Chapter Four

1. Chapter Four The Cognitive Approach I: History, Vision, and Attention

2. Why a Cognitive Revolution? • Inadequate behaviorist accounts of language acquisition. Reinforcement cannot explain rapid learning of vocabulary and syntax. • New tools for measuring brain activity. • The rise of the computer as a metaphor for mind and the adoption of the information- processing perspective.

3. Cognitive Psychology • Neisser (1967) one of its early proponents. • The study of human knowledge representation and use. • Employs experimentation, modeling, and computer simulation. • Represents mental activity using a process model, a diagram with boxes and arrows that indicate information processing between successive stages.

6. Modularity of Mind • Mind consists of functionally independent modules (Fodor, 1983). • Modules are hardwired, domain-specific, fast, automatic, stimulus driven, and informationally-encapsulated. • E.g. reading • Deficit studies offer both positive and negative evidence of such modularity.

7. Perception • The process by which we gather and interpret information about the outside world via the senses.

8. Vision Two stages in vision • physical reception of stimulus • processing and interpretation of stimulus

9. The Eye - physical reception • mechanism for receiving light and transforming it into electrical energy • light reflects from objects • images are focused upside-down on retina • retina contains rods for low light vision and cones for color vision • ganglion cells (brain!) detect pattern and movement

11. Interpreting the signal • Size and depth • visual angle indicates how much of view object occupies(relates to size and distance from eye) • visual acuity is ability to perceive detail (limited) • familiar objects perceived as constant size (in spite of changes in visual angle when far away) • cues like overlapping help perception of size and depth

12. Interpreting the signal (cont) • Brightness • subjective reaction to levels of light • affected by luminance of object • measured by just noticeable difference • visual acuity increases with luminance as does flicker • Color • made up of hue, intensity, saturation • cones sensitive to color wavelengths • blue acuity is lowest • 8% males and 1% females color blind

13. Interpreting the signal (cont) • The visual system compensates for: • movement • changes in luminance. • Context is used to resolve ambiguity • Optical illusions sometimes occur due to over compensation

14. Ambiguity

15. Optical Illusions the Ponzo illusion the Muller Lyer illusion

16. Reading • Several stages: • visual pattern perceived • decoded using internal representation of language • interpreted using knowledge of syntax, semantics, pragmatics • Reading involves saccades and fixations • Perception occurs during fixations • Word shape is important to recognition • Contrast between text and background matters

17. Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it deosn’t mttaer in waht oedrr the ltters in a wrod are, the olny iprmoetnt tnihg is taht the frist and lsat ltteer be at the rghit pclae. The rset can be a taotl mses and you can slitl raed it wouthit porbelm. Tihs is bcauseae the haumn mnid deos not raed ervey lteter by istlef, but the wrod as a wlohe. Amzanig, huh?

18. Pattern Recognition • The ability to identify objects in the environment. • One of the main functions of perception. • There are many theories of how it takes place.

19. Template Matching Theory • An image generated from a stimulus is matched to an internal representation called a template.

20. The Pandemonium Model of Feature Detection

21. Feature Integration Theory • Used to explain visual search, in which we attempt to locate a target object hidden among distractors. • During the preattentive stage, features pop out effortlessly. Attention is not required. Search occurs in parallel. • During the focused attention stage features are combined together to create object representations. Attention is required. Search is serial.

22. Visual Search Parallel search Serial search

23. Attention • A form of mental activity or energy that can be distributed to different tasks. • Attention is: • Selective • Divisible • Shiftable • Sustainable

24. Theories of Attention • Bottleneck theories explain the narrowing of attention that enters conscious awareness. • Capacity theories explain how attention is distributed to different informational sources.

25. The Filter Model • Broadbent’s (1958) filter model of attention. • Information is selected on the basis of physical characteristics. • The selected information is allowed to pass to later stages where it undergoes further processing. • Unselected information is blocked completely. • An example of an early selection model.

26. The Attenuation Model • Formulated by Treisman (1964). • Unattended message is not blocked completely but attenuated. • The likelihood of information getting through is determined by its threshold.

27. The Deutch-Norman Selection Model • Attributed to Deutch and Deutch (1963) and Norman (1968). • Selection happens later in the attentional processing sequence. • It is therefore an example of a late selection model. • Selection is based on the semantic content of the message, its meaning.

29. The Multimode Model of Attention • Allows for selection to take place early or late. • The filter is “moveable” and can take place at various stages of processing based on the observer’s needs. • Selection can be based on physical or semantic characteristics.

30. The Capacity Model of Attention • Proposed by Kahneman (1973). • Attention is a limited resource. • Arousal level determines capacity. • Where attention goes is determined by enduring dispositions and momentary intentions.

32. Interdisciplinary Crossroads: Computational Vision • Marr (1982) specifies the steps a computer would go through to recognize an object. • Image is transformed into a raw primal sketch with a distribution of intensity values. • The 2 1/2-D sketch contains groups of features, surfaces, and layout. • The 3-D sketch is a three-dimensional interpretation complete with linked object parts.