Visuomotor associations with highly manipulable objects: Effects of task and social context

Author: Liz Saccone

Saccone, Liz, 2017 Visuomotor associations with highly manipulable objects: Effects of task and social context, Flinders University, School of Psychology

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Abstract

Interacting successfully with the physical world is a fundamental skill for any animal. These interactions require tight coordination between vision and action processes, including rapid transformation of visual information into motor commands. To account for our remarkable ability to interact with the physical environment, modern cognitive neuroscience research has investigated how the human brain codes the objects around us. In particular, there is a drive to understand how sensorimotor processes and experience influence how we perceive the external world and how conceptual knowledge is acquired and stored within the brain. This thesis aimed to increase our understanding of these processing by addressing the following primary research question: In what ways are highly manipulable objects perceived and represented in motor terms in the human brain? The first chapters of the thesis introduce different theoretical perspectives on perception and cognition, including ‘embodied’ theories of higher-order cognitive processes and Gibson’s motor theory of visual perception. I review evidence from cognitive neuroscience and experimental, cognitive psychology that demonstrates motor neural resources are activated when highly manipulable objects are perceived and recognised. I introduce uncertainties surrounding the nature and role of this motor activation, which form the basis of the experimental work in this thesis. The remaining chapters detail experiments I conducted during my PhD, followed by a General Discussion. The thesis comprises a series of behavioural, object perception studies in which the action-relevant feature of object handle orientation (left/right) was manipulated. First, I investigated how a concurrent, unimanual motor task affected naming of lateralised objects to determine how competition for neural motor resources might impair object recognition. Results were inconsistent, both across my experiments and also compared with the published literature, and were therefore inconclusive. Accordingly, as a methodological adjunct, I investigated the convergent validity of vocal and manual response times in order to rule out inconsistencies owing to potential measurement problems associated with vocal responses. Results from a simple, attentional cueing paradigm suggested strong convergent validity between vocal and conventional, key-press responses. Next I investigated stimulus-response compatibility between left/right object handles and left/right key press response times. This well-established congruency effect (handle effect) is generally thought to reflect grasp-related motor activation. Alternatively, however, the effect can also be explained by abstract spatial compatibility between visually salient handles and lateralised manual responses. Three experiments ruled out this alternative explanation for the handle effect and have been published in the Journal of Experimental Psychology: Human Perception & Performance. The final experimental chapter describes a novel paradigm in which two humans perform an object recognition task in close proximity of one another. These experiments demonstrated that the handle effect can be modulated within shared, social space. I have proposed that this modulation relates to the way that near-body space is coded for both social- and physical environment-interactions. This chapter has been published in Attention, Perception, & Psychophysics. This thesis makes several contributions to our understanding of manipulable object coding and related visuomotor processes. First, findings highlight the limitations in using a dual-task, behavioural methodology to test the role of motor neural resources on object identification. Second, addressing the alternative explanation for the handle effect makes an obvious, important contribution to the relevant published literature. Third, results from my novel, social paradigm open considerable scope for future research into how social and space coding processes affect our interactions with the physical environment. Overall, these findings suggest that implicit motor activation evoked by manipulable objects represents an interplay between visuomotor processing of affordances, as well as internally stored motor information, acquired as function of our bodies’ capabilities and experience. Object-related motor information is activated flexibly in line with behavioural goals, responding quickly to environmental factors including social cues and context. This rapid exchange and integration of information undoubtedly accounts for our remarkable skill in interacting with the physical world.

Keywords: visuomotor processes, affordances, tools, object representation, peripersonal space, social space
Subject: Psychology thesis

Thesis type: Doctor of Philosophy
Completed: 2017
School: School of Psychology
Supervisor: Mike Nicholls