What is Model-Based Reasoning?

In the dawn of the Next Generation Science Standards (NGSS), the phrase "develop and use a model" is becoming increasingly common. Model-based reasoning is "the ability for students to construct scientific models in order to explain observed phenomena" (from MUSE). Many educators see the word "model" and think of some type of physical model (for example a model of a cell), however, this is a common misconception. Instead, think of a model as "a scientific model is an idea or set of ideas that explains what causes a particular phenomenon in nature" (from MUSE). Major advantages of model-based reasoning include a deeper student understanding of the content, as well as increased student engagement.

To help illustrate this point, examine the flowchart above (click to enlarge), which shows how modeling can be used to teach evolution. The students make a series of observations that lead to inferences, which help to answer a driving question for the unit. (A sample driving question for this unit could be "How do organisms change over time.") Each observation represents a lesson that can be taught in about one class period. An excellent resource for educators who wish to learn more about how to create a modeling curriculum is the Modeling for Understanding in Scientific Education (MUSE) homepage. The curriculum on the website was developed by a team of educators, university researchers, and students, and includes a vast amount of materials. On this website one can view two complete unit plans, for both Natural Selection, and Earth-Moon-Sun dynamics). Complete unit plans, lesson plans, and teacher notes are available for both units. 

Our Experience with Model-Based Reasoning Professional Development 

In order to gain understanding of how to implement model-based reasoning in our classes, the Animo Pat Brown science team sought out the expertise of modeling expert Cindy Passmore. Dr. Passmore has a doctorate in science education, and is currently working at UCSD. Scientific modeling is her specialty.   

• Summer of 2011: The entire grant team sponsored a modeling PD open to Green Dot employees, presented by Dr. Passmore. 
• Summer of 2012: Biology and Chemistry teams conducted phone interviews with Dr. Passmore, and worked on developing curriculum.
• Fall of 2012: TIIP team members met with Dr. Passmore to plan and develop curriculum.
• Spring of 2012: TIIP team members met with Dr. Passmore to plan and develop curriculum, as well as classroom observations.  
  

Outcomes of Model-Based Reasoning Professional Development

Due to the professional development that the team received, parts of model-based reasoning were implemented into all three core science classes (physics, biology and chemistry) at our school. In the space below, I will highlight several curriculum changes in each subject. 

Physics

 9th grade physics students make observations regarding how food coloring spreads in two beakers of water.

The picture above was taken during a 9th grade physics class. The objective of this lesson, which takes place during the thermodynamics unit, is for students to realize that particles with a higher temperature have more kinetic energy than particles with a lower temperature. Before giving the students any content knowledge on the subject, students are asked to make observations when food coloring is placed in a container with low-temperature water, and when food coloring is placed in a container with high-temperature water. Students then discuss their observations and try to come with a "model", that fully explains their observations. 

Biology

Model-based reasoning was implemented in the biology curriculum several times throughout the year. One notable lesson was the "Who is the daddy?" unit. This unit taught punnet squares with the driving question "Who's the Baby's Daddy?" Students were shown seven possible fathers (along with several statistics about each possible father including widow's peak, blood type, etc...), and asked to figure out who the daddy was. View the PowerPoint Here. The picture below shows posters of the seven possible fathers, and the post-its represent each student's initial guess.  

The wall in a biology class, after one period's students made their initial guesses about who the baby's daddy was.

Above is a sample powerpoint slide from the introductory day of the unit.  Students were given information about all seven possible fathers, the mother, and the baby.

Each lesson students were given some knowledge to help them eliminate one father. For example, widow's peak is a simple dominant/recessive trait, and was the first punnet square taught. Students then used this worksheet to eliminate a father based on widow's peak. As students increased their knowledge of punnet squares (incomplete dominance, co-dominance, sex-linked traits), they were able to eliminate more fathers. Essentially, the students were creating a model to discover who the father is.  

To conclude the unit, students completed a writing assignment that explained how they were able to eliminate each father, which required students to reference all the knowledge they had learned throughout the entire unit. This type of cumulative end-of-unit assignment is common when teaching a modeling curriculum. These types of assignments require a student to make sense of everything they've learned, and the assignment usually requires a much deeper understanding than a multiple choice assessment (which are also present in a model-based reasoning classroom).

  

Physics students work on a concept map towards the end of a unit.  When done thoughtfully and correctly, teaching a modeling curriculum encourages students to ask questions, make observations and inferences, and argue their ideas with their peers, which in general also leads to student engagement. Additionally, model-based reasoning requires a deeper understanding of the content.  

Chemistry

Normally, atomic structure is taught through direct instruction. Teachers lecture students on subatomic particles (protons, neutrons, and electrons) and discuss how they fit together to form the atom. In a model-based approach, students are presented with various ideas ("models") for how the atomic might be structured, as shown in the document below (click to enlarge).

Students then read about major experiments in the history of science that were used to elucidate the structure of the atom. After significant discussion about each experiment, students return to the four models above to eliminate any models not consistent with the data. After working through four major experiments, students are able to justify why the proton/neutron model is the currently accepted scientific model of the atom. This lesson concludes with students writing a persuasive paragraph using evidence from historical experiments for the currently accepted model of the atom.

Approaching instruction in this way gives students a much deeper understanding of the content, and touches on important ideas regarding scientific progress over time and the relationship between evidence and ideas.