Discuss different aspects of conscious awareness and how these aspects can be studied scientifically.

These results have proved to be highly controversial, and several studies have failed to replicate them. One focus of criticism has been Marcel’s criterion for determining the absence of conscious awareness (60% correct on presence/absence judgements).

According to Cheesman & Merikle (1984, P&P 36), there are two thresholds for conscious awareness: The subjective threshold is the point where subjects report to be unable to respond above chance, while the objective threshold refers to the point of chance performance in Forced Choice detection tests.

Cheesman & Merikle (1984) replicated the Marcel (1983) colour priming study, but determined the objective thresholds (25% correct prime detection).

While facilitation and inhibition for congruent and incongruent trials was found for longer prime durations, no priming effects were found when primes were presented at the objective threshold. In another experiment, subjective and objective thresholds were determined independently, resulting in prime word durations of 56 ms and 30 ms, and objective detection accuracy of 66% at the subjective threshold.

Priming effects were found for words at the subjective threshold, but not at the objective threshold. In spite of claiming otherwise, Marcel (1983) may have investigated subjective rather than objective thresholds.

Cheesman & Merikle (1986, CanJPsych 40) argued that objective thresholds constitute the ultimate limit for any effects of visual perception on discriminative performance, so that defining conscious awareness in terms of objective thresholds is to define unconscious or subliminal perception out of existence. In contrast, subjective thresholds capture the phenomenological difference between conscious and unconscious experience.

Information presented above and below the subjective threshold can have qualitatively different effects on performance, thus showing that the subjective threshold is functionally relevant.

Merikle & Joordens (1997) used the colour word priming paradigm with prime words presented below the subjective threshold (critical stimulus duration) or clearly visible primes (214 ms duration).

Only two different colours were used, and 75% of all trials were incongruent – there was a predictive relationship between prime word and the to-be-named colour. For primes presented below the subjective threshold, the usual colour priming effect was observed, with faster responses in congruent trials.

The opposite pattern was found with above-threshold stimuli! Visual information can be used in a strategic manner when it is consciously perceived, but not when it is presented below the subjective threshold.