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Parallel Processing
TEACH 1.6-8
Enrichment
Tell your students that Anthony
Marcel, of Cambridge University,
Distributed by Bedford, Freeman & Worth Publishers. Not for redistribution.
argues that people with blindsight
have superb vision, but they don’t
know they can see. Employing a high-
speed camera, Marcel tracked the
arms, hands, and fingers of individuals
with blindsight as they reached for
objects they could not consciously
see. The films indicate that their reach
was quite precise. This suggests that
their vision remains intact; only the
neural areas that bring vision into
awareness are impaired.
PRACTICE Copyright © Bedford, Freeman & Worth Publishers.
Research Methods & Design
(SP 2)
(5 minutes) Ask students to explain
why case studies are so limited in
their generalizability. (Intensive case
studies are sometimes very reveal-
ing, and they often suggest direc-
tions for further study. But atypical
individual cases may mislead us.)
03_myersAPpsychology4e_28116_ch01_002_163.indd
132 Unit 1 Biological Bases of Behavior
03_HammerTE4e_47547_ch01_2a_163_4pp.indd 132
ocessing to construct visual per
ceptions?
1.6-8 How does the brain use parallel processing to construct visual perceptions?
1.6-8
How does the brain use parallel pr
Our brain achieves these and other remarkable feats by parallel processing : doing many
things at once. To analyze a visual scene, the brain processes its subdimensions — motion,
form, depth, color — simultaneously.
To recognize a face, your brain integrates information projected by your retinas to sev-
eral visual cortex areas and compares it with stored information, thus enabling your fusi-
form face area to recognize the face: Grandma! Scientists have debated whether this stored
information is contained in a single cell or, as now seems more likely, distributed over a net-
work of cells that build a facial image bit by bit ( Tsao, 2019 ). But some supercells — actually
nicknamed “grandmother cells” — do appear to respond very selectively to 1 or 2 faces in
100 ( Bowers, 2009 ; Quiroga et al., 2013 ). The whole face recognition process involves con-
nections between visual, memory, social, and auditory networks ( Ramot et al., 2019 ). Super-
cells require supersized brain power.
Destroy or disable a neural workstation for a visual subtask, and something peculiar
occurs, as happened to “Mrs. M.” ( Hoffman, 1998 ). After a stroke damaged areas near the
rear of both sides of her brain, she could not perceive motion. People in a room seemed
“suddenly here or there but I [had] not seen them moving.” Pouring tea into a cup was a
®
AP Science Practice challenge because the fluid appeared frozen — she could not perceive it rising in the cup.
Research After a stroke or surgery has damaged their brain’s visual cortex, some people have expe-
“Mrs. M.” is a great example of rienced prosopagnosia (face blindness). Others have experienced blindsight (see Module 1.5a ) .
a case study. Recall that case Shown a series of sticks, they report seeing nothing. Yet when asked to guess whether the sticks
studies are a non-experimental
method. They show us what can are vertical or horizontal, their visual intuition typically offers the correct response. When told,
happen and may offer ideas for “You got them all right,” they are astounded. There is, it seems, a second “mind” — a parallel
further study, but their generaliz-
ability is limited. processing system — operating unseen. These separate visual systems for perceiving and for
acting illustrate once again the astonishing dual processing of our two-track mind.
* * *
Think about the wonders of visual processing. As you read these words, the letters reflect
light rays onto your retina, which triggers a process that sends formless nerve impulses to
several areas of your brain, integrating the information and decoding meaning. The amaz-
parallel processing processing ing result: We have transferred information across time and space, from our minds to yours
( Figure 1.6-16 ). That all of this happens instantly, effortlessly, and continuously is indeed
multiple aspects of a stimulus or awesome. As Roger Sperry (1985) observed, the “insights of science give added, not less-
problem simultaneously.
ened, reasons for awe, respect, and reverence.”
Parallel processing: Recognition:
Retinal processing: Feature detection: Brain cell teams Brain interprets the
Scene cones bipolar cells Brain’s detector cells process combined based on information Tom Walker/Getty Images
constructed image
Receptor rods and
respond to specific
information about
ganglion cells features—edges, lines, color, movement, from stored images—
and angles
form, and depth
it’s a tiger!
Figure 1.6-16
A simplified summary of visual information processing
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