the observable goal of a gesture, 4 were predicted by “target location,” 1 by “handshape,” and 1 by “hold.” Of the 5 cases of social variables most strongly predicting an observable goal, “relationship between signaller and recipient” was the most effective variable 3 times, “recipient’s behaviour” and “signaller’s age class” was each the most effective variable once. It seems clear that the target location of the gesture and the relationship between signaller and recipient are important variables in predicting the observable goal of gestures. This comparison is muddied slightly by the fact that the target location “food/object” accounted for 3 of the 4 cases where target was the best predictor of meaning. In all of these 3 cases, the observable goal was “share.” It seems reasonable that the target

location would be more important than other gestural variables in predicting that specific goal. Perhaps all gestures that touch an object held by another should be defined as a single gesture by their target location rather than grouped with other gestures through similarity of movement.

The comparison of the effectiveness index illustrates how both structural and social variables combine to create meaning and predict outcome. The structural variables “target” and “handshape” were both frequently able to predict the observable goals of

94

Appendices

gestures. The social variables “age of signaller” and “signaller’s relationship to recipient” were frequent predictors of observable goals as well. The recipient’s behaviour before the interaction was also able to control for some of the variance in meaning. Though it was only the most effective variable in predicting meaning once, the recipient’s behaviour before the gesture could be used to accurately predict an observable goal in 8 out of the 11 gestures analysed. This made it the most common, though not the most effective, predictor of meaning.

To most accurately interpret another’s meaning or to choose how to communicate most effectively, an orangutan must take into account both the form of the gesture and the nature of the preceding social interaction. I suspect that orangutans are monitoring both structural and social elements and are fairly sophisticated in their communicative strategies. Many of their gestures accurately predict one outcome when they are successful (i.e. when the presumed goal and outcome match).

In all, 6 different meanings were reliably predicted by gestures, and an additional meaning was predicted once further variables had been considered. Table 12 gives the gesture types associated with each meaning. The goals “pay attention to” and “pick up” were not accurately predicted by any gesture. It is likely that either there is no discernable difference between “pay attention to” and “affiliate/play,” or that the observers were not able to distinguish between the two. It seems reasonable that “pay attention to” should be added to “affiliate/play” rather than being counted as a separate goal.

Table 12: OBSERVABLE GOALS ACCURATELY PREDICTED BY SPECIFIC GESTURES. The gestures without shading were those that met the criteria for 70% use towards a single goal that was 3 times more common than the secondary goal. They are listed in order of total number of observations toward that goal. Gestures in shaded cells were ambiguous gestures for which a subset could be shown to accurately predict a specific goal once further variables had been considered. The “numbers accurately predicted” for the shaded gestures were those that increased the accuracy rate to more than 70% when one of the additional variables was taken into account. The column on the far right lists the additional variables that accurately predict specific goals for the ambiguous gestures. The table represents analysis of 639 gestural tokens.

95 Appendices Meaning (observable goal) Gesture Number accurately

predicted Additional variables for prediction?

Hit 28 Dangle 17 Wave 17 Hit ground 15 Bite 13 Pull hair 11

Duck lips open 11

Raise arm 9

Embrace 8

Fake 8

Simultaneous hit 8 Put object on head 6

Roll of back 6 Air bite 5 Play face 5 Raspberry face 5 Back roll 4 Shake 4 Arms up 4

Touch 7, 5, 5 Relationship, Handshape, Recipient _behaviour Grab 8, 5, 5 Relationship, Limb, Recipient behaviour Reach 11, 9, 8 Hold, Recipient behaviour, Age class Affiliate/Play

Swat 12, 9, 9, 8 Age class, Recipient visual attention, _{Relationship, Target}

Nudge 19

Shoo 12

Move back/Leave

Push 22, 21, 19, 21, 13, 7 Relationship, Target, Age class, Recipient visual attention, Handshape, Recipient behaviour

Food beg orally 5

Pull 13, 7 Target, Recipient behaviour

Grab 4 Target Share food/object Grasp 5 Target Tandem walk 7 Follow

Pull 11, 9 Target, Recipient behaviour

Climb on Embrace pull 6

Look at object Offer 5

Brush 7, 7, 6 Recipient behaviour, Relationship, Recipient _{visual attention} Stop

96

Appendices

Affiliation/play was far and away the most frequent goal and was associated with the greatest number of gesture types. Some of the gestures aimed at initiating affiliation or play are idiosyncratic (see 3.6.1) or used by only a few individuals and so the set of gestures used by most orangutans to initiate affiliation or play is only a subset of those listed in Table 12. Also, the goals “affiliation” and “play” were combined into a single goal because it was difficult to distinguish low-level play (i.e. not wrestling) from affiliation, and gestures associated frequently with one goal were also associated frequently with the other. The category represents a wide range of possible outcomes: from highly active play (wrestling), to sitting in contact, to manipulating objects together.