Johnson, Helen; (2003) The experience of action: Intention and attention. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

'Motor awareness' can be defined as any reportable knowledge available about a movement. This topic has received little attention from psychologists. This thesis aimed to establish suitable methods for measuring motor awareness. Two methods were developed; first, movement reproduction, a kinematic approach measuring the spatial details of participants' awareness, second, temporal judgements, a cognitive approach measuring awareness of movement duration. Both were found to be sensitive and appropriate measures. Movement reproduction was used in Experiments 1, 2 and 3 to investigate awareness of online corrections in pointing movements. In Experiment 1 slow, intentional corrections were reproduced accurately, whilst fast, automated corrections showed attenuated awareness. Anti point errors were an exception to this pattern. These automated corrections entered awareness as accurately as intentional movements. It was proposed that intention plays a major role in the extent to which a movement enters motor awareness and that errors also trigger a supervisory attentional system. Experiments 2 and 3 combined movement repetition with saccadic suppression. Perceptual and motor awareness were found to dissociate; participants reproduced movement corrections made in response to target jumps, even when perceptually unaware of the target jumps themselves. Experiment 3 attempted to disrupt online corrections with TMS, but no basic effect of TMS was found. Experiment 4 used a variant of temporal discrimination to investigate awareness of saccades. Again a dissociation of awareness was found, the intentional, planning component of the saccade entered awareness, whilst the automated component was subject to the chronostasis illusion. Experiments 5, 6 and 7 then combined Verbal Time Estimation with attentional cueing tasks. Participants were aware of the attentional effects on their RT when caused by endogenous cues, but not when caused by exogenous cues. Finally, a model was proposed in which motor awareness receives inputs from both an intentional system and error detecting circuits.

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