Chapter 5:
Object Perception
 

The Gestalt Approach to Understanding Perception (pp. 145-156)

  1. Check out this example of a well known visual illusion.  Also, follow the instructions for the demonstration on p. 147.  Why do these two examples pose problems for structuralism?
     

  2. What was the basic idea that the Gestalt guys proposed as an alternative explanation for perception?
     

  3. Pragnanz can be thought of as the "master" Gestalt law...all of the others (similarity, proximity, etc) are sub-laws that explain in more detail how Pragnanz works.  Take a look at these examples and explain how Pragnanz accounts for each:
     

    Write a short sentence or two describing what you see above.  Then click here.

     

  4. Now, do the same analysis for the figures on pp. 149-153.  By the time you are finished, you should have a good understanding of each of the following laws:

    • similarity

    • continuation

    • proximity

    • common fate

    • closure

    • meaningfulness/familiarity
       

  5. In-class activity:  do a web search to find one or more images (hint: use a Google Image search) which illustrate each of the Gestalt laws above.  Submit your URLs to the QuickCheck utility in Connected Learning.
     

  6. What's all this stuff about laws, heuristics and algorithms?
     

  7. The Gestalt laws have a lot of face validity and, as we've seen, it's easy to find examples which seem to illustrate the laws.  But...what kind of empirical evidence is there for these laws?
     

Constructing Objects and Segregating Them From Their Background .  (pp.156-159)

  1. Figure-ground segregation is a prerequisite for the perception of any visual object.  Why?
     

  2. What are some of the factors which influence whether something will be seen as figure or ground?
     

  3. In the vase-face figure (Fig 5.20), it is difficult to see both figures at the same time...instead, they tend to alternate.  Based on Goldstein's comments on p. 159, why is that?
     

Summary Activity

As we have seen, many of the ideas in the preceding sections are not new.  In fact, much of the basic intellectual basis for these concepts was suggested in the mid 1800s by Hermann von Helmholtz (1821 - 1894) .   He called is overall theory of perception "Unbewußte Schlusse", though we can perhaps remember it better as "Unconscious Inference" or "Intelligent Perception".  The model is summarized in contemporary terms by the diagram at the bottom of this web page.  Your task is to review the examples below, most of which come from pp. 145-159, and be ready to argue that they either support or differ from Helmholtz's views.

  • structuralism

  • apparent movement

  • Pragnanz and the other Gestalt laws vs. heuristics

  • the images of the ovals, the pac-men and the dog at the top of this page

  • Fig. 5.20

Feature Integration Theory  (163-168)
 

  1. Anne Treisman's work on Feature Integration Theory (1987) is widely respected and serves as a model for how experimental psychologists study cognitive processes.  First, let's look at the basic model:

    Here is another way to visualize FIT.

    This is all fine, but remember that theories are free for the asking...so, what kind of evidence is there to support her model?   Some observations:

The Preattentive Stage

  1. In a visual search task like Figure 5.34, people are able to find the O among the Vs very quickly, no matter how many Vs there are...the Os seem to "pop out" of the display:
     

    Feature search:

     

  2. On the other hand, finding a lone R among a bunch of Qs and Ps is slow and difficult (Fig 5.35)
     

    Conjunction Search:

     

  3. How has Treisman interpreted these 2 findings?
     
  4. Also, the first two figures on the left are perceptually very different from the third.  What does Treisman make of this?
  5. Remember the illusory conjunction experiment from the last chapter?

    6. 4 AHR 2

    What does Treisman think that this phenomenon tells us regarding FIT?

     

  6. How does the preattentive stage of FIT hold up under what we know about early visual processing in the LGN and V1?

The Focused Attention Stage

  1. Of the two tasks shown below, people find the one on the left to be much easier and quicker to perform.  According to Treisman, why is this?
     
  2. Within FIT, how are focused attention and the binding problem related?
     

Recognition By Components (pp. 168-172)
 

Irving Biederman has been influential in the object perception literature with a theory based around geons.  So, some questions:

  • What are geons and what are their properties?
  • What do geons have to do with perceiving objects?
  • How is this theory different from/similar to Triesman's?

 

Intelligence and Top-Down Processing in Object Perception  (pp. 172-178)

  1. Pages 172-174 discuss several problems faced by our perceptual system.  Take a look at the photo below and be ready to use it to illustrate those problems.
     
  2. What do heuristics and top-down processing have to do with all of this?
     
  3. The model below is a somewhat expanded version of Fig. 5.5.  You should be ready to discuss the procedures and results of the research by Palmer (1975) and Treisman (see Fig. 5.54) and then explain how this work fits into the model.