Theses and Dissertations

Issuing Body

Mississippi State University


Williams, Carrick C.

Committee Member

Eakin, Deborah K.

Committee Member

Bradshaw, Gary L.

Committee Member

Swan II, J. Edward

Date of Degree


Document Type

Dissertation - Open Access


Cognitive Science

Degree Name

Doctor of Philosophy


College of Arts and Sciences


Department of Psychology


Perceptual categorization involves integrating bottom-up sensory information with top-down knowledge which is based on prior experience. Bottom-up information comes from the external world and visual saliency is a type of bottom-up information that is calculated on the differences between the visual characteristics of adjacent spatial locations. There is currently a related debate in municipal law enforcement communities about which are more ‘visible’: white police cars or black and white police cars. Municipalities do not want police cars to be hit by motorists and they also want police cars to be seen in order to promote a public presence. The present study used three behavioral experiments to investigate the effects of visual saliency on object detection and categorization. Importantly, the results indicated that so-called ‘object detection’ is not a valid construct. Rather than identifying objectness or objecthood prior to categorization, object categorization is an obligatory process, and object detection is a postcategorization decision with higher salience objects being categorized easier than lower salience objects. An additional experiment was conducted to examine the features that constitute a police car. Based on salience alone, black and white police cars were better categorized than white police cars and light bars were slightly more important police car defining components than markings.



police car||categorization||detection||visual saliency||perceptual categorization||object detection||object categorization