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CHAPTER FOUR The Cognitive Approach I: History, Vision, and Attention.

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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 illusionthe 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 searchSerial search

23 Attention  A form of mental activity or energy that can be distributed to different tasks.  Attention is: 1. Selective 2. Divisible 3. Shiftable 4. 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. 1. Image is transformed into a raw primal sketch with a distribution of intensity values. 2. The 2 1/2-D sketch contains groups of features, surfaces, and layout. 3. The 3-D sketch is a three-dimensional interpretation complete with linked object parts.

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