1 Perception

2 Perception The process of selecting, organizing, and interpreting sensory information, which enables us to recognize meaningful objects and events.

3 Selective Attention Perceptions about objects change from moment to moment. We can only focus on limited aspects of sensory input at any given time e.g. : “Cocktail Party Effect”

4 Perceptual Illusions Illusions provide good examples in understanding how perception is organized. Studying faulty perception is as important as studying other perceptual phenomena. Line AB is longer than line BC.

5 Tall Arch In this picture, the vertical dimension of the arch looks longer than the horizontal dimension. However, both are equal. Rick Friedman/ Black Star

6 Perceptual Organization How do we form meaningful perceptions from sensory information? We organize it. Gestalt psychologists showed that a figure formed a “whole” different than its surroundings. called a “gestalt”

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8 Organization of the visual field into objects (figures) that stand out from their surroundings (ground). Form Perception Time Savings Suggestion, © 2003 Roger Sheperd.

9 Grouping After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules.

Our perceptions are a combination of sensory (bottom-up) and cognitive (top- down) processes. Our perceptions are a combination of sensory (bottom-up) and cognitive (top- down) processes. 10 Perception in Brain

11 Perceptual Interpretation Immanuel Kant ( ) maintained that knowledge comes from our inborn ways of organizing sensory experiences. John Locke ( ) argued that we learn to perceive the world through our experiences. How important is experience in shaping our perceptual interpretation?

12 Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars. Blakemore & Cooper (1970) Sensory Deprivation

13 (a) Loch ness monster or a tree trunk; (b) Flying saucers or clouds? Perceptual Set Other examples of perceptual set. Frank Searle, photo Adams/ Corbis-Sygma Dick Ruhl

14 To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree. Cultural Context Context instilled by culture also alters perception.

15 Perception Revisited Is perception innate or acquired?

16 Human Factors & Misperceptions Understanding human factors enables us to design equipment to prevent disasters. Two-thirds of airline crashes caused by human error are largely due to errors of perception.

The following factor(s) affect our detection of weak signals: a. motivation b. fatigue c. expectations d. all of the above e. b & c but not a 17

With respect to sensation and perception, it is fair to say that : a. experience plays no role b. perception does not appear to involve any inborn perceptual capacities c. humans experience external stimuli as they are with little processing by the brain d. none of the above 18