What color do you see?

Generating, collecting, and analyzing data is an essential practice in the science classroom (NRC 2012). Taking this data and using it to craft an explanation that demonstrates understanding of content is another essential practice. But both practices can be challenging, and students often require teacher support to succeed.

Accordingly, we set out to develop a range of activities that would engage students in these practices more meaningfully. We did it as part of Project NEURON—a program that brings together education and neuroscience faculty and graduate students to create high school science curriculum.

One of the activities we created—a color-sorting activity—draws on the principles of visual neuroscience and optics to demonstrate the influence of light and environment on perception and behavior. The activity allows students to collect data, use math and computational thinking, construct explanations, and engage in argument from evidence, as described in A Framework for K–12 Science Education (NRC 2012).

This article describes the color-sorting activity in detail and suggests how teachers can adapt it for their classrooms.

Sorting colored candies

In this activity, students sort colored candies—such as M&Ms—under different-color lights and record data about their speed and accuracy under these varying conditions. This allows them to develop a hypothesis, collect and interpret data, and use that data to support a claim about a core science concept. This simple central experiment provides a foundation for students to develop their own hypotheses and create a plan to test their predictions. The data collected provides multiple levels for analysis, and students use it to articulate their conclusions to a central driving question: “What color do you see?”

This activity balances physics and biology, demonstrating how core physical science principles of light (e.g., color and wavelength) interact with biological structures (e.g., the eye and the brain) to determine behavior (e.g., how quickly and accurately students can sort the colored candies).

The color-sorting activity has been used in a range of science classes, including general and advanced biology, environmental science, and physics. It can be used to discuss adaptation and the interaction between behavior and environment. Students discover they can easily sort colors in white light—the normal environment for humans—and less easily in other “environments.” But they also learn they can improve their speed and accuracy over time.

This activity helps students understand how vision has evolved to give species advantages within their niche: For example, humans distinguish colors in white light. Other species may have different means of sensing the world around them and different ranges of vision, depending on their environment.

Application in the classroom

The color-sorting activity addresses science content standards and engages students in essential scientific practices. Specifically, students

• evaluate how the visual environment affects their own visual perception,

• build familiarity with essential concepts in optics (e.g., the visual spectrum, wavelength, frequency, intensity, absorbance, and transmittance),

• demonstrate the ability to accurately record data in a table,

• analyze raw data by calculating percent accuracy and averages, and

• present data in a graph.

In carrying out this activity, students move through four stations where they sort colored candies under different colors of light: white, red, green, and blue (Figure 1). Colored candy may be replaced by translucent circular tiles or small plastic disks that include red, green, blue, and yellow. (Safety note: If candy is used, have students recall basic lab safety and not eat in the lab.)

FIGURE 1. Students sort candy and collect data under green light.

At each station, students pour a cup of colored candies onto the plate and then attempt to remove all the red ones as quickly as possible while another student keeps time. After the student says he or she has found all the red candies, accuracy is checked under white lights (e.g., how many red candies did he or she miss, and how many did he or she mistakenly identify as red) (Figure 2, p. 64). Students then record their time and accuracy on a data table (Figure 3, p. 64).

FIGURE 2. Procedure in brief.

FIGURE 3. Student data-collection table.

How we perceive color

Our ability to perceive color depends on the physical properties of the object and the light environment, the cells of the retina in our eye, and the interpretation of this information by our brains. White light—such as sunlight and many types of indoor lighting—contains all colors of the visible spectrum. As light is reflected or absorbed, the reflected wavelength determines the perceived color (e.g., a red object reflects red frequencies of light and absorbs all other frequencies).

If the light environment has only a limited spectrum—as in the activity described in this article—colored objects appear different (e.g., a red object under blue light will absorb the blue light, but without red light to reflect, the object will appear black).

Specialized cells for vision in the retinas of our eyes sense the reflected light: Rod cells sense light intensity, and cone cells are responsible for color vision. The presence and distribution of retinal cone cells underlie color vision, and differences in these cells cause color blindness, or decreased ability to perceive color differences. After perception in the retina, the light signal is conveyed as a nerve impulse to the brain’s visual centers.

Students take turns sorting candy and recoding data so that all students have a chance to generate their own data. Because multiple students sort the candies, there should be enough cups at each station to allow each student to sort from a different cup; this eliminates preexisting information about how many red candies there are.

Each cup should be uniquely numbered so students can later identify which data came from which cup. Students rotate through the different-color light stations so they can observe how their own speed and accuracy varies depending on the environment and how this compares to the control group (i.e., white light). As a class, students can discuss which conditions were the most challenging and answer the question: “How does environment affect perception?” Students can also predict how the results would change if there were differences not only in the external environment but also in the eye, as in color blindness. Color blindness is relatively common (as much as 7–10% overall, and more common in males [Deeb 2005]), so there may be color-blind students in the classroom.

Students can then compile their class data on a summary data table and use information about average time and accuracy to create a graph (e.g., accuracy in different light conditions or speed in different light environments).

Assessment

To assess student learning, teachers can have students develop a scientific explanation based on the data collected from the color-sorting experiment. This explanation should include a claim, evidence, and reasoning, as described by McNeill and Martin (2011) (Figure 4), or it can be extended to include a rebuttal—illustrating students’ understanding of a complex situation.

FIGURE 4. Claim-evidence-reasoning model (McNeill and Martin 2011).

The addition of a rebuttal to the claim-evidence-reasoning model allows students to evaluate alternative explanations and articulate why their claim is strongest. Further, a two-part graphing and scientific explanation assessment provides support for students using data as part of their explanation while making meaning of the activity. After completing the color-sorting task under different-color lights, students are asked to depict their data in a graph and use that graph to answer the question “How does the environment influence perception?”

To address this question, students create a graph of the classroom data, including the light conditions on the x-axis and the measure (e.g., time, accuracy, or completeness, with units) on the y-axis. Then they develop a scientific explanation using their data as evidence of a claim about the connections between environment and color perception. These explanations are then shared with the class or submitted as a written assignment. Sharing their explanations demonstrates the importance of rebuttal in scientific argument, as students may have varying claims and can then be asked to defend theirs, reconcile different claims into a unified explanation, or revise them based on the discussion.

Teacher feedback

This candy color–sorting lesson is situated in a series of other science activities and experiments that address a central question—“Do you see what I see?”—about vision, light, neuroscience, evolution, and behavior. In this series of lessons we created for Project NEURON, a program funded by the National Institutes of Health Science Education Partnership Award, students explore:

• how environment influences their own perception,

• how environment influences perception and behavior in species in nature, and

• how environment and behavior interact to influence change over time in traits and behavior.

The activity and assessment provided have been used in multiple levels of high school biology, anatomy and physiology, and environmental science classrooms. The color-sorting activity was used with juniors and seniors to demonstrate how environmental factors, such as light, influence organism behavior and how the color of light affects perception. The activity has also been adapted for use in an anatomy classroom to explore the senses and the structure and function of the eye. Teachers who used the activity report that “students were extremely engaged in the data collecting portion of the lesson; they were fascinated by how the colors of light would affect what they did.” In addition to exploring the content learning objectives, this activity also served as a basis for discussion about science practice. Other teachers reported that “[students] were also interested in discussing how learning and bias can creep into experiments.”

We have also seen this activity used in physics classrooms to demonstrate real-world applications of physics. The activity allowed students to more deeply explore the principles of optics. While teaching about light, mirrors, and lenses, one high school physics teacher identified the activity as a means for allowing students to experience how light influences perception: “The physics book [goes] through light perception fairly quickly, so the lesson hits on the importance of it and how we perceive things.”

Conclusion

Teachers often comment on the usefulness of data collection and graphing from this activity. It helps engage students in evidence-based argument. All of the curriculum materials, including complete lesson plans and student handouts for this activity, are available on the Project NEURON website (see “On the web”; Blattner et al. 2012). We hope you will use them to integrate this color-sorting activity into your own science classroom.

Addressing the Framework.

This activity address the following standards listed in A Framework for K–12 Science Education (NRC 2012):

• Physical Sciences disciplinary core ideas

  • PS4.A: Wave Properties
  • PS4.B: Electromagnetic Radiation
• Life Sciences disciplinary core ideas

  • LS1.A: Structure and Function
  • LS1.D: Information Processing