Left-Hand Gestures Advantage on Metaphor Explanation: Evidence for Gestures’ Self-Oriented Functions Paraskevi Argyriou & Sotaro Kita School of Psychology, University of Birmingham. E-mail: PXA180@bham.ac.uk, S.Kita@bham.ac.uk Background Results Rationale: Differential hemispheric lateralization for linguistic processes determines the hand choice for gesturing. •Left-hand choice for gesturing increases when explaining metaphorical compared to literal expressions (Kita et al., 2007) (following the Right Hypothesis for Metaphor; Brownell et al., 2007). Aim: Do gestures activate cognitive processes in the contra-lateral hemisphere such that left-hand gestures activate metaphorical thinking? N= 31, adult right-handed males 1.60 Average Metaphoricity in speech •Gestures have communicative functions and facilitate listeners’ comprehension (Hostetter, 2011). •Gestures have self-oriented functions and enhance speakers’ cognitive processing (Kita, 2000). But, the exact mechanism for gestures’ self-oriented functions is not yet clear. 1.50 1.40 1.30 1.20 1.10 1.00 0.90 0.80 0.70 0.60 LeftHandGesturing • • • • NoGesturing RightHandGesturing Main effect of gesturing hand (F(1,30)= 13.92, p< .001). Left-hand Gesturing > Right-hand Gesturing (p< .05). Left-hand Gesturing > No-Gesturing (p< .001). Right-hand Gesturing > No-Gesturing (p< .05). 1 Left-hand gesture advantage on metaphor explanations Hypotheses •Metaphor explanation will be enhanced when speakers gesture with the left compared to the right hand. •The left-over-right-hand gesture advantage will be positively correlated with the right-hemisphere involvement for metaphor as measured by the mouth asymmetry. -1 0.8 0.6 0.4 0.2 0 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 -0.2 -0.4 Left-side mouth bias during metaphor explanations Methods Task: Interpret the metaphorical as opposed to literal meaning of • expressions, and explain the cross-domain metaphorical mapping (e.g., “to spill the beans is to tell someone something that you were not meant to tell; the beans represent the thing that was private and by spilling them you are telling it and revealing the secret to everyone”). Hand-choice manipulation: Right-hand gesturing, left-hand gesturing, • no-gesturing; participants encouraged to gesture. Left-side mouth bias significantly correlates with left-hand gesture advantage during metaphor explanations (r(30)= .379, p< .05). Conclusions Left-hand gesturing led to better metaphor explanation than right-hand gesturing. • The effect was larger for those whose metaphorical processing was strongly right-hemisphere dominant. •Gesturing with a particular hand activates processing in the contra-lateral hemisphere. Fig.1 Three gesturing conditions Fig.2 Three types of mouth openings Measurements: a) Level of metaphoricity in verbal responses on a scale from 0 to 2 (2= most metaphoric, 0= not metaphoric) (adapted from McGlone, 1996). b) Left-hand gesture advantage (Level of metaphoricity when Lefthand Gestured minus Right-hand Gestured). c) Left-side mouth bias during metaphor explanation (L-R)/(L+R+E), where L= number of left-dominant mouth openings, R= number of right-dominant mouth openings, E= number of mouth openings when both sides open equally (adapted from Holowka & Petitto, 2002). Comparisons: Levels of speech metaphoricity when Gestured Lefthand vs Gestured Right-hand vs Did not Gesture. Correlation: Left-hand gesture advantage and Left-side mouth bias. • Left-hand gesturing and right-hand gesturing both led to better metaphor explanation than nogesturing. •Gesturing activates spatial imagery, crucial to metaphor conceptualisation. References Brownell, H., Lundgren, K., Cayer-Meade, C., Nichols, M., Caddick, K., & Spitzer, J. (2007). Assessing quality of metaphor interpretation by right hemisphere damaged patients. Brain and Language, 103(1-2), 197-198. doi: 10.1016/j.bandl.2007.07.113 Holowka, S., & Petitto, L. A. (2002). Left hemisphere cerebral specialization for babies while babbling. Science, 297(5586), 1515-1515. doi: 10.1126/science.1074941 Hostetter, A. B. (2011). When Do Gestures Communicate? A Meta-Analysis. Psychological Bulletin, 137(2), 297-315. doi: 10.1037/a0022128 Kita, S. (2000). How representational gestures help speaking. In D. McNeill (Ed.), Language and gesture (pp. 162-185). Cambridge: Cambridge University Press. Kita, S., de Condappa, O., & Mohr, C. (2007). Metaphor explanation attenuates the right-hand preference for depictive co-speech gestures that imitate actions. Brain and Language, 101(3), 185-197. doi: 10.1016/j.bandl.2006.11.006 McGlone, M. S. (1996). Conceptual metaphors and figurative language interpretation: Food for thought? Journal of Memory and Language, 35, 544-565.