Cognitive Processes PSY 334

1. Cognitive ProcessesPSY 334 Chapter 3 – Attention

2. Neural Basis of Attention • Attention consists of enhanced neural response in a particular area of the brain. • The brain is organized topographically. • By increasing neural activity in a particular location, input to that location can be processed faster. • Specific details are “higher order” properties and take longer to recognize.

3. Iconic Memory • Visual sensory input can be remembered for a short time – up to 5 seconds. • Retention time varies if a post-exposure field is light (1 sec) vs dark (5 sec). • Following one display with another display “washes out” the first memory (icon). • Visual sensory information must be attended to and processed in order to be remembered longer.

4. Sperling’s Partial Report • The purpose of an icon is to retain an image until attention can focus upon it. • How long does the icon last? • How fast can attention move through it? • Subjects see an array of letters flashed briefly (50 ms), then report them back. • After the array is gone, a tone is sounded. • Subjects must report the letters in the row corresponding to the tone (high, med, low).

5. Feature-Integration Theory • Treisman – people must focus attention on a stimulus in order to synthesize its features into a pattern. • Feature integration takes much longer than simply recognizing a feature, especially with larger display sizes. • Single features can be identified without fixating upon them. • Illusory conjunctions occur when attention is not possible.

6. Visual Search • Treisman argued that search occurs based on a single feature. • When that feature is located, then the second feature is analyzed in that location. • Wolfe argued that two features can be searched for in conjunction (together). • Conjunction searches are noisier and less accurate than single searches. • Wolfe’s model requires direct attention too.

7. Visual Neglect • Visual neglect may occur due to damage to the posterior parietal lobe of brain. • People with such injuries have difficulty shifting attention from one side of visual field in order to look at the other side. • Cued attention tasks show one-sided deficit. • Visual extinction – when a competing object is present, the other disappears. • Unilateral neglect – one side ignored.

8. Object-Based Attention • Attention can be focused on particular objects, not just regions of space. • Sometimes it is easier to attend to an object (bumps on stimuli). • Inhibition of return – if we have already looked at a location it is harder to return to it. • Flickering squares take longer to identify because already viewed, even when rotated.

9. Object-Based Neglect • Just as objects can be attended to independent of their location, neglect can apply to objects, not locations. • Some patients neglect one side of objects regardless of which visual field they occur in.