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Bruce Bridgeman, Philip Tseng; Change blindness is reduced with responses that afford action. Journal of Vision 2009;9(8):1168. doi: 10.1167/9.8.1168.
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© ARVO (1962-2015); The Authors (2016-present)
Change blindness has been used to demonstrate the impoverished nature of visual representations. The verbal report measure in this paradigm underestimates information stored but not immediately available to consciousness because observers must be absolutely aware of changes and put them into words. Detection without awareness perhaps better assesses the true nature of visual representations. We tested whether the qualitative difference between cognitive and sensorimotor visual systems is reflected in implicit detection. Since the sensorimotor visual system is more implicit and does not rely on words, can it better access visual information when verbal report is not required?
Observers were randomly assigned to “cognitive” or “sensorimotor” groups. Both groups viewed 30 photos of natural scenes. On each trial a scene was displayed at a distance of 60cm, followed by a changed scene, without repetition. Observers reported the change on a 2×3 grid when they saw one ([[lt]]1%), or guessed the change location by trusting their “gut feelings” when a conscious detection was absent (99%).
In Exp 1, the cognitive group chose one of the grid blocks on the response screen. The sensorimotor group touched the monitor with a finger. Hit rates were reliably better in the sensorimotor condition. That is, in the absence of verbal change detection, observers could guess the location of change better when responding with a jab. The cognitive group, however, still performed significantly above chance level.
Exp 2 tested whether action affordance was critical to this sensorimotor advantage. The distance to the stimuli was extended to 3m, well beyond arm's reach, with angular size of the images kept constant. Participants pointed with a laser pointer; thus a jabbing motion could no longer afford any actions. The sensorimotor advantage disappeared in this distance condition. We conclude that visual representations are more effective for stimuli that afford action.
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