216 Chapter 6 Sensation and Perception
Psychological and Cultural
influences Lo 6.27
A camera doesn’t care what it “sees.” A digital re-
corder doesn’t ponder what it “hears.” But because
we human beings care about what we see, hear,
taste, smell, and feel, psychological factors can in-
fluence what we perceive and how we perceive it.
Here are a few of these factors:1
Needs and motives. When we need something,
have an interest in it, or want it, we are es-
pecially likely to perceive it. That is why hungry
people are faster than others at seeing words re-
lated to hunger when the words are flashed briefly
on a screen (Radel & Clément-Guillotin, 2012;
Wispé & Drambarean, 1953). People also tend to
perceive objects that they want—a water bottle if
they are thirsty, money they can win in a game, a
personality test with favorable results—as being
physically closer to them than objects they don’t
want or need. Some psychological scientists call
these motivated misperceptions “wishful seeing”
(Balcetis & Dunning, 2010).2
Beliefs. What we hold to be true about the
world can affect our interpretation of am-
biguous sensory signals. Images that remind
people of Jesus or Mary have been reported on
walls, dishes, tortillas, and plates of spaghetti; the
Arabic script for “Allah” has been reported on
fish scales, chicken eggs, and beans. Such images
cause great excitement among those who believe
that divine messages can be found on every-
day objects. However, mundane events inevitablypermitted them to see only vertical lines or
horizontal ones, and nothing else. Later, cats that
were exposed only to vertical lines had trouble
perceiving horizontal ones; they would bump
into horizontal obstacles. Those exposed only
to horizontal lines had trouble perceiving verti-
cal ones; they would run to play with horizontal
bars but not vertical ones (Blakemore & Cooper,
1970).
What about human beings? Because of the
brain’s impressive plasticity (see Chapter 4), some
people who are unable to see until middle child-
hood or even adulthood can regain enough per-
ceptual ability to get along fine in daily life
(Ostrovsky, Andalman, & Sinha, 2006). However,
their perception is unlikely to fully recover. When
adults who have been blind from infancy have
their vision restored, most of them do not see
well. Areas in the brain normally devoted to vision
may have taken on different functions when these
individuals were blind. As a result, their depth
perception may be poor, causing them to trip con-
stantly. They cannot always make sense of what
they see; to identify objects, they may have to
touch or smell them. They may have trouble rec-
ognizing faces and emotional expressions. They
may even lack size constancy and may need to
remind themselves that receding objects are not
shrinking in size (Fine et al., 2003). Generally, the
best recoveries occur when an infant’s congenital
blindness is corrected early, probably because a
critical period for visual development occurs in
infancy or early childhood.
Similar findings apply to hearing. When
adults who were born deaf, or who lost their
hearing before learning to speak, receive co-
chlear implants (devices that stimulate the audi-
tory nerve and allow auditory signals to travel to
the brain), they tend to find sounds confusing.
They are unable to learn to speak normally, and
sometimes they ask to have the implants removed.
But cochlear implants are more successful in
children and in adults who became deaf late in
life (Bouton, 2013; Rauschecker, 1999). Young
children presumably have not yet passed through
the critical period for processing sounds, and
older adults have already had years of auditory
experience.
In sum, our perceptual powers are both in-
born and dependent on experience. Because neu-
rological connections in infants’ brains and sen-
sory systems are not completely formed, their
senses are far less acute than an adult’s. It takes
time and experience for their sensory abilities to
fully develop. But an infant’s world is clearly not
the blooming, buzzing confusion that William
James took it to be.People often see what they want to see. Diana Duyser,
a cook at a Florida casino, took a bite out of a grilled
cheese sandwich and believed she saw the image of the
Virgin Mary in what remained of it. She preserved the
sandwich in plastic for 10 years and then decided to sell
it. An online casino bought it on eBay for $28,000, even
with a bite of it missing!