CHAPTER 4: USE OF GESTURAL SEQUENCES
4.3 Why use more than one gesture?
4.3.1 Do sequences reinforce or alter meaning?
In order to determine whether gestural sequences were strategic choices made when an initial gesture failed to receive the desired response, or were combinations of gestures that changed the overall meaning of the gestural utterance, I examined the consistency of meaning between the first and second gestures produced. Sequences in which the first and second gestures have the same meaning indicate that the signaller is probably persisting in an attempt to reach an initial goal rather than attempting to create a new meaning. If gestural sequences are an indication of persistence towards a goal, a high frequency of redundancy of meaning in the gestures should provide support for the
analysis of meaning of specific gestures used in this study (see Chapter 3).
I examined the meanings of the first and second gestures in sequences at least 2 gestures long (Table 21). I investigated the frequency of only those gestures determined to have predictable meanings (Table 8). The frequency of gestures with no consistent goal was noted, but as it was unclear what meanings (if any) these gestures had, they could not be used to determine whether the meaning of the second gesture matched that of the first. To analyse consistency of meaning in sequences, I ascribed meaning to each of the 29 high-fidelity gestures and the 7 low-fidelity gestures, which were identified in Chapter 3 by their consistent correlation with one observable goal (Table 8). For the purposes of this analysis, high and low-fidelity gestures were combined into one category of gestures that “predictably” had a single meaning. The gestures that failed to meet the criteria for prediction of a goal were recorded as having “no consistent goal.” It was assumed that these gestures were too infrequent to meet the criteria for predicting a goal, or were used frequently in more than one context.
Sequences beginning with the two most common meanings—“affiliate/play” and “move back/leave”—were analysed to determine whether the second gesture used had the same meaning or a different meaning. The frequency of meanings in second gestures was analysed for each individual for sequences beginning with both “affiliate/play” and “move back/leave.” The average number of sequences beginning with “affiliate/play” for
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each individual was 15.19 (± 17.55), and for “move back/leave” was 2.71 (± 2.05). The overall frequencies (across individuals) of these two meanings as first gestures in
sequences were 73% for “affiliate/play,” and 17% for “move back/leave.” The frequency of second gestures having the same meaning was analysed for individuals who exhibited at least 5 sequences beginning with “affiliate/play” and for those who exhibited at least 2 sequences beginning with “move back/leave.” This narrowing of the dataset was
performed to restrict analysis to only those individuals who had performed enough sequences to generate reliable frequencies of second meanings. As the average number of sequences per individual was only 2.71 for sequences beginning with “move back/leave,” the lower cut-off of more than one sequence was used in an attempt to avoid over- or underestimating proportions through lack of data. Expected frequencies for second gestures of both meanings were the same as their observed frequencies as first gestures. Sequences in which the second gesture was a repetition of the first were excluded from the analysis as meaning was, by definition, the same but could have been the result of excitement rather than indicating a choice of an equivalent gesture. A breakdown of the proportion of second gestures persisting in those meanings and the comparison to the expected frequencies is presented in Table 21.
Once repetitive sequences and individuals exhibiting fewer than 5 sequences beginning with “affiliate/play” or 2 sequences beginning with “move back/leave” were excluded, there were 203 sequences beginning with gestures meaning “affiliate/play,” 184 of which used a second gesture of the same meaning. There were 14 sequences beginning with gestures meaning “move back/leave,” 9 of which had second gestures of the same meaning.
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Table 21: MEANINGS OF FIRST AND SECOND GESTURES FOR EACH INDIVIDUAL IN SEQUENCES BEGINNING WITH GESTURES MEANING “AFFILIATE/PLAY” OR “MOVE BACK/LEAVE”
Each row describes the sequences produced by one individual. The percentage of second gestures with the same meaning as the first is calculated for each individual out of the total number of second gestures that were deemed to have a persistent meaning. Gestures with unclear or ambiguous meanings were not included in the calculation of frequency. The expected frequencies in the right hand column were taken from the proportion of meaningful first gestures that had the meaning “affiliate/play” (73%) or “move back/leave” (17%).
Second Gesture First
Gesture Same Different (ambiguous Unclear gestures) % same meaning (out of meaningful gestures) Greater than expected (73%)/(17%) 2 0 3 100% Y 3 1 1 75% Y 3 0 1 100% Y 5 0 0 100% Y 8 0 4 100% Y 13 2 13 87% Y 6 1 4 86% Y 13 0 8 100% Y 3 0 3 100% Y 6 1 1 86% Y 5 2 4 71% 21 0 5 100% Y 18 3 10 86% Y 5 1 2 83% Y 2 1 3 67% 5 0 1 100% Y 4 0 2 100% Y 17 3 18 85% Y
A
ffilia
te/P
la
y
45 2 15 96% Y 1 0 1 100% Y 0 1 2 0% 3 0 0 100% Y 2 0 0 100% Y 1 1 1 50% Y 1 1 1 50% YM
ov
e
b
ack
/lea
ve
1 1 3 50% Y137
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When the first gesture in a sequence was a gesture of the type “affiliate/play,” the average probability of the second gesture’s sharing this meaning was 91% (SD 11%). The second gesture had a different meaning only 9% of the time (SD 11%). For sequences beginning with “move back/leave” gestures, the second gesture had the same meaning 64% of the time (SD 38%), and a different meaning 36% of the time (SD 38%). Figure 5 compares the expected frequency of gestures meaning “affiliate/play” (73%) to the observed frequency (for each individual) of sequences starting with “affiliate/play” gestures containing second gestures with the same meaning. Figure 6 compares the expected frequency of gestures meaning “move back/leave” (17%) to the observed frequency (for each individual) of sequences starting with gestures meaning “move back/leave” containing second gestures with the same meaning. It is clear from Table 21, that second gestures (in sequences beginning with either meaning) were also frequently of a type that did not have a consistent meaning. Since gestures with low success rates, rare gestures, and ambiguous gestures were all included in the category of gestures with unclear meanings, it is impossible to determine whether cases in which the second gestures had unclear meanings are the result of meaningful gestures followed by gestures with different or multiple meanings, or followed by gestures the same meaning but which failed to meet one of the thresholds for the analysis of meaning.
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Figure 5: FREQUENCY OF SECOND GESTURES DUPLICATING MEANING OF THE FIRST FOR SEQUENCES BEGINNING WITH “AFFILIATE/PLAY.”
Each point indicates the gestural sequences produced by one individual. The dashed line represents the probability of a meaningful gesture having the meaning
“affiliate/play” based on the frequency of first gesture meanings (0.73). The solid line represents perfect concordance between the meanings of the first and second gesture, i.e. the distribution expected if the meaning of the second gesture were always the same as that of the first. Points that lie above the dashed line have an observed frequency greater than that predicted by the expected frequency of gestures meaning “affiliate/play,” those below it have an observed frequency less than the expected value.
P = 0.73 P = 0.73
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Figure 6: FREQUENCY OF SECOND GESTURES DUPLICATING THE MEANING OF THE FIRST FOR SEQUENCES BEGINNING WITH “MOVE BACK/LEAVE.”
Each point indicates the gestural sequences produced by one individual. The dashed line represents the probability of a meaningful gesture having the meaning “move back/leave” based on the frequency of first gesture meanings (0.17). The solid line represents perfect concordance between the meanings of the first and second gesture, i.e. the distribution expected if the meaning of the second gesture were always the same as that of the first. The larger point represents 3 individuals with equivalent values. Points that lie above the dashed line have an observed frequency greater than that predicted by the expected frequency of gestures meaning “move back/leave,” those below it have an observed frequency less than the expected value.
Since the majority of individuals used second gestures of the same meaning as the first more often than chance (i.e. their points lay above the dashed lines on Figures 5 and 6), data from all individuals was pooled for analysis of frequency. The mean frequencies of initial meaningful gestures having either “affiliate/play” or “move back/leave” as meanings were used as the probabilities that second gestures would exhibit those
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meanings (.73 and .17 respectively). Binomial tests were used to compare the observed frequency of same-meaning second gestures to the number expected by their frequency as first gestures. Second gestures matched the meanings of the first gestures significantly often both for sequences beginning with gestures meaning “affiliate/play” (Binomial test, n=203, p<0.0001) and sequences beginning with gestures meaning “move back/leave” (Binomial test, n=14, p=0.0001).
The second gesture in a sequence had the same meaning as the first significantly more often than was predicted by the frequency of both meanings as first gestures. This suggests that when orangutans use multiple gestures, they normally do so in an attempt to reach their initial goal. Since the meanings of first and second gestures in a sequence were more likely to reinforce than to contradict one another, it is reasonable to conclude that when gestures are used in a sequence it is usually with the intention of clarifying or emphasizing the original goal rather than combining gestures to create new meanings.