Is Seeing Always Believing?
Lance Pearson
Number of Learners: 90 Students
Date: 05/14/05
Grade (or Age): 8th grade
School/Town: Timilty Middle/Roxbury
Estimated Length of Session: 40-50 minutes
Curriculum Area: Science (Biology)
PREREQUISITE KNOWLEDGE AND SKILLS
None is necessary.
CONTENT TO BE TAUGHT
This lesson plan is aimed at undeniably demonstrating that there can be a
difference between our visual perception (our "mind's eye" view) of the world
and reality itself. It is also aimed at motivating an interest in
scientific explanations of the origins of these problems and how the brain is
involved.
RATIONALE
Fundamental to scientific education is fostering a sense of skepticism about
our own perceptions (or first impressions) and a curiosity about why we make
mistakes and others have differences of opinion. This lesson plan is aimed
at establishing both (a) a skepticism about our own senses or impressions and
(b) a healthy curiosity about how our brains work.
In so doing, it follows up and (obviously) substantially extends for higher
grades the Massachusetts Frameworks Life Science (Biology), Grades K-2
curriculum standard: 6. Recognize that people and other animals interact with
the environment through their senses of sight, hearing, touch, smell and taste.
It also touches upon standard: 6. Identify the general function of the major
systems of the human body (sensation, digestion, respiration, reproduction,
circulation, excretion, protection from disease and movement, control and
coordination) and describe ways that these systems interact with each other.
GOALS
Students will fill out a worksheet documenting their observations of various
visual illusions.
Students will propose their own ways to test whether their perceptions match
reality.
PERFORMANCE OBJECTIVES
Each student will be responsible for recording their perceptual observations
of a still visual illusion slideshow.
Each student will be responsible for designing and/or recording ways to test
whether their observations of the visual illusions are accurate (e.g. use a
meter sick or other straight edge to test for linearity).
MATERIALS
Computer with MS Powerpoint capability
LCD projector for the presentation
Alternatively
The still pictures can be printed out on transparencies and shown on
an overhead. The neon color spreading and retinex theory examples require
color printouts.
PROCEDURE
This lesson plan is fairly light on content, being primarily designed to
strike home an essential point (our sense of sight can fail us in many ways).
A. Opener
Pass out the first worksheet (the worksheets are sequential so you can hand the
second worksheet out now or when you move through the slideshow the second time
if desired).
Students should
answer
the questions on the handout as we move through the slideshow.
Emphasize
thoroughly that there are no right or wrong answers during the first portion of the class... what other
people see or write down is not important. Instruct them to simply answer
honestly what the
pictures look like to them.
The slides are fairly self
explanatory.... One thing to note: in the Checker-Shadow example it should be
emphasized that we are talking about the shade of grey used to paint the blocks
of the picture. We are not interested in what color the blocks would be if there
were no shadow; only in how dark the two blocks look.
B. Development
Hand out the second worksheet (this worksheet is optional).
Students discuss
their answers about their perception of these phenomena and propose ways to
verify their answers. How could we
double-check (verify) whether what you (or anyone else) are seeing is what is
actually there?
Examples:
(1)
Take away the
black blocks in Hermann grid. You can note that in this case (there are no grey
dots in reality), the perception of your eyes when you are focusing on something
is better than the peripheral vision. You can use this to lead into a
discussion of how your fovea is much better at seeing detail then peripheral
vision; just try to read a newspaper using only peripheral vision... (2) Use a meter stick
or other straight edge (or take away the non-vertical lines) to check for linearity
in the Hering Illusion. (3) Use something that can measure right angles (like
the corner of a sheet of paper) to verify the lines are all parallel and
straight up and sown or left to right in the Cafe Wall example. (4) Take
away all the other blocks or have a grey color bar to compare to each of the
blocks in the Checker-Shadow example. (5) Use something to cover or erase the
black lines from the Neon Color Spreading example. (6) Zoom in close (e.g. with
a magnifying glass) to examine the colors in the Retinex example.
Students are
prompted to explore the implications these demonstrations have for the
confidence they should have in their senses.
C. Closing
Summarize the central conclusion that
should now be clear to the students: there
can be a difference between our perceptions and reality. Also emphasize
that we can become aware of these differences (errors) (a) when other people
have different perceptions than ours, (b) when our other senses provide
contradictory information or when (c) our perceptions of other objects provide
inconsistent comparisons.
ACCOMMODATIONS
Establishing a word wall with key words and definitions like Perception and
Reality together with their definitions can be a great assistance to
English-learners.
EVALUATION
The accompanying worksheets provide a baseline measure of attentiveness and
participation. Student
involvement in discussion of the phenomena can also be used for assessment as
well.
EXTENSION
Additional lesson plans in the series present various examples of visual,
auditory and tactile illusions. Students may explore other visual
illusions online or research scientific explanations for particular illusions
they find interesting.
REFERENCES
Search for:
Hermann Grid
Hering Illusion
Cafe Wall Illusion
Checker-Shadow Illusion
Neon Color Spreading
Retinex Color
ASSOCIATED APPENDICES
Appendices for "Is
Seeing Always Believing?" Lesson Plan