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In press: In: Dimitrova-Vulchanova, M - NTNU

In press: In: Dimitrova-Vulchanova, M - NTNU

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Particularly interesting with respect to the encoding of these features are what we here<br />

label ‘verbs of biological motion’. The term ‘biological motion’ denotes the patterns of body<br />

and limb motion which animate creatures employ to achieve translational motion. Biological<br />

motion differs from non-biological motion in several ways (however, see Bejan & Marden<br />

2006 for a unified perspective on all motion). Its recognition and ex<strong>press</strong>ion in language is of<br />

paramount cognitive and social importance to human beings (Mandler 1996, Troje 2002). It is<br />

by definition self-agentive and involves the cyclic iteration of events of greater complexity<br />

(the cycles/patterns of internal motion of the body and limbs), the function of which is to<br />

cause translational motion (<strong>Dimitrova</strong>-<strong>Vulchanova</strong> 1996/99).<br />

A viable hypothesis of the factors that play a role in biological motion categorization<br />

can draw on evidence from research in visual perception. As it turns out, the human<br />

mechanisms of biological motion recognition are extremely robust. Biological motion can be<br />

recognized from strongly impoverished stimuli, for example when the moving figure is<br />

reduced to a point-light display (classical experiment in Johansson 1973, Giese 2004a, b).<br />

Furthermore, motion categorization is learning-based, perspective-dependent and selective<br />

(ibid). Giese & Poggio (2003) argue that the robustness of motion categorization resides in<br />

two neural pathways, each of them representing motion in a specific way: A form-pathway<br />

recognizes biological motion as a sequence of ‘snapshots’ of the figure in motion, and a<br />

motion-pathway recognizes biological motion as a sequence of optic flow patterns. While<br />

human action perception seems to tolerate substantial variation in form features (Giese 2004<br />

a, b), motion patterns seem to be specific to particular types of actions, which explains why<br />

biological motion can be recognized only through the motion pathway and in the absence of<br />

form information (e.g. in point-light displays). This theory of motion recognition enables us to<br />

hypothesize which criteria will be relevant in the categorization and linguistic encoding of<br />

biological motion. Criteria related to the form-pathway of recognition are body shape and<br />

proportions (e.g. bulky vs. slim body, short vs. long legs), characteristic use of limbs (e.g.<br />

biped vs. quadruped; the isolated movements of the limbs) and, by extension, also species e.g.<br />

human vs. non-human). The series of ‘snapshots’ in a particular temporal order is what we<br />

will call the cycle of a particular type of biological motion. Relevant factors, related to the<br />

motion pathway of recognition will be characteristic speed, path (the presence vs. absence of<br />

translational motion), basic path shape (underspecified vs. globally specified, cf. Nikanne &<br />

van der Zee 2005, <strong>Dimitrova</strong>-<strong>Vulchanova</strong> 2004a, b). The view dependence of motion<br />

recognition will predict that factors like figure orientation (e.g. front forwards vs. front<br />

backwards, head up vs. head down), relative vector orientation (towards vs. away from vs.<br />

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