Target animacy influences gorilla handedness

Abstract

$"!We investigated the unimanual actions of a biological family group of twelve western lowland $#! gorillas (Gorilla gorilla gorilla) using a methodological approach designed to assess behavior

Social environment elicits lateralized behaviors in gorillas (Gorilla gorilla gorilla) and chimpanzees (Pan troglodytes).

“…Additionally, the exposure of the left side of the body toward conspecifics might better facilitate using the hand that is more involved in social interactions, as previously found in gorillas and chimpanzees. In these studies, animate targets elicited equal use of the left and right hands, indicating a higher proportion of left hand actions dedicated to animate compared with inanimate targets (see Forrester et al, 2011Forrester et al, , 2012. Second, the preference to keep conspecifics on the left side is likely to favor the positioning of the left side of the face toward other group members, as previously suggested by Baraud and colleagues (2009), to clearly show the arousal status and prevent extreme aggressive physical reactions.…”

“…handedness toward inanimate targets in primates, see Forrester et al, 2011Forrester et al, , 2012, and vigilance (Rogers et al, 2004). This type of asymmetric behavioral activity might have an adaptive value, facilitating simple reflexive and automatic responses to increase the survival of individuals (Rutherford & Lindell, 2011).…”

“…For gorillas, we employed two digital video cameras (Panasonic NVGS11B), one with a close view on the focal subject and one with a wider view of the surrounding social environment. Video footage was synchronized using a flash bulb (see Forrester, 2008;Forrester et al, 2011Forrester et al, , 2012Forrester et al, , 2013. Video streams were later compressed into a single file of 15 frames/s and composed by a top/bottom format for subsequent coding (i.e., focal view in the top and wide view in the bottom).…”

Slip of the tongue: Implications for evolution and language development

“…This sort of system supports perceptionaction coupling and may have acted as a catalyst for the emergence of syntactic processes found in modern human language (e.g. Forrester, Leavens, Quaresmini, & Vallortigara, 2011;Forrester, Quaresmini, Leavens, Spiezio, & Vallortigara, 2012;Tabiowo & Forrester, 2013). Such a processor also may have given rise to human population-level right-handedness (Annett, 2002), supported by the left hemisphere's dominance for guiding sequences of structured motor actions (e.g.…”

Human handedness: An inherited evolutionary trait

“…Consequently, the current study 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 10 employed a naturalistic behavior observation technique to investigate if handedness is influenced by context. We designed the study to methodologically match two previous studies on handedness conducted on two species of great apes: gorillas [89] and chimpanzees [90]. We simply questioned if the target of a manual action can influence the hand with which a child choses to interact with that target.…”