Postural costs of performing cognitive tasks in non-coincident reference frames
Fraizer, Elaine Vida
An extensive literature exists attesting to the limited-capacity performance of\ud everyday tasks, such as looking and mental manipulation. Only relatively recently\ud has empirical interest turned towards the capacity limitations of the body\ud coordinations (such as posture control) that provide the physical substrate for\ud cognitive operations (and so mandatorily coexist with cognition). What are the\ud capacity implications for the body’s safety and mobility, for example, in\ud accommodating the need to stabilize the eye-head apparatus for looking, or when\ud mentally manipulating objects in 3-D space? Specifically, what are the postural\ud costs in having to position and orientate the body in its own task space while\ud supporting spatial operations in cognitive task space? What are the performance\ud implications, in turn, for everyday cognitive tasks when posture control is\ud challenged in this way? The purpose of this thesis was to establish a theoretical and\ud methodological basis for examining any postural costs that may arise from the\ud sharing or partitioning of spatial reference frames between these two components (a\ud frame co-registration cost hypothesis).\ud In 7 experiments, young adults performed either conjunction visual search or mental\ud rotation tasks (cognitive component) while standing upright (postural component).\ud Visual search probed cognitive operations in extrapersonal space and mental\ud rotation probed operations in representational space. Immersive visualization was\ud used to operationalise postural and cognitive task contexts, by arranging for the two\ud tasks (under varying postural and cognitive task-load conditions) to be carried out\ud with respect to two spatial reference frames that were either coincident or noncoincident\ud with each other. Aside from the expected performance trade-offs due to\ud task-load manipulations, non-coincidence of reference frames was found to\ud significantly add to postural costs for cognitive operations in extrapersonal space\ud (visual search) and for representational space (mental rotation).\ud These results demonstrate that the maintenance of multiple task-spaces can be a\ud source of interference in posture-cognition dual-tasking. Such interference may\ud arise, it is suggested, from the dynamics of time-sharing between underlying spatial\ud coordinations required for these tasks. Beyond its importance within embodied\ud cognition research, this work may have theoretical and methodological relevance to\ud the study of posture-cognition in the elderly, and to the study of balance and\ud coordination problems in learning difficulties such as those encountered in dyslexia\ud and the autistic spectrum.