1. How your mind understands sensory information
Perception
How your mind understands sensory information

2. Sensation vs. Perception
Sensation – to construct the outside world inside our heads we must detect physical energy from the environment and then encode it as neural signals.
Bottom-up processing—Data-driven where sensory information travels from receptors to the brain.
assembling a jig-saw puzzle without the picture
Perception - The process of integrating, organizing, and interpreting sensory information
Top-down processing— Draw upon our knowledge, experiences & expectations to arrive at meaning. Also called conceptually driven processing.
using the picture to assemble the jig-saw puzzle
Sensation and Perception blend into one continuous process, progressing upward from specialized detector cells and downward from our assumptions.

3. Selective Attention
At any moment we focus our awareness on only a limited aspect of all that we are capable of experiencing.
Cocktail party effect – the ability to attend selectively to only one voice among many.
True for visual attentiveness – Neisser study with woman & umbrella - Examples of Change Blindness.
True for auditory attentiveness – Wilson experiment where person listens to two separate conversations (one in each ear). Can only listen to one at a time.
Unattended stimuli can have subtle effects. If someone says your name at a party, your perceptual system may bring that voice to consciousness.
We are constantly filtering sensory info and inferring perceptions in ways that make sense to us.
Look at Necker Cube on oncoming slide – because attention is selective, you can see only one interpretation at a time.

4. Organizational Principles
To transform sensory information into meaningful perceptions our perceptual processes help us organize info so we can answer 3 questions: 1. What is it? 2. How far away is it? 3. Where is it going?

5. Gestalt
Founded by Max Wertheimer, it emphasizes that we view things as a unified whole or figure rather than in isolated bits and pieces
Given a cluster of sensations, the human mind organizes them into a Gestalt
Gestalt psychologists stressed that the whole is greater than the sum of its parts.
By breaking experiences into their basic parts, something important is lost.

6. A Gestalt Figure & Selective Attention What do you see: circles with white lines, or a cube?
If you stare at the cube, you may notice that it reverses location, moving the tiny X in the center from the front edge to the back. At times the cube may seem to float in front of the page, with circles behind it; other times the circles may become holes in the page through which the cube appears, as though it were floating behind the page. Because attention is selective, you see only one interpretation at a time.
For an online demo click below: Necker Cube

7. Temple or Tunnel?

8. What is It? Perception of Shape
We primarily rely on shape to identify things in our environment.
Dax Experiment showed this in 3-year-olds. As long as the object had the same shape as the original dax, the children identified it as a dax.

9. How Far Away Is It? Figure-Ground Relationships

10. Pictures have reversible
Figure and Ground
Gestalt Psychologists also thought that an important part of our perception was the organization of a scene in to its:
Figure—the object of interest
Ground —the background
Pictures have reversible
figure-ground
Different neurons in the brain fire for shapes that are figure than do for shapes that are ground.
Discovering PSY p Figure 3.12

11. Another Figure-Ground Example Do you see musicians or old people?

12. What’s the figure in this picture? Having trouble? Click HERE

13. Illusions The Café Wall Illusion
An object’s background can change and make us perceive things that are not really present.
Click on the video clip below. Are the lines slanted or straight?
The Café Wall Illusion

14. Zollner Effect
Are these squares straight? Straight lines appear to bend if they intersect with or are seen against a background of curved lines. Your eyes and brain are working together to try to make the straight lines fit the background pattern.

15. Spiral Square Case
Are these squares bent? The curves of the spiral in the background make the square seem bent. Ground has a role in how we perceive the figure.

16. Are the letters tilted?

17. Organizational Principles: Grouping Principles

18. Law of Pragnanz (Simplicity)
When several perceptual organizations are possible, the simplest and most stable shape will be perceived
What do you see?
You probably perceived this image as that of three overlapping squares rather than as two six-sided objects and one four-sided object.

19. Grouping Organizing the figure information into meaningful forms.
The perceptual tendency to organize stimuli into understandable groups
Several principles of grouping include:
Similarity
Proximity
Closure
Continuity (Good Continuation)

20. Grouping - Similarity
The tendency to place items that look similar into a group

21. We perceive objects of similar size, shape, or color as a unit or a figure

23. Grouping - Proximity
The tendency to place objects that are physically close to each other in a group

24. Our tendency perceive objects that are close to one another as a unit or a figure. We see three sets of two lines & two groups of three people.

25. Grouping – Closure
The tendency to look at the whole by filling in gaps in a perceptual field

26. Our tendency to fill in the gaps or contours in an incomplete image.

27. Grouping – Continuity
The tendency to perceive that movement of an object continues once it appears to move in a particular direction

28. Our tendency to group elements that appear to follow in the same direction as a single unit or figure. Seeing the line as continuous and the curves as continuous.

30. Shape Constancy