Temporal limitations of visual object processing
by McKeeff, Thomas J., Ph.D., PRINCETON UNIVERSITY, 2009, 111 pages; 3364543

Abstract:

The human visual system is surprisingly quick in some circumstances and stunningly slow in others. People can readily perceive a face, an object, or a scene within a single glimpse, yet detecting a target presented within a stream of successive distractors can prove to be quite difficult. What accounts for these temporal limitations in vision, especially with respect to object recognition? This dissertation uses psychophysics and functional magnetic resonance imaging (fMRI) to investigate the cognitive and neural processes that account for the limited temporal efficiency of object processing. Using rapid serial visual presentation (RSVP), I developed a method to measure temporal thresholds for recognizing objects. Subjects were presented with a successive stream of objects at varying temporal rates and had to discriminate which of two pre-specified targets appeared in the sequence. Behavioral results indicated that increasing the familiarity of an item led to faster processing, whereas increasing the visual complexity of an object did not impair the efficiency of object processing. Another experiment indicated that visual expertise with an object category affected the efficiency of object processing. Greater perceptual competition was found to occur between objects of expertise (i.e., cars and faces in car experts), suggesting that non-face objects of expertise rely on similar processing mechanisms as face processing. These effects of familiarity and expertise indicate that the temporal efficiency of object processing strongly depends on high-level knowledge acquired about objects. To explore the neural basis of these processing limitations, fMRI data were collected to characterize the temporal tuning properties of ventral visual areas implicated in object recognition. The preferred temporal rate of individual visual areas was found to decline at successively higher levels of the visual hierarchy, perhaps suggesting that recognition performance might be limited by the poor temporal capacity of high-level object-selective areas. However, the tuning in object-selective areas did not vary when preferred stimuli were intermixed with stimuli from a non-preferred category, indicating some discrepancy between behavioral performance and activity in these areas. Overall, the temporal processing limitation for recognizing objects appears largely dependent on object-specific processes, rather than limits at earlier stages of visual processing.

 
AdviserFrank Tong
SchoolPRINCETON UNIVERSITY
SourceDAI/B 70-07, p. , Aug 2009
Source TypeDissertation
SubjectsNeurosciences; Cognitive psychology
Publication Number3364543
Adobe PDF Access the complete dissertation:
 

» Find an electronic copy at your library.
  Use the link below to access a full citation record of this graduate work:
  http://gateway.proquest.com/openurl%3furl_ver=Z39.88-2004%26res_dat=xri:pqdiss%26rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation%26rft_dat=xri:pqdiss:3364543
  If your library subscribes to the ProQuest Dissertations & Theses (PQDT) database, you may be entitled to a free electronic version of this graduate work. If not, you will have the option to purchase one, and access a 24 page preview for free (if available).

About ProQuest Dissertations & Theses
With over 2.3 million records, the ProQuest Dissertations & Theses (PQDT) database is the most comprehensive collection of dissertations and theses in the world. It is the database of record for graduate research.

The database includes citations of graduate works ranging from the first U.S. dissertation, accepted in 1861, to those accepted as recently as last semester. Of the 2.3 million graduate works included in the database, ProQuest offers more than 1.9 million in full text formats. Of those, over 860,000 are available in PDF format. More than 60,000 dissertations and theses are added to the database each year.

If you have questions, please feel free to visit the ProQuest Web site - http://www.proquest.com - or call ProQuest Hotline Customer Support at 1-800-521-3042.