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Blind Spot Activity

Activity Description

“Blinded by Science” is a hands-on activity where students become aware of their blind spot and use this information to make hypotheses about the structure of the visual system.

Students learn that our sensory systems are not perfect and can actually “lie” to us.

This activity is used to begin a unit on sensory systems and the ways in which we can investigate how our nervous systems are structured through observable sensory phenomena.  It is followed by investigations into the auditory and vestibular systems, and then student-designed experiments dealing with an additional sensory system of their choosing.

This activity can be adapted to include discussions about evolutionary biology and the development of vision.


Estimated Time of Activity

The actual blind spot activity is designed to take one class period.  The assignments may be completed in additional classroom time or as homework.  A total of 4 - 6 class periods of time are needed to complete all of the materials.


Activity Objectives

Students will begin to understand the limitations of our sensory systems and how our nervous systems compensate for these limitations.  Students will use experimental observations to formulate hypotheses about the nervous system.


Universal Design for Learing (Differentiation)

This activity is student-guided and inquiry based.  Assessment questions are open-ended with an emphasis on scientific thinking more than actual experimental results.


Activity Prerequisites (Pre-Activity)

Students should be familiar with the basic structure of the retina, including photoreceptors, the optic nerve, and the fovea.

Here is a lecture for the Basic Structure of the Visual System.


Activity Instructions

Day 1:

  1. Start class off with open-ended questions, such as “how do your eyes work?” with the aim of students coming up with their own questions about the visual system.
  2. Write down many of the questions that the students have on the board or on a large piece of paper so that they can be kept up for the duration of this activity.
  3. This can be a short process (say the first 20 minutes of a class period) or more time can be spent on it if available (say two periods).
  4. Finish with a brief presentation about the basic structure of the visual system using the aforementioned slides.
  5. Note that depending on pace, “Day 1” can be up to 3 days (longer is better!).

Day 2:

  1. Students are each given a blind spot tester.
  2. Students are instructed to hold the tester horizontally at an arm’s length away, with the smiley face on the right.
  3. Students are told to cover their right eye, and while looking at the smiley face, slowly bring the piece of paper closer until they notice something happen to the frowning face.
  4. Have students switch eyes and do the same process but while looking at the frowning face.
  5. Have students develop questions about what the brain fills in or leaves out in regards to the blind spot. The homework assignment (below) is designed to foster this process.





            for other types of blind spot testers.

Day 3:

  1. To start off class, have students volunteer some of their answers to the homework questions and encourage group discussion.
  2. The assignment/assessment that student will begin today will have them designing some preliminary experiments to address these questions.
  3. This day can be extended into additional days to allow for more discussion and hypothesis development.

Day 4:

  1. Have students look back at their original questions from day 1, and see if anyone feels that they have gotten closer to answering some of them.
  2. Encourage students to share their results from their assignment and particularly encourage discussion regarding what their results tell us about how the visual system works.
  3. Emphasis should be on what can be ascertained based on their results.


NYS/CCL Standards (Content Knowledge, IAD)

Identify the standards the activity is aligned with.

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To be given during Day 3 and completed as homework:

Students are asked to make their own blind spot tester, to hypothesize how the brain will fill it in, and write up their results.

Activity Sheet



Homework assignment post Day 2 (may also be completed during Day 2 if time allows):

Have students answer these questions in their notebooks

Why does the dot disappear?  How can this be explained by the structure of the retina?

What did you notice about the color of the background and the color of the blind spot?  How might the visual system accomplish this?

What about the pattern of the background?  How might the visual system accomplish this?



1. blind spot testers

2. Diagram of the retina

3. Diagram of the visual system

Instructor’s Notes

The time needed to complete this activity will vary greatly depending on both the level of the students, and the students' familiarity and experience with inquiry-based activities.

Different blind spot testers

More about Blind Spots