Change Blindness: Can perception occur in the absence of attention and awareness?

Many theories of perception argue that in the absence of focused attention our mental representations become ephemeral, and representation of change becomes impossible. In contrast, Ian Thornton and I have shown that changes that are neither explicitly detected nor attended to can nonetheless influence subsequent behavior [1]. People can ‘guess’ the location of changes even when they are not aware of those changes. A lively debate followed our initial report [2], but recently published data from our lab have answered many of the challenges leveled against our original findings.[3] We have also found evidence for implicit representation in our ERP study of change blindness.[4] In that paper, we also explored the relation between perceptual awareness and focused attention. In a complex visual scene, awareness of change necessitates the presence of focused attention. However, as our study revealed, attention and awareness are separable at the neurophysiological level.

To further explore the relation between attention and perceptual awareness, I conducted several case studies of brain-injured patients. In a split-brain patient, I have found a dissociation between object recognition and object localization: Despite the patient’s inability to verbally report the names of objects presented briefly to his left visual field, he can report their location, possibly by orienting attention toward the abrupt onset.[5] In two patients with bi-parietal hypoperfusion due to posterior cortical atrophy, I have uncovered early signs of simultanagnosia: The patients are capable of recognizing simple shapes when displayed sequentially, but not when displayed simultaneously.[6]

More recently, I have been using change blindness as a probe to study metacognition (i.e., people's belief about visual skills)[7].

Example will be here

find the change in the scene

Change Detection Database 

a good resource for those interested in change blindness

[1]Fernandez-Duque, D., & Thornton, I. M. (2000). Change detection without awareness: Do explicit reports underestimate the representation of change in the visual system? Visual Cognition. 7, 324-344.

[2] Mitroff, S. R., Simons, D. J., & Franconeri, S. L. (2002). The siren song of implicit change detection. Journal of Experimental Psychology: Human Perception and Performance,28, 798-815.

[3] Fernandez-Duque, D., & Thornton, I. M. (2003). Explicit mechanisms do not account for implicit localization and identification of change. Journal of Experimental Psychology: Human Perception and Performance.29, (5), 846–858.

[4] Fernandez-Duque, D., Grossi, G., Thornton, I. M., &  Neville, H. J. (2003). Representation of change: separate electrophysiological markers of attention, awareness, and implicit processing. Journal of Cognitive Neuroscience, 15(4), 1-17.

[5] Fernandez-Duque, D., & Black, S. E. (2002). Object localization without object recognition in the split brain: A possible role for spatial attention. Poster presented at the Visual Science Society annual convention, Sarasota, Florida.

[6] Fernandez-Duque, D., & Black, S. E. (2003). Early signs of simultagnosia in posterior cortical atrophy Poster presented at the Visual Science Society annual convention, Sarasota, Florida.

[7] Fernandez-Duque, D., & Black, S. E. (2002). Metacognitive knowledge and error detection in fronto-temporal dementia. Poster presented at the Psychonomic Society annual convention, Kansas City, Missouri.