Masked stimuli modulate endogenous shifts of spatial attention

Recent evidence that attention is necessary, but not sufficient, for conscious perception

Early descriptions of attention in the psychological literature highlighted its interdependence with conscious awareness. As the study of attention developed, consciousness and attention began to be considered separable phenomena, experimentally and theoretically. In recent years, an energetic debate has developed concerning the extent to which the two phenomena are related. One school of thought considers the two to be doubly dissociable, whereas the other considers them to be necessarily linked. In this review, we highlight experimental findings from the last 5 years that contribute to the leading consensus view: attention is necessary, but not sufficient, for conscious perception. We review studies that show attention operating in conjunction with unconscious information, and other evidence linking attention necessarily to conscious perception. By drawing upon evidence that attention comprises many cognitive and neural processes, we argue that by studying how different forms of attention are related to conscious perception, it is possible to gain new insights about the neural states or processes that are necessary for conscious perception to occur.

Subliminal or not? Comparing null-hypothesis and Bayesian methods for testing subliminal priming

A difficulty for reports of subliminal priming is demonstrating that participants who actually perceived the prime are not driving the priming effects. There are two conventional methods for testing this. One is to test whether a direct measure of stimulus perception is not significantly above chance on a group level. The other is to use regression to test if an indirect measure of stimulus processing is significantly above zero when the direct measure is at chance. Here we simulated samples in which we assumed that only participants who perceived the primes were primed by it. Conventional analyses applied to these samples had a very large error rate of falsely supporting subliminal priming. Calculating a Bayes factor for the samples very seldom falsely supported subliminal priming. We conclude that conventional tests are not reliable diagnostics of subliminal priming. Instead, we recommend that experimenters calculate a Bayes factor when investigating subliminal priming.

Only pre-cueing but no retro-cueing effects emerge with masked arrow cues

The impact of masked stimulation on cognitive control processes is investigated with much interest. In many cases, masked stimulation suffices to initiate and employ control processes. Shifts of attention either happen in the external environment or internally, for example, in working memory. In the former, even masked cues (i.e., cues that are presented for a period too short to allow strategic use) were shown efficient for shifting attention to particular locations in pre-cue paradigms. Internal attention shifting can be investigated using retro-cues: long after encoding, a valid cue indicates the location to-be-tested via change detection, and this improves performance (retro-cue effect). In the present experiment, participants performed in both a pre- and a retro-cue task with masked and normally presented cues. While the masked cues benefitted performance in the pre-cue task, they did not in the retro-cue task. These results inform about limits of masked stimulation.