IPS 2008 N Scott


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Gesture use of chimpanzees: Effect of rank

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  • IPS 2008 N Scott

    1. 1. The Effect of Rank Nicole Scott & Stuart Semple Roehampton University IPS 2008: Edinburgh, UK Gesture Use of Chimpanzees ( Pan troglodytes ):
    2. 2. Communicating social rank <ul><li>Male charging display </li></ul><ul><ul><li>Pounding on objects & other chimpanzees </li></ul></ul><ul><ul><li>Stamping feet & charging </li></ul></ul><ul><li>Is it tailored to who is around? </li></ul><ul><li>Is it about volubility? </li></ul><ul><li>Is it aggressive? </li></ul><ul><li>Communicative style & rank </li></ul><ul><ul><li>What is the tie-in </li></ul></ul><ul><ul><li>Does it matter? </li></ul></ul>
    3. 3. Communicating through gesture <ul><li>Gesture – expressive movement of head/limbs and body postures used intentionally </li></ul><ul><ul><li>Two criterion: </li></ul></ul><ul><ul><ul><li>Sender directs a gesture towards a particular recipient </li></ul></ul></ul><ul><ul><ul><li>Flexible use of signs that distinguishes them from stereotypical behaviours and involuntary expressions of internal, emotional state </li></ul></ul></ul><ul><ul><ul><li>(Tomasello et al ., 1985) </li></ul></ul></ul><ul><li>Modalities </li></ul><ul><ul><li>Visual </li></ul></ul><ul><ul><li>Tactile </li></ul></ul><ul><ul><li>Auditory – excluding vocalizations </li></ul></ul><ul><li>Few studies on rank and gesture use in chimpanzees </li></ul>
    4. 4. Rationalizing gesture use <ul><li>High rank </li></ul><ul><ul><li>High salience of aggression & reassurance contexts </li></ul></ul><ul><ul><li>Benefit from drawing attention to self; afford costs of auditory gestures </li></ul></ul><ul><ul><li>Interactions with close ranked others maintains personal rank </li></ul></ul><ul><li>Low rank </li></ul><ul><ul><li>High salience of submission & greeting contexts </li></ul></ul><ul><ul><li>Attention to self may draw punishment; cannot afford cost of auditory gestures </li></ul></ul><ul><ul><li>Interactions with distant ranked others increases personal rank </li></ul></ul>
    5. 5. Aim & Predictions <ul><li>Aim : Find trends in gesture use according to social rank </li></ul><ul><li>The following hypotheses and predictions were derived and tested: </li></ul><ul><ul><li>Hypothesis (1) : Individuals use gestures associated with their rank </li></ul></ul><ul><ul><ul><li>the diversity of aggressive and reassurance gestures used by individuals will be positively related to rank, while the diversity of greeting and submissive gestures will be negatively related to rank </li></ul></ul></ul>
    6. 6. Predictions (cont.) <ul><ul><li>Hypothesis (2) : Auditory gestures are costly to produce </li></ul></ul><ul><ul><ul><li>the proportion of total interactions in which auditory gestures are given will be positively related to rank </li></ul></ul></ul><ul><ul><li>Hypothesis (3) : Gestures are used to govern social roles </li></ul></ul><ul><ul><ul><li>as rank difference between individuals increases, the proportion of interactions in which gestures are given will decrease </li></ul></ul></ul>
    7. 7. Methods <ul><li>Chester Zoo, UK – 30 chimpanzees </li></ul><ul><ul><li>Lived entire lives in Chester Zoo (exceptions) </li></ul></ul><ul><ul><li>Aged 2 years to 41 years </li></ul></ul><ul><ul><li>Analyses focused on adult only interactions </li></ul></ul><ul><li>Record by hand and video camera </li></ul><ul><ul><li>Focal animal and scan sampling </li></ul></ul><ul><ul><ul><li>30 minute sessions </li></ul></ul></ul><ul><ul><ul><li>Simultaneous ad lib recording </li></ul></ul></ul><ul><ul><li>9 hours per animal </li></ul></ul><ul><li>Observations between 1000 and 1700 hrs </li></ul><ul><li>March 1 to May 30, 2007 </li></ul>
    8. 8. Chester Zoo enclosure
    9. 9. Chester Zoo enclosure
    10. 10. Determining rank <ul><li># of wins in dyadic interactions </li></ul><ul><li>Interactions contexts include: </li></ul><ul><ul><li>One –sided greetings </li></ul></ul><ul><ul><li>Directed displays </li></ul></ul><ul><ul><li>Agonistic interactions </li></ul></ul><ul><li>Analyzed in Mat-Man 1.1 </li></ul><ul><li>Male & Female hierarchies assumed stable </li></ul>
    11. 11. How are gestures used? <ul><li>Hypothesis : Individuals use gestures associated with their rank </li></ul>High rank Low rank Aggressive gestures Reassurance gestures Submission gestures ‘ Greeting’ gestures Give gestures:
    12. 12. Diversity of gestures <ul><li>Shannon Index </li></ul><ul><ul><li>Spearman Rho </li></ul></ul><ul><ul><li>No significance for females </li></ul></ul>Males -0.900* 0.037 C.C. Sig. (2-tailed) Aggression 0.667 0.219 C.C. Sig. (2-tailed) Submission -0.300 0.624 C.C. Sig. (2-tailed) Reassurance -0.200 0.747 C.C. Sig. (2-tailed) Greet RANK CONTEXT
    13. 13. Evidence of male trends
    14. 14. In what forms are gestures given? <ul><li>Visual Auditory Tactile </li></ul><ul><li>Hypothesis : Auditory gestures are costly to produce </li></ul>Gestures given : Auditory gestures Social rank
    15. 15. Auditory gestures <ul><li>Spearman Rho </li></ul><ul><ul><li>Rank </li></ul></ul><ul><ul><li>Proportion of total interactions with gestures </li></ul></ul>0.861 18 0.044 Females 0.505 5 -0.400 Males Sig. N C.C.
    16. 16. No rank effect - Males No. of interactions
    17. 17. No rank effect - Females No. of interactions
    18. 18. What is their function? <ul><ul><li>Individuals interact more frequently with others of similar rank </li></ul></ul><ul><ul><li>Hypothesis : Gestures are used to govern social roles </li></ul></ul>Proportion interactions gesture given Difference in rank Same sex interactions :
    19. 19. Distance between ranks <ul><li>Spearman Rho </li></ul><ul><ul><li>Rank difference </li></ul></ul><ul><ul><li>Proportion interactions between dyad </li></ul></ul><ul><li>One Sample t-test </li></ul><ul><ul><li>Mean of correlation coefficients </li></ul></ul><ul><ul><li>Compare means to zero </li></ul></ul>0.564 17 0.588 Females 0.689 4 0.430 Males Sig. df t
    20. 20. Conclusions <ul><li>A portion of prediction (1) was supported </li></ul><ul><ul><li>Males of high rank use more aggressive gestures than low ranked males </li></ul></ul><ul><ul><li>No such result was found for females interactions </li></ul></ul><ul><li>Predictions (2) and (3) were not supported </li></ul>
    21. 21. What does it all mean? <ul><li>Rank has little effect on individual strategies of gestural communication </li></ul><ul><li>A relationship exists between an individual’s rank and the diversity of aggressive gestures in its communicative repertoire, at least in male chimpanzees </li></ul><ul><li>Communication style is more personal than socially assigned. </li></ul>
    22. 22. <ul><li>Joanna Bishop, Chest er Zoo </li></ul><ul><li>Clare Caws, Chester Zoo </li></ul><ul><li>Peter Litherland, Welsh Mountain Zoo </li></ul><ul><li>Prof. Frans B. M. de Waal </li></ul>Thank You! Any Questions?