LAB 7 (CHAPTER 10): OBJECT PERCEPTION
(graded out of 50, worth 5% of final grade)
This lab consists of a two parts, which may be done in the lab or at home. Neither
part requires the assistance of a partner.
Equipment:
No special equipment is needed for this lab, just a copy of this hand-out, and a pencil.
Handing In:
Course website only, no other submission methods accepted. Failure to follow this
instruction properly will lead to a 10% mark deduction.
General Background: In class we discussed how early visual processing ultimately
leads to our ability to perceive and interact with objects. Here we will explore two
facets of this topic. One is multistable figures. These were some of the earliest and
greatest challenges to Wundt's structuralist approach to object perception. The
second concept we will explore is modern structural theories. In particular, we will
examine Biederman's "Recognition By Components" model of object recognition, a
highly influential and contentious theory about how the brain models objects in the
world. Prior to doing this exercise, you should read Chapter 10, esp. section C2.
Part 1: Qualitative Observation of a Multistable Figure
One way that researchers study perceptual phenomena is that they simply observe
them. In the first part of this lab we will practice that method, sometimes referred
to a qualitative observation (a.k.a., phenomenology, naturalistic observation).
Initial Observations: As a first step, take a look at the figure on the preceding page.
Just look at it for a minute or two and record what you see (use objective, scientific
language and include technical terms you’ve learned):
At first the image appear to be black circles with arrows going through them,
then the cube becomes apparent. This is likely due to the occurrence of subjective
contours that was employed to form connections between the white lines in the
black circles. A subjective contour is when the brain produces an impression of an
object in the absence of one.
Some Questions to Consider: Now that you’ve had some time to examine the
figure in an open-ended way, consider the following:
The figure is 2D, but people typically report seeing a cube, which is a 3D structure.
In fact, there are at least 4 versions of a cube that people commonly report. That is,
people typically see the cube either floating in front of eight black circles, or being
seen behind a white wall with eight holes. For either of these interpretations, one
can see the cube as going up and to the right or down and to the left, like so:
This is what is called a “multistable” figure, in that one’s perceptions can stabilize on
one of several interpretations. This is despite the fact that the “sensations” on the
retina remain the same.
Another interesting thing about the figure is that the lines that connect the corners
of the cubes aren’t actually there. They’re only “implied” by the corners, yet people
still perceive them. For some, the lines merely “seem to be there”, while others
report actually seeing faint illusory lines.
Now that you’ve read this over, take another look at the figure on page 1 before
answering the questions below.
Further Observations
1. How many different three-dimensional interpretations of the figure did you see?
I can only see the 3D version of the cube, floating in front of the black circles
and going down to the left.
2. If you saw multiple interpretations, did your perception of them shift back and
forth on its own? Could you make it shift? Were there any tricks you used to make
it shift?
I did not see multiple interpretations despite trying to see it. I tried to focus
on several different points in an attempt to see the cube up and to the right but I was
not successful.
However, I would imagine that it would be possible to make the object shift
between the two orientations once they are both seen.
3. The lines that connect the corners of the cube aren’t actually drawn, but one
perceives them. How strong was your impression of the lines? Did you feel like you
could actually “see” them, or was there merely a “sense that they were there”? Did
the strength of the perception vary depending on whether you saw the cube floating
out front vs. behind?
I did not feel like I could see lines but there was a sense that they were there.
I did not see the cube as floating out from behind, so I am unable to answer the
second part of the question.
4. Please note here any other observation(s) you might have had about the stimulus:
I found my perception of the cube to be very concrete and difficult to change.
5. Did your observations change after you read the background material above?
How? Why?
After reading the background material, I was able to perceive the cube as in
front of the dots as opposed to going through the dots. Once my perception was
changed it was difficult to return to the original point of view.
Instructions for Lab 4, Part 2:
In class we discussed Biederman’s RBC structural description model of object
recognition. In this part of the lab we will look at those models using a naturalistic
observation approach.
Data Gathering
Pick two objects arbitrarily from your environment. These can be anything, natural
or artificial, big or small, animate or not.
1. Sketch out the geon structural description of the two objects below. That is,
sketch out the object as a set of geons such as cubes, cones, spheres, bent cylinders,
etc (see page 346 of the text). Don’t worry, this is not an art class, but do try to keep
things tidy. Label each of the objects and each of its geons.
water bottle
Tupperware
2. How easy or hard was it to break the two objects down into geons? Did this differ
between the two objects? Why?
It was fairly easy to break the objects into their geons as the objects
themselves are relatively simple geometric objects.
3. Do you think the two objects could be differentiated based on their geon
structural description? Could they be recognized from the geons alone? Why or
why not?
I think they cannot be recognized based on their geons alone as the geons are
too general geometric objects and could be perceived as many different objects. This
is likely due to the simplicity of the shapes of the objects I chose.
4. Based on their geons alone, would the two objects both be recognizable from
various angles?
Yes the geons alone would be recognizable from all angles because the
objects themselves appear the same from all angles.
5. Based on your observations here, and your personal experience with object
recognition, what are your thoughts about Biederman’s geon structural description
model?
I think that objects I chose were perfect candidates for Biederman’s geon
structural model because of the simplicity of the object shape. However, I think that
when it comes to more complex objects, Biederman’s model is not applicable. I do
not think that all objects can be made up of only 36 geons as he proposes.