SFU Canada Research Chairs Seminar Series: "To Be (Attended) or Not To Be (Attended): Recent research on attention capture from the SFU Human Electrophysiology Lab"
11:30 - 12:30
Rm10900
Dr. John McDonald, Canada Research Chair in Cognitive Psychology
Department of Psychology, Simon Fraser University
Abstract
When searching the visual environment for an object of interest, the presence of a salient-but-irrelevant stimulus creates competition for access to conscious awareness. This competition can be influenced by top-down attentional control strategies aimed at selecting relevant information and ignoring irrelevant information, as well as by bottom-up activation triggered by the stimuli themselves. It is unclear how - and at what processing stage - top-down strategies can override bottom-up activation to enable selection of relevant objects. Some researchers have proposed that top-down control can override bottom-up activation at preattentive stages of visual processing by suppressing information arising from the location of irrelevant objects. Others have proposed that top-down control can override bottom-up activation only after attention is deployed automatically to the most salient stimulus. We resolved this controversy using event-related potentials (ERPs) to pinpoint the processing stages at which distracting information can be suppressed. We show that, when confronted with a search display containing a target and a more salient distractor, observers suppress information arising from the distractor either early on or later on in the processing stream, depending on whether or not the observer has advance knowledge of the defining feature of the to-be-ignored distractor. When the colour of the distractor was predictable, the distractor was suppressed before it captured attention. When the colour of the distractor was unpredictable, the distractor was suppressed after it captured attention but before distractor information was transferred to working memory. The finding of early suppression is inconsistent with the notion that salient stimuli capture attention automatically and independently of top-down control.
About the Speaker
Dr. John J. McDonald completed his undergraduate degree in Psychology and Geography at Simon Fraser University in 1993 and his Ph.D. in Psychology at the University of British Columbia in 1999. In the period 1999 - 2000, Dr. McDonald was an NSERC Postdoctoral Fellow in Neurosciences at the University of California San Diego. He joined Simon Fraser University in 2001 as an Assistant Professor in the Department of Psychology. In 2004 he was awarded a Canada Research Chair in Cognitive Neuroscience. Dr. McDonald is also the Director of the Human Electrophysiology Laboratory at Simon Fraser University. As the Canada Research Chair, Dr. McDonald is shedding light on the neural underpinnings of attentional and perceptual processing in the visual and auditory modalities. In addition to studying the ways in which attentional and perceptual processes spread across the modalities, Dr. McDonald also investigates attentional processes within each modality. Current research projects involve visual search, inhibition of return, and the executive control of spatial attention. Among other scientific activities, Dr. McDonald has published multiple scientific papers and book chapters and gave presentations at numerous scientific conferences. Dr. McDonald together with his Ph.D. student Ms. Jessica Green have successfully used electroencephalography (EEG) to pinpoint, in space and time, the neural activities involved in paying attention. The pair used a signal-processing technique called beamforming, which was originally used for radar and sonar which enabled them to decipher the timing and sequence of brain activity coinciding with an individual's attention to different visual objects in his/her environment. Dr. McDonald and Ms. Green have high-hopes for future brain-function research using this new technique. In Dr. McDonald's words, "The ability to identify human brain activities in both space and time is an important achievement in cognitive neuroscience."
