128 CHAPTER 3
Figure 3.24 Perceived Motion
Notice anything as you move your eyes over this image? The image is not moving; seeing the circles move
is due at least in part to movements of your eyes.activity in a visual area sensitive to motion. However, this activity was greatest when
accompanied by guided eye movements, suggesting eye movements play a significant
role in the perception of the illusion (Kuriki et al., 2008).
Eye movements have also been found to be a primary cause for the illusory motion
seen in images based on a 1981 painting by Isia Levant, Enigma. Look at the center of
Figure 3.25; notice anything within the green rings? Many people will see the rings start
to “sparkle” or the rings rotating. Why does this occur? By using special eye-tracking
equipment that allowed them to record even the smallest of eye movements, researchers
found that tiny eye movements called microsaccades, discussed earlier in the chapter, are
directly linked to the perception of motion in Enigma and are at least one possible cause
of the illusion (Troncoso et al., 2008).
These two studies highlight some of the advances researchers have made in exam-
ining questions related to visual perception. For more information about the study of
visual illusions as used in magic and the study of such illusions from a neuroscientific
perspective see the Applying Psychology section at the end of the chapter.
OTHER FACTORS THAT INFLUENCE PERCEPTION Human perception of the world is
obviously influenced by things such as culture and misinterpretations of cues. Follow-
ing are other factors that cause people to alter their perceptions.
People often misunderstand what is said to them because they were expecting to
hear something else. People’s tendency to perceive things a certain way because their
previous experiences or expectations influence them is called perceptual set or percep-
tual expectancy. Although expectancies can be useful in interpreting certain stimuli, they
can also lead people down the wrong path. What you see depends upon what you expect
to see. Participate in the experiment Ambiguous Figures to see how perceptual set influ-
ences how you identify various ambiguous figures. Simulate the Experiment, Ambig-
uous FiguresFigure 3.25 “Reinterpretation of
Enigma”
As in Figure 3.24, the motion you see in
this static image is because of movements
of your eyes, this time due more to tiny
movements called microsaccades.
Created by and courtesy of Jorge Otero-Millan,
Martinez-Conde Laboratory, Barrow Neurological
Institute.
perceptual set (perceptual
expectancy)
the tendency to perceive things
a certain way Decause Rrevious
experiences or expectations
influence those RerceRtions.