Sensation and Perception: Attention

Attention

• Attention is preferentially processing some stimuli at the cost of processing other parts
• Helps to perceive the attended stimuli better than the rest of the objects
• Needed because the perceptual system has a limited capacity and cannot process everything in the visual scene simultaneously

Types of Attention

• Overt attention: involves looking directly at an object
• Covert attention: involves looking at one object but attending to another object

Monitoring Attention

• Unless you purposely try not to, you tend to fixate the object to which you attend
• Fixate is when someone looks at an object
• What you fixate on depends on your goals and expectations
• Saccades are the ballistic eye movements between these fixations
• During saccades, you become temporarily blind

Directing Attention

• Two processes:
  • Initial involuntary process: mediated by attentional capture (e.g., sudden change on TV)
  • Subsequent voluntary process: guided by goals and expectations

Salience

• Determined by the salience of an image or object
• Salience is the quality of being noticeable
• What captures our attention:
  • High contrast (colour, luminance, size, orientation, motion/flicker)
  • Fixations are not only determined by goals but also expectations

Effects of Attention

• Speeds responses
• Influences appearance
• Influences physiological responding

The Binding Problem

• Different aspects of a stimulus are processed independently in separate brain areas
• Issue of how an object's individual features are combined to create a coherent percept
• Feature integration theory (FIT):
  • Suggests that this problem is solved by attending to only one location at a time
  • Features associated with that location are processed and bound together
  • Avoids binding features from different objects
• Illusory conjunctions: predicts that if attention is inhibited, features from different objects will be incorrectly bound
• Balint's syndrome: a patient with parietal lobe damage is prone to experiencing illusory conjunctions

Visual Search

• Some form of visual search is required for binding to occur
• Conjunction search: target object contains the same features as distractors
• FIT suggests that undivided attention is needed to understand each object's integration, making conjunction search slow
• Feature search: finding a target object with a unique feature that distractors don't have, making it faster

Change Blindness

• Attention determines what we remember
• We can only remember a part of the scene at a time
• If part of the scene changes, we may not notice it if attention is not drawn to the location of change

Learn about the role of attention in sensation and perception, including how it helps us process certain stimuli better while ignoring others.