Representational pseudoneglect: lateralised biases in attentional orienting in the absence of vision in healthy ageing participants.

Abstract

Pseudoneglect is the tendency to be biased towards the left side of space in tasks of a spatial nature. A non-visual form of the bias referred to as ‘representational pseudoneglect’ has been observed when people generate a mental representation of a stimulus in the complete absence of visual input - participants pay more attention to the left-hand side of the mental representation. The aim of this thesis was to advance our understanding of representational pseudoneglect by exploring the bias across lifespan using different modes of non-visual presentation (touch vs. audition vs. visual imagery). In Experiments 1 and 2 healthy participants aged 3 to 96 years used touch alone without vision to bisect wooden rods at the perceived centre. All participants (with the exception of some adolescents) showed leftward biases on tactile rod bisection and significant gender and age effects were found. In Experiments 3 to 10 healthy young adults listened to aural-verbal descriptions of abstract patterns or real-world scenes without vision and formed a mental representation of the spatial layout that was described. A leftward bias was consistently found for a relative judgement task along with a significant effect of monaural presentation and start side, but no lateralised bias for memory recall regardless of ‘mental mapping’ ability or method of response. In Experiment 11 participants eye movements were recorded while they visually processed and then memorised natural real-world scenes; again there was no lateralised memory or eye movement bias. Experiment 12 showed that a secondary task increased the magnitude of visuo-spatial pseudoneglect for children and adults under certain conditions. This thesis argues that purely representational forms of pseudoneglect clearly exist in healthy participants and that: 1) the results can be explained in terms of contralateral attentional orienting by the right hemisphere, 2) extraneous variables (gender; physical or imagined starting position) can mediate representational pseudoneglect, and 3) current models of cognitive ageing need to provide for a cognitive bias that can be enhanced by age.