1. THE VISUAL SYSTEM: PERCEPTUAL PROCESSES
To see is to believe and to believe is to see: we subjectively interpret sensory input (our perception) based on various factors → experience gives us expectations which give us a perceptual set: a mental predisposition to perceive one thing and not another

5. THE VISUAL SYSTEM: PERCEPTUAL PROCESSES
→ Our perceptual set can influence how we interpret reversible figures

6. The Loch Ness Monster? (or a tree branch)

7. PERCEIVING FORMS, PATTERNS, AND OBJECTS
Besides experience and expectations, perception of form is influenced by selection of sensory input (where do we put our focus?) → selective attention focuses our conscious awareness on specific stimuli, thus causing inattentional blindness: the failure to see visible objects when our attention is elsewhere

8. PERCEIVING FORMS, PATTERNS, AND OBJECTS
→ related to inattentional blindness is change blindness, or the failure to notice changes in the environment

9. PERCEIVING FORMS, PATTERNS, AND OBJECTS
How do we perceive objects/forms? Feature analysis suggests we take specific visual elements – lines, edges, corners – and build them into more complex form → this involves bottom-up processing: from individual elements to the whole or from the sensory receptors to the brain A → /-\ → A

10. PERCEIVING FORMS, PATTERNS, AND OBJECTS
However, to explain form perception we also need to use top-down processing: from the whole to the elements using our expectations and experience → word perception and subjective contours suggest the use of top-down processing

11. PERCEIVING FORMS, PATTERNS, AND OBJECTS
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12. PERCEIVING FORMS, PATTERNS, AND OBJECTS

13. GESTALT PRINCIPLES
Gestalt (German for form/whole/shape) psychology emphasizes our tendency to integrate pieces of information into meaningful wholes so that the ‘whole is greater than the sum of its parts’ → for example, the phi phenomenon refers to the illusion of movement (the whole) using rapidly presented visual stimuli (the part)

15. GESTALT PRINCIPLES
→ Figure and Ground: the organization of visual objects (the figures) that stand out from their surroundings (the ground)

16. GESTALT PRINCIPLES
→ Proximity: grouping nearby objects together

17. GESTALT PRINCIPLES
→ Closure: filling in the gaps to create a complete whole object

18. GESTALT PRINCIPLES
→ Similarity: stimuli that are similar get grouped together

19. GESTALT PRINCIPLES
→ Continuity: we perceive smooth, continuous patterns, not discontinuous ones

20. GESTALT PRINCIPLES

21. GESTALT PRINCIPLES
The concept of perceptual hypotheses suggests we turn these perceptions into a representation of the real world by making inferences about what form might be responsible for what pattern → these hypotheses are formed not only be our perceptual set (expectations), but also by the context

22. DEPTH AND DISTANCE
We make judgments about how far and near things are in space – depth perception – by using various cues → binocular cues depend on the use of two eyes and include: 1. retinal disparity: the brain compares images from each retina to compute distance → the greater the disparity, the closer the object 2. convergence: the sense of the eyes coming together as they focus on closer objects

23. DEPTH AND DISTANCE
→ monocular depth cues are based on the use of either eye alone and include pictorial depth cues given by a flat picture, including: 1. linear perspective: parallel lines appear to meet in the distance 2. texture gradients: texture becomes more dense and less distinct further away

24. DEPTH AND DISTANCE
3. interposition: an object blocking the view of another is closer 4. relative size: similar-sized objects are closer if they appear larger 5. relative height/height in plane: distant objects appear in the upper part of the picture

25. DEPTH AND DISTANCE
6. light and shadow: depth is created by light patterns consistent with our assumption that light comes from above

26. DEPTH AND DISTANCE
* Depth cues and subjectivity: 1) evidence suggests cultures with little exposure to flat pictures miss pictorial depth cues, 2) our motivation can influence our sense of depth – desirable objects may appear closer

27. DEPTH AND DISTANCE
** relative motion: stable objects appear to move as we move – those beyond a fixation point move with us, those in front move backward

28. PERCEPTUAL CONSTANCIES
Our ability to perceive objects as having consistent shapes, sizes, and colors even as illumination and retinal images change is perceptual constancy → color constancy occurs when we perceive objects having constant color even as changing illumination alters the wavelengths reflected by the object

29. VISUAL ILLUSIONS
Once again, our perception of the world is subjective – as visual illusions show, the perceptual hypotheses we form about the world are sometimes wrong → the Muller-Lyer illusion shows the relation between (mis)perceived depth/distance and our perceived size constancy (if we perceive one object as farther away, our brain assumes it’s larger than a closer object)

30. VISUAL ILLUSIONS
→ the ponzo illusion occurs due to the same factors as the Muller-Lyer

31. Zollner Illusion

32. VISUAL ILLUSIONS
→ the Ames room works by removing the perception of different depth: we think the objects are the same distance away

33. VISUAL ILLUSIONS
→ impossible figures occur because we understand the specifics of the picture, but the whole doesn’t make sense (bottom-up processing)

34. VISUAL ILLUSIONS
→ the moon illusion: the moon appears larger near the horizon than it does up in the sky

35. VISUAL ILLUSIONS
* As with monocular cues, we can see cross-cultural differences with visual illusions: people living in a ‘less-carpentered’, straight-lined, right-angled world are less susceptible to the Muller-Lyer illusion and others