Feedback loops are a physiology professor’s bread and butter. From blood sugar to body temperature, negative feedback ensures that no physiological variable strays from its set point (or range) and that homeostasis is maintained. Positive feedback loops, on the other hand, are inherently unstable. In these loops, the response elicited by a stimulus drives the variable further from its set point, reinforcing the stimulus rather than reducing it, and continuing until some outside influence intervenes1. The classic physiological example of positive feedback is childbirth – pressure from the baby on the mother’s uterus and cervix triggers the release of the hormone oxytocin, which triggers uterine muscle contractions that further push the baby toward the cervix. This loop of pressure, oxytocin release, and contractions continues until an intervening event occurs – the delivery of the baby.
While physiological positive feedback loops are fascinating, they are greatly outnumbered by negative feedback loops; thus, they don’t usually get much attention in our physiology classrooms. We usually tell students that the instability of positive feedback loops is what makes them so uncommon. However, I’d like to use my platform here to argue for a larger place for positive feedback loops in not just our physiology courses, but all of our courses.
I mentioned above that positive feedback loops are inherently unstable because they drive variables further from their set points, so you may be thinking, “why would I ever want my classroom to be unstable?” Imagine it this way: in this feedback loop, the stimulus is an idea, concept, or problem posed by the instructor. The response is the student’s own investigation of the stimulus, which hopefully sparks further curiosity in the student about the topic at hand, and drives him or her toward more investigation and questioning. Granted, this system of learning could certainly introduce some instability and uncertainty to the classroom. Once sparked, the instructor does not have control over the student’s curiosity, which may take the student outside of the instructor’s area of expertise. However, I maintain that this instability actually enriches our classroom by giving students the space to think critically.
Why Encourage Positive Feedback Loops?
Though often misattributed (or even misquoted), Oliver Wendell Holmes, Sr. (poet, essayist, physician, and father of US Supreme Court Justice Oliver Wendell Holmes, Jr.) once wrote “Every now and then a man’s mind is stretched by a new idea or sensation, and never shrinks back to its former dimensions.”2 Neuroscience research supports this assertion. In rodents, exposure to novel stimuli in enriched environments enhances neuronal long-term potentiation, the cellular correlate of learning and memory in the brain3. Human brains both functionally and structurally reorganize upon learning new information. A magnetic resonance imaging study examined gray matter volume in the brains of German medical students who were studying for their “Physikum,” an extensive exam covering biology, chemistry, biochemistry, physics, human anatomy, and physiology4. Brain scans taken 1-2 days after the Physikum demonstrated significantly increased gray matter volume in the parietal cortex and hippocampus compared to baseline scans taken 3 months prior to the exam (and prior to extensive exposure to new information during the study period)4. Thus, while the brain may not literally be “stretched” by new ideas, as Holmes proposed, the process of learning (acquisition, encoding, and retrieval of new information) certainly reshapes the brain.
In the model I’ve presented above, new ideas, concepts, and questions are the stimuli in our positive feedback loop. These stimuli promote changes in our student’s brains. And, if these stimuli spark curiosity, these brain changes (and thus learning) will be amplified as students respond – meaning, as they construct new ideas, concepts, and questions based on their own interests. Thus, the loop feeds into itself.
Designing Stimuli That Elicit Positive Feedback
How can we structure our teaching so that the stimulus we present to our students is strong enough to elicit a response? First, it is crucial that our stimuli elicit curiosity in our students. In his essay surveying recent research on the role of curiosity in academic success, David Barry Kaufman wrote, “Stimulating classroom activities are those that offer novelty, surprise, and complexity, allowing greater autonomy and student choice; they also encourage students to ask questions, question assumptions, and achieve mastery through revision rather than judgment-day-style testing.”5 Project-based learning, a teaching technique focused on extended engagement with a problem or task as a means of constructing knowledge, checks many of Kaufman’s boxes6. As an example, in the past two iterations of my Physiology course, my students have participated in the “Superhero Physiology Project” in which they develop interactive lesson plans for middle school students. Based on the work of E. Paul Zehr, Ph.D. (author of Becoming Batman: The Possibility of Superhero7 and multiple APS Advances in Physiology Education articles), my students choose a superhero to base their lesson upon, and work over the course of several weeks to create interactive, hands-on activities to teach kids about a physiological system. While I give my students feedback on the plausibility of their ideas (within our time and budgetary constraints), I leave much of the structure of their lessons open so that they have the opportunity to work through the complexities that come with keeping 20 or more middle schoolers engaged. Often, my students tell me that figuring out the best way to communicate physiological concepts for a young audience encouraged them to go beyond our textbook to search for new analogies and real-life examples of physiology to which middle schoolers could relate.
Another way to design stimuli that elicit curiosity and positive feedback learning is by capitalizing on a student’s naiveté. In this approach, described by education expert Kimberly Van Orman of the University of Albany in The Chronicle of Higher Education8, “students don’t need to know everything before they can do anything” – meaning, curiosity is most easily sparked when possibilities aren’t limited by your existing knowledge, because you don’t have any! For me, this approach is somewhat difficult. Like all instructors, I regularly feel the pressure to ensure we “get through the material” and often plow through concepts too quickly. However, my physiology students last fall showed me the power of the “naïve task” firsthand when I observed the Superhero Physiology lesson9 they gave at the middle school. They decided that before teaching the middle schoolers any physiological terms or concepts didactically, they would present them with a hands-on experiment to introduce the concepts of stroke volume and vasoconstriction. Their rationale and approach (below) illustrate their mastery of using naiveté to spark curiosity.
The students should be provided with very little, if any, background information on the heart models and the reasoning behind the varying sizes of the materials. By providing little information up front, we hope to intrigue their curiosity regarding the lesson and its significance. Students will be told what to do with the instruments; however, they will not receive any advice on which instruments to use.
- Divide the class into two groups (within each group there should be 4-5 “holders” for the tubes and 4-5 “pumpers” managing water and pipets). Group 1 will be given large diameter tubing, a large funnel as well as 3 large volume pipettes. Group 2 will receive smaller tubing, a smaller funnel and only one smaller volume pipet.
- Instruct the students that they will be transporting the water from a large bucket into another bucket 8-10 feet across the room without moving the bucket.
- The groups will have 10 minutes to construct their apparatus, and 5 minutes for the actual head-to-head “race” in which the winner is determined by who moves the most amount of water in the allotted time.
- After the students have completed the first experiment they will return to their seats for the lecture portion of the lesson which will connect the different parts of the build to different portions of the cardiovascular system.
Not only did the middle school students have a fantastic time building their apparatus (and accidentally on purpose getting each other wet!), but as the experiment progressed, they began to get curious about why the other team was so behind or ahead. Soon after, discussions between groups about tubing diameter and pipet size emerged organically among the middle schoolers, and they were able to easily apply these concepts to later discussions of blood flow and cardiac output.
While I think most educators aspire to elicit positive feedback learning in their students, there can be barriers to putting it into practice. As I mentioned above, pressure to cover content results in some of us shying away from open-ended activities and projects. Not all students in a given class will come in with the same motivations for learning (as discussed in Dr. Ryan Downey’s December 2018 PECOP Blog post10), nor will they all respond to the same stimuli with curiosity. However, it just takes one stimulus to put a positive feedback loop into action – and once it gets going, it’s hard to stop. Once a student’s curiosity is piqued, the classroom may feel a bit unstable as their interests move out of the realm of your expertise as an instructor. But ultimately, we all as educators live for that moment when a connection crystallizes in a student’s mind and they discover a new question they can’t wait to answer.
The author is grateful to Wabash students James Eaton, Sam Hayes, Cheng Ge, and Hunter Jones for sharing an excerpt of their middle school lesson.
1 Silverthorn DU. (2013). Human physiology, an integrated approach (6th Ed.). Pearson.
2 Holmes OW. (1858). The autocrat of the breakfast-table. Boston: Phillips, Sampson and Company.
3 Hullinger R, O’Riordan K, Burger C. (2015). Environmental enrichment improves learning and memory and long-term potentiation in young adult rats through a mechanism requiring mGluR5 signaling and sustained activation of p70s6k. Neurobiol Learn Mem 125:126-34.
4 Draganski B, Gaser C, Kempermann G, Kuhn HG, Winkler J, Büchel C, May A. (2006). Temporal and spatial dynamics of brain structure changes during extensive learning. J Neurosci 26(23):6314-17.
5 Kaufman,SB. (2017, July 24). Schools are missing what matters about learning. The Atlantic. Retrieved from https://www.theatlantic.com/education/archive/2017/07/the-underrated-gift-of-curiosity/534573/
6 What is PBL? (n.d.) Retrieved from https://www.pblworks.org/what-is-pbl
7 Zehr, EP. (2008). Becoming Batman: the possibility of a superhero. Baltimore: Johns Hopkins University Press.
8 Supiano, B. (2018, June 7). How one teaching expert activates students’ curiosity. Retrieved from https://www.chronicle.com/article/How-One-Teaching-Expert/243609
9 Eaton J, Hayes S, Ge C, Jones H. (2018). Superhero cardio: the effects of blood vessel diameter, stroke volume, and heart rate on cardiac output. Unpublished work, Wabash College, Crawfordsville, IN.
10 Downey, R. (2018, December 13). Affective teaching and motivational instruction: becoming more effective educators of science. [Blog post]. Retrieved from https://blog.lifescitrc.org/pecop/2018/12/13/affective-teaching-and-motivational-instruction-becoming-more-effective-educators-of-science/