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Ula Cartwright-Finch, Nilli Lavie; Perceptual load induces inattentional blindness. Journal of Vision 2005;5(8):546. doi: 10.1167/5.8.546.
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© ARVO (1962-2015); The Authors (2016-present)
Lavie (1995, 2000) suggested that the processing of task-irrelevant stimuli depends upon the level of perceptual load in the relevant task. Conditions of low perceptual load leave spare capacity which spills over to irrelevant processing. Conditions of high perceptual load engage full attention leaving no capacity for any irrelevant processing. Support for the theory so far derives from indirect measures relying on distractor effects on RTs and visual cortex activity associated with distractor processing (see Lavie, 2005 for review). We report a series of experiments testing the implications of perceptual load theory for explicit awareness of task-irrelevant stimuli. The results show that the level of task-relevant perceptual load determines the extent to which observers are aware of an unexpected task-irrelevant stimulus or conversely exhibit Inattentional Blindness (Mack & Rock, 1998). Awareness reports for an unexpected stimulus (e.g. a square) presented in the periphery or at fixation on one final trial were significantly reduced during tasks of high perceptual load (e.g. a visual search task with six letters; a hard line-length discrimination task) as compared with tasks of low perceptual load (e.g. a visual search task with just one target letter; an easy color discrimination task). These results demonstrate that visual awareness as measured in inattentional blindness paradigms, critically depends upon the extent to which an attended task engages full capacity. They also rule out alternative accounts for inattentional blindness in terms of expectation or intention, as these factors were held constant across all levels of perceptual load in the current experiments.
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