Cognitive load and working memory capacity; within and between modality
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Perceptual load and cognitive load have been assessed in the same method. However, it is proposed they have self-regulating and contradictory effects on the use of attentional resources. The difficulty of distinguishing between what is being measured is an on-going debate, centred on the allocation of limited capacity mental resources. The behavioural results from studies one and two, which looked at the reaction times to Relational Complexity based on visual, auditory and cognitive-based stimuli, underpinned the further EEG investigation based upon the differences in RT slopes over arity. RTs and errors were increased as relational complexity increased; Perceptual tasks (visual and auditory) divulge similar overall trends in RT performance, but are considerably slower and with less pronounced RT over arity slopes. This does not seem to be constant with the equivalent RT over arity slope found in the cognitive task. On these foundations, it can be concluded that the cognitive load defined by Halford is not only fundamentally different, but it may be differentiated from the effects of perceptual load measured in the analogous visual and auditory tasks. Results of the EEG experiments showed the visual RC based experiment responded well to alpha, across arity at occipital sites, as per hypothesis. The analogous auditory RC based experiment did not respond to either alpha or theta; this was not the expectation. The cognitive RC based experiment did not respond to alpha or theta, especially the latter, as synchronised FM theta over arity was expected, mainly as it was a ‘purely’ cognitive task. Limitations of the current study are discussed ranging from: issues of serially presented stimuli (auditory experiment), using time-frequency analysis, splitting up of frequency bands in lower and higher based Hz. The use of other imaging techniques namely: MEG, and the revaluation of the role of alpha in cognition. Suggestions for future research include the coupling of frequency bands and the Bayesian approach to statistical analyses.