Cindy E. Hmelo-Silver Rutgers University cindy.hmelo-silver@gse.rutgers

1. Conceptual Representations for Learning about Complex Biological Systems:From Expertise to Instruction Cindy E. Hmelo-SilverRutgers Universitycindy.hmelo-silver@gse.rutgers.edu

2. Overview • Understanding complex systems • Structure-Behavior-Function (SBF) as a conceptual representation • Expert-novice differences in complex systems understanding • Conceptual Representations embodied in instruction • Hypermedia • NetLogo • Into the classroom

3. Why Learn about Complex Systems? • Ubiquitous in the world • Human systems • Cities • Ecosystems • Important for understanding many aspects of science • Potential to integrate across disciplines

4. Understanding Complex Systems • Difficult because: • Multiple levels of organization that often depend on local interactions(Wilensky & Resnick, 1999) • Invisible, dynamic phenomena pose barriers to understanding • Conflict with learners’ prior experience(Feltovich et al., 2001) • Indirect causality (Perkins & Grotzer, 2000)

5. Novice Understanding • Focus on the perceptually available structures (Hmelo, Holton, & Kolodner, 2000; Wood-Robinson, 1995; Hmelo-Silver & Pfeffer, 2004) • Favor simple explanations, central control (Jacobson, 2001) • But can conceptual representations provide organizing frameworks for learning about such systems? • Examples: Emergence, Structure-behavior-function

6. Structure-Behavior-Function (SBF) theory • Allows effective reasoning about the functional and causal roles played by structural elements in a system (Goel et al., 1996). • Structures refer to elements of a system • Fish • Filter • Behaviors refer to how the structures of a system achieve their purpose or output • Filters remove waste by trapping large particles, absorbing chemicals, and converting ammonia into harmless chemicals • “Why” Functions refer to why an element exists within a given (designed) system or the output of the system • The filter removes byproducts from the aquarium

7. Studying SBF as a conceptual representation • Expert-novice study • Two domains: • Aquariums • Human respiratory system

8. Respiratory System Interview: 21 Middle school students 20 Pre-service teachers 13 Experts (8 respiratory therapists, 5 pulmonary physicians) Aquarium Interview: 20 Middle School Students 26 Preservice Teachers 9 Experts (5 hobbyists, 4 biologists) Participants

9. Coding and Analysis • Interviews were coded according to SBF coding scheme for the presence or absence of a target concept. • Structure • “There is sand on the bottom” • “The trachea is divided into two parts” • Behavior • “Fish hide between the plants” • “The brain sends a signal for the diaphragm to contract downward” • Function • “A filter filters out organic waste” • “Lungs bring air into your body…”

10. Results: Respiratory System

11. Sample Responses: What do the lungs do? • Expert: The lungs, pretty much are the place of oxygen gas exchange. It’s where oxygen comes into the body. It’s where acid load by carbon dioxide is released from the body. That’s its primary function….The tissue lungs…well you have…ACE-inhibitor break down…you have…you also have I think insulin break down. Also that occurs in the lungs too. You have oxygen exchange. That’s primary purpose…lungs are oxygen exchange, well oxygen gas exchange. I’m sorry let me get that correct, gas exchange because you don’t want to leave the carbon dioxide out, which is just as important, and its also a mechanism for managing acidosis, pH balance, because its one of the most quick, it’s the most rapid management. You can blow off CO2 even if the CO2 is normal to maintain a decent pH, so its one of the quick modes of balance, pH balance. • Pre Service Teacher: The lungs transfer air, transfer oxygen and carbon dioxide I believe back and forth from the blood stream and the air sacs within the lungs in order to provide it to the blood system. • Middle School Student: Well, they ah, its where the air goes like it helps you breathe. I don’t want to say pumping, but it um, something like that.

12. Results: Aquarium Systems

13. Sample responses: What do fish do in an aquarium? • Expert: Hmm. Um, in an aquarium, fish will do many of the same things that they do in their natural life. They’ll forage for food, they will uh, seek mates and attempt to mate. And many times they will successfully reproduce. Um, they eat, they sleep, they burrow for shelter, and they go through a lot of social aggression, interactions, dominance. They establish dominance and attempt to maintain it over other fishes in the tank. Or uh, go in a submissive mode and spend a lot of time hiding from dominant fishes in the tank. …Specifically, you could list a whole bunch of physiological uh, levels of things that fishes do. Like respire, digest, uh grow, um die. • Pre service teacher: They swim around…they…that’s where they live…so that’s like where their whole habitat is, that’s where there whole life is… • Middle School Student: They swim around, cause it’s like, their like, mini-natural habitat. Fish always swim in water, so it’s like a converse size of their habitat.

14. Qualitative Analyses • Expert interviews: • Provided more elaborate responses • Demonstrated a more integrated understanding that cut across the SBF levels. • Novice interviews: • Mentioned numerous structures

15. Expert-Expert Analyses • All have rich understanding, ∆ emphases • Biologists/ Pulmonologists tended to have more global, abstract understanding • Hobbyists/ Respiratory Therapists more local, situated understanding

16. Biologist Model of Filter • Focused on properties of filter as substrate for bacterial growth • Relationship bet pH and filtration • No discussion of nitty-gritty of behavior • Somewhat abstract

17. Hobbyist Model of Filter • Talk about multiple functions of filter • Composition and mechanics • ∆ kinds of materials and their purposes • Connects to other elements of system

18. Pulmonary Physician Modelof Respiratory System • Looks at system from many levels • CNS and control • Feedback loops • External Respiration • Internal Respiration

19. Respiratory Therapist Mental Model • Discuss multiple levels but lungs are central • Focus on functions and behavior that have direct implication for practice

20. Discussion • Visible structures are best understood. • For the experts, behavioral and functional levels are deep principles that organize their knowledge of the system. • Although all experts have deep knowledge, there are interesting differences • Biologists/ Physicians think in global and abstract ways. • Hobbyists/ Respiratory therapists think in local and situated ways. • Raises issue of what are appropriate target models for instruction

21. Implications • The SBF framework may function as a deep principle that maps on to: • expert ways of understanding complex systems • structure of domain. • SBF framework offers a way for learners to look behind the scenes at phenomena that are not readily perceptually available. • Organizing learning around deep principles such as SBF might enable students to understand new complex systems they encounter

22. Conceptual Representations in Hypermedia • Organizing text and graphics based on: • Expert understanding • Deep principles of domain • SBF as conceptual representation • Proof of concept for emphasizing function

23. Function-centered Hypermedia

24. Structure-Centered Hypermedia

25. Comparing Function-centered vs. Structure-centered hypermedia Participants: 52 undergraduates enrolled in Educational Psychology Random assignment to structure- or function- centered condition respiratory system hypermedia Procedure Students worked with hypermedia x 40 min Written post-test on respiratory system understanding Scoring SBF coding scheme for the target concepts. Structure “The trachea is divided into two parts” Behavior “The brain sends a signal for the diaphragm to contract downward” Function “Lungs bring air into your body…”

26. Results: Visible SBF • Visible SBF includes macrolevel phenomena involved with external respiration • Organ level such as airways, brain, diaphragm, heart, lungs, muscles, ribs • No significant differences across conditions

27. Invisible SBF • Includes microlevel structures and phenomena related to gas exchange, transport, and internal respiration • e.g. alveoli, blood, capillaries, cellular respiration, red blood cells • Rarely mentioned by novices in baseline study

28. RepTools Aquarium Tools

29. Function-centered Aquarium Hypermedia System

32. Simulations and Modeling • Allow learners to experience complex systems phenomena • Simulations and models help focus learners on function and behavior • Make invisible phenomena visible and open for inspection • NetLogo as platform for model development (Wilensky, 1999) • Agent-based modeling tool • High-threshold, low ceiling • Allow understanding of how local interactions contribute to system behavior

33. NetLogo Aquarium Model

34. Nitrification model

35. In the Classroom • Providing scaffolding and sequencing that help establish “why” questions • Mix of hands-on activities, hypermedia resources, simulations, class discussions • Scaffolding needs to encourage mapping: • Between real world and virtual world • Between different levels • Considering how models simplify the world

36. Research Context • Goal to support middle school science instruction in domain of aquarium ecosystem • Units developed with two collaborating teachers • 145 middle school students in 2 public schools for about 2 weeks • 70 7th grade with Teacher A • 75 8th grade with Teacher B • Both classrooms had physical aquaria and 1-2 laptops for each small group

37. Teaching Contexts • Both teachers experienced, considered experts • Teacher A • Used worksheets with open-ended questions • Expected homogeneous progress for whole class • Focus on content • Teacher B • Inquiry-oriented norms for classroom • Scaffolded exploration by asking students to observe and explain, open-ended questioning

38. Research Design • Pre and post tests of SBF knowledge (Hmelo et al, 2007) • Comparisons among classroom • Qualitative analysis of enactments using Interaction Analysis (Jordan & Henderson, 1995)

39. Learning Outcomes

40. Enactments • Although both teachers showed significant gains, IA showed great differences in enactment • Two areas • Creating opportunities for inquiry • Interpretation of computer models

41. Creating Opportunities for Inquiry:Teacher A: Adoption of Student Language • Concentration on definitions of terms • Posed questions requiring one-word response to class as whole • Questions aimed at reproducing declarative knowledge • Adoption of student language to convey behavior of structures • Results suggest student understanding was scaffolded by connecting to prior knowledge as a way to explain new concepts

42. Adopting Student Language • Teacher A: First of all you understand that certain things are living and certain things aren’t. Right? Is ammonia a living creature? • Class: No! • Teacher A: It doesn’t grow, it doesn’t reproduce, it doesn’t respond. How do I get more ammonia in the tank? • Class: Pee • Teacher A: Pee. It’s not like its reproducing and making more. You want more. You want more, you get more fish and more fish do what? • Class: Pee!

43. Creating Opportunities for InquiryTeacher B: Scientific Terminology and Inquiry Orientation • Open-ended questions requiring explanations • Promoted argumentation in student discourse • Incorporation of new scientific terminology

44. Scientific Terminology and Process Inquiry • Alexis: What would happen [if there were no fish]? • Courtney: Well first of all, uh, snails wouldn’t have anything to eat. • Ron: We’re not talking about snails. • Alexis: We’re talking about fish. • Courtney: But they need to have… they wouldn’t make the water dirty. So then the fish wouldn’t have… • Ron: Alright, so they wouldn’t produce waste. We’re not talking about the snails. • Alexis: I just think that there would be no point. What are we going to have a plant farm in water? • Courtney; Basically, nothing would be able to work because the bacteria… • Jenn: Everything lives on fish. • Courtney: The fish produce ammonia, which bacteria makes less harmful and snails keep the water clean by cleaning the waste and the algae. • Ron: OK, so fish are the basis of all this… ecosystem.

45. Interpretation of Computer Models:Teacher A: Technology for Instruction • NetLogo as a teaching aid • Reinforce content knowledge • Concern with student understanding of computer model as end in itself • Homogeneous understanding

46. Technology Use to Provide Instruction Teacher A: Let’s go over the key. Did you figure out what this is? Class: Yeah. Teacher A: What is it? Class: Plants. Teacher A: Brilliant, that’s a plant, you got that one. [Writes it on board] Did you get the red dots? Class: Yeah. Teacher A: What’s that? Class: Ammonia. Teacher A: Very good. OK now I’m going to make it a little harder. White dots? Class: Nitrite. Teacher A: Because what appeared first? Class: Ammonia. Teacher A: Red dots. And what appeared second? Class: White dots.

47. Interpretation of Computer Models:Teacher B: Technology as a Cognitive Tool • Technology as cognitive tool • Affords inquiry • Science as a model building activity • Groups notice different aspects of model • Stimulate cognitive engagement • Use of RepTools to foster deep understanding • Promotion of scientific inquiry • Co-construction of knowledge among group members

48. Technology as a Cognitive Tool Teacher B: …how are you going to know whether the blue boxes are snails, bacteria, what’s the other stuff you said, algae, stuff like that? Courtney: I don’t think it’s bacteria because the red is ammonia and it’s not eating, it’s not getting rid of it. Teacher B: How do you know that? Courtney: Because, um well, you can see the ammonia on top of it and it’s not doing anything to it. Teacher B: Well it’s paused right now. Courtney: Well also because the ammonia is increasing and while these things are increasing too it’s not decreasing the amount of ammonia. Teacher B: It’s not? Courtney: No, well that’s what I observed. Am I wrong? Teacher B: No, no. Ron: Say that again, Courtney… Courtney: I said, I think that the blue can’t be bacteria because bacteria eats ammonia and while the blue is increasing the ammonia is still increasing too so if the blue was bacteria…

49. Discussion • A tale of two classrooms • Different cultures • Different beliefs about learning and inquiry • Appropriation of tools consistent with beliefs • Both teachers • Considered expert • Willing to take risks • Despite differences, similar outcomes • Additional analysis to understand differences

50. Future Directions • Need to better understand learning processes • Fine grained analysis of discourse (Liu, 2008) • Effects of teacher guidance (Marathe, in progress) • More explicit guidance in SBF thinking • ACT (Aquarium Construction Tool) with colleagues at Georgia Institute of Technology