Why are my veins blue?

Common Misconceptions

Watching the video on common misconceptions about the causes of the seasons and the phases of the moon, I was reminded of when I taught Biology 12 this summer and just how challenging it was for students to grasp the mental model I was trying to communicate.  I tried to be creative in how I delivered my lessons by using analogies and manipulatives but still I found many students would erroneously add details or fill in gaps with incorrect information.  Why weren’t they able to acknowledge gaps in their understanding and ask for clarification?  Why did they invent facts?  I don’t believe they were simply too embarrassed to acknowledge their misconception.  Our brains are great at finding patterns and filling in for missed information.  In the image below, it is difficult not to see the unbordered white triangle in the middle.  Our brain fills in what it can’t see.  I feel like this is analogous to how students fill in missing information in order  to complete a mental model of a particular process.  Unfortunately in science, if these assumptions go unchecked, students risk carrying the burden of their false assumptions year after year.  I no longer rely solely on written output to find out what my students understand.  I have long since adopted oral assessments whereby students are asked to explain their understanding of processes fundamental to the unit of study.

In many cases, the students are actually taught misconceptions.  There is mounting research that shows that misconceptions concerning science are prevalent among teachers.  Nancy J. Pelaez et al. (2005) for instance, investigated the prevalence of blood circulation misconception  among prospective elementary teacher in the US and found that “70% of prospective elementary teachers did not understand the dual blood circulation pathway, 33% were confused about blood vessels, 55% had wrong ideas about gas exchange, 19% had trouble with gas transport and utilization, and 20% did not understand lung function”.  I would be curious to see how many of my colleagues would agree that veins in their wrists are blue because they carry deoxygenated blood (deoxygenated blood is still red). My hope is that through greater inquiry based education, teachers will be less required to the absolute bearers of all knowledge and can focus on teaching students the skills required to consolidate, criticize and explain information.


“Kanizsa Triangle.” Optics For Kids – Optical Illusions. N.p., n.d. Web. 10 Jan. 2017.

Pelaez, N. J. “Prevalence of blood circulation misconceptions among prospective elementary teachers.” AJP: Advances in Physiology Education 29.3 (2005): 172-81. Web.


  1. Your point regarding how students can fill in gaps in their understanding using misconceived ideas is a trend I find all too often in my senior math courses. I find that when students do not truly understand a concept, they try to apply previous ideas or their own theories, however inaccurate, to try to make sense of the concepts. Often, this does not work to their advantage, unfortunately. When I have check-in interviews with some of my students and I ask them to explain how they moved from Step A to Step B in their solution, often those who are unsure of the content and/or skills make reference to unrelated concepts (even sometimes from other subject areas) in an attempt to explain their thought process. I find that sometimes this is also fueled by the nature of some of the examples in the textbooks. At times, a textbook will use numbers that are confusing in a context (such as the same integer for both a variable and its coefficient) which can lead students to develop an incorrect understanding. The oral interview is a technique that I find effective to supplement written evaluation, but one that I would like to use more consistently.

  2. Hi Bryn, Do you mind me asking how you orchestrate your oral examinations? It is a great idea, one that I have considered in my own practice, but setting aside the class time seems like a daunting task to me. *** I LOVE LOVE LOVE your connection to the illusion! The concept of our brain’s “filling in what we can not see” is the truth, in so many ways. We are wired to want to understand the ways of the world, and draw conclusions from observing our world, yet those conclusions are often incorrect or at best, partially true. Perhaps, even though we are wired to understand phenomena, perhaps only some of us care enough about certain things to want to be 100% certain with what we think to be true. Countless students are perfectly happy “to get the right answer” without understanding why the answer is what it is. When knowledge is introduced to counter what they believe is true, how many of them care enough to ask the questions and/or dig deeper for the actual truth? (Apathy for KNOWING that something is true, also seems to be a prevalent issue in social media circles, for that matter! It takes too much effort to check for authority these days…) ~Dana

  3. Bryn,

    I think your illusion diagram is a very good analogy of what our brains do in an attempt to fill in the missing links. I think your requirement that students begin to justify and explain their answers is a very good way to ensure that they are not only reaching the correct conclusions, but taking the correct path to get there. It sounds like an excellent learning experience for students to be able to discuss and dissection their own knowledge to see if they can identify any shortcomings in their understanding.

    What I am curious about though is what types of responses would result when students excluded any assumptions or knowledge that they are unsure of. In some ways (and I touched upon this in my own post as well), science itself is filled with knowledge that is generally viewed as incomplete, but is necessary in order to bridge other pieces of knowledge together. For example, Einstein essentially created a cosmological constant in his attempt to produce a calculation prove his belief in a static, non-expanding universe (https://en.wikipedia.org/wiki/Cosmological_constant). Later he concede that was inaccurate but at the time that, it satisfied his views of the universe. So should students use any knowledge they have at their disposal, accurate or otherwise, to connect as many concepts together as possible? Or should they limit themselves to only what has been confirmed by their teachers, and not go beyond?

    Ideally students would have correct and accurate knowledge for each step of their thinking, but are not students by definition in the process of discovering those truths as they learn? Allowing students to express their thinking then quickly identifying their mistakes may be one of the reasons why, as students move higher in the grade levels, they take fewer knowledge risks and instead, as Dana mentioned, simply aim for “getting it right”? To that end, is there a place for misconceptions to be used purposefully as a means to build students towards better understanding? The Bohr model is a wholly inaccurate representation of electron orbital shapes, but does that mean it has no place in guiding students towards understanding spdf orbital shapes?

    This “progressive misconception removal” approach may or may not be a solution, but I do agree, however, that educators should aim to minimize their misconceptions (the blue blood in veins one is something I have to debunk regularly, whether it is science 8 or bio 12!) so that they can ensure that they do not inadvertently add to the misconceptions in students.

    Thanks for the thought provoking post!


  4. Bryn, Great subject header. It certainly invites discussion-so thank you! These are also key questions raised by you: I tried to be creative in how I delivered my lessons by using analogies and manipulatives but still I found many students would erroneously add details or fill in gaps with incorrect information. Why weren’t they able to acknowledge gaps in their understanding and ask for clarification? Why did they invent facts? I like your response using the triangle. This past Fall, I presented a paper at Purdue University called, The Hidden Causal Factor. It is in principle about students’ inventing causal factors to help explain their observations (in this case, they were explaining different boiling points for different substances). It is a highly creative act, and one that the teacher in the study invited. Sometimes they were wrong and did not have the correct terminology, but the teacher provided guidance and evidence to help them think through their invented ideas. As you mention; however, if unchecked, can contribute to an alternative conception that on the surface may appear correct on initial assessment. And what of students? How many students might hold this misconception about deoxygenated blood? Thanks, Samia

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