McCarthy, John Dylan; (1997) Changing attention. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

The focus of the thesis is to question how attention or selection bias might initially develop and change over time. In addressing this question it is argued that a linear information processing framework fails to account for the source or origins of selection bias. This issue has been ignored in the many selection paradigms because the source of bias is usually the experimenter. In other words, subjects are provided with a description of the target to select prior to the presentation of stimuli. Therefore, in this case, the question asked is how bias has its effect on subsequent processes rather than on the cause of bias in the first place. To break down this problem Posners' (1980) distinction between Endogenous and Exogenous factors is drawn on. Endogenous factors govern attention to internal goals whereas Exogenous factors govern attention to external circumstance. To account for these two sources of bias, a cyclic framework with two processing loops is proposed. By contrasting the proposed functions of the loops, it is inferred that a behavioural comparison needs to be made between biases towards familiar and novel objects. To investigate such selections empirically, a paradigm developed by Johnston et al. (1990) is adopted. Within this paradigm subjects are briefly presented with an array of four objects that must be identified and localised. If all the array objects are familiar then localisation performance is superior to when they are all novel. However, if a lone novel object is introduced into a familiar array then this pattern is reversed, showing superior localisation of novel, relative to familiar objects. This effect, known as Novel Popout, is examined in a series of six studies. The findings from the popout paradigm are used to develop a theoretical network model of the cyclic processing framework.

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