9-29 chapter6_Visual Attention_For Students

9-29 chapter6_Visual Attention_For Students - Chapter 6:...

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Unformatted text preview: Chapter 6: Visual Attention Overview of Questions • Why do we pay attention to some parts of a scene but not to others? • Do we have to pay attention to something to perceive it? • Does paying attention to an object make the object “stand out”? Attention and Perceiving the Environment • Divided attention - paying attention to more than one thing at one time – This ability is limited, which has an impact on how much we can process at once • Selective attention - focusing on specific objects and filtering out others Why is Selective Attention Necessary? • Some aspects of the environment are more important and interesting than others • The visual system has evolved to operate in this fashion – There is too much incoming stimulation at the retina to process everything – Selection is achieved partially through use of the fovea How is Selective Attention Achieved? • Scanning a scene - eye movements can take in different parts of a scene – Measuring eye movements - camera- based eye trackers show: • Saccades - small, rapid eye movements • Fixations - pauses in eye movements that indicate where a person is attending • Approximately 3 fixations per second What Determines Location of Fixations? • Characteristics of the scene: – Stimulus salience - areas of stimuli that attract attention due to their properties • Color, contrast, and orientation are relevant properties • Saliency maps show fixations are related to such properties in the initial scanning process • Bottom-up process that is unrelated to meaning Figure 6.5 (a) A visual scene. (b) Salience map of the scene determined by analyzing the color, contrast, orientations in the scene. Lighter areas indicate greater salience. ( Reprinted from Vision Research, 42, Parkhurst, D., Law, K., & Niebur, E., Modeling the Role of Salience in the Allocation of Overt Visual Attention, 107-123 (2002).) Eye Tracking Task (Ceballos & Komogortsev) Example of Initial Fixation (Ceballos & Komogortsev) Example of Initial Fixation (Ceballos & Komogortsev) Characteristics of the Scene • Picture meaning and observer knowledge – Scene schema - prior knowledge about what is found in typical scenes • Fixations are influenced by this knowledge • Influence of the observer’s task – Task demands override stimulus saliency – Eye movements are usually preceded by motor movements by fraction of a second Figure 6.6 Sequence of fixations of a person making a peanut butter sandwich. The first fixation is on the loaf of bread. (From Lord & Hayhoe, 2001.) When Can Perception Occur Without Attention?...
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This note was uploaded on 11/12/2009 for the course PSY 3321 taught by Professor Ceballos during the Spring '09 term at Texas State.

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9-29 chapter6_Visual Attention_For Students - Chapter 6:...

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