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Title: Factors affecting target perceptibility in object substitution masking
Author: Argyropoulos, Ioannis
Awarding Body: Oxford Brookes University
Current Institution: Oxford Brookes University
Date of Award: 2013
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Object substitution masking (OSM) refers to the observation that reporting of a briefly presented target item is considerably reduced when a mask remains visible after the target offset. The size of OSM has been said to be critically dependent on the speed with which attention is deployed towards the target. One line of evidence in favour of this view is that when set size increases so does OSM. In addition, when the target location is known in advance because of a pre-cue OSM is reduced or eliminated. However, all the studies that reported an interaction between set size and OSM or between pre-cue and OSM performance was at ceiling/floor or there was no control condition. This might have led to an over-interpretation of the statistical interactions which were evidently a consequence of ceiling and floor effects in performance, or in other cases the failure to correct for clear response biases. In Chapters 2&3 the purported role of attention in OSM is investigated by manipulating orthogonally set size and mask duration. The principal finding is that, when performance is not influenced by ceiling/floor effects and the scores are corrected for response bias set size and mask duration do not interact although their individual effects are highly significant. Chapter 4 shows that the set size effect in OSM is not due to crowding; the two factors affect OSM independently. In Chapter 5 attention is manipulated in a direct manner by employing a spatial pre-cue and manipulating the cue-target onset asynchrony. Although pre-cueing the target improves performance it does not affect OSM. Finally, in Chapter 6 the participants phenomenal experience in OSM is investigated. The results show that at a relatively large number of masking trials OSM is “complete”; participants report seeing a blank space at the target location although the target is present. Collectively, the results of the present thesis show that attention does not influence OSM when it is controlled either indirectly (i.e. set size, crowding) or directly (pre-cue). What these findings show is that Di Lollo et al.'s specific implementation of the general model of the re-entrant account of awareness is invalid. The findings are also discussed in relation to other accounts of OSM , Moore and Llleras's (2003) object-updating account and Poder's (2012) attentional gating model (Chapter 7).
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available