Cognitive Processes PSY 334 Chapter 3 – Attention

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.

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.

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).

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.

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.

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.

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.

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.