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Over the summer, a few ScienceBloggers were pondering the question of why students disappear from science courses, never to return.

James Hrynshyn wrote that we’re teaching youngsters the wrong thing. Zuska boldy pointed out the things that many of us think but don’t say out loud. Chad Orzel noted that science is hard and shared his thoughts about why students leave. Stein Sigurdsson, on the other other hand, proposed that students leave because science is not hard enough.

Just this week, ScienceBlogger Mike Dunford provided part of the answer to the disappearing student question, when he asked, “Where should the bar be set?

As Abel Pharmboy described in his post about Bruce Alberts:

It’s the teaching.

On a more kindly note, I think there are multiple factors at play. Perhaps the blame lies with a system that hires professors primarily as researchers (teaching is a punishment!). Perhaps we have been irresponsible in not addressing the lack of training and ignorant attitudes on the part of graduate students who earn their keep by working as instructors. (I for one, have found that it’s unrealistic to expect undergraduates to come equipped with the same motivation and learning skills as a PhD candidate, but maybe that’s just me.)

Here’s Mike’s story:

Mike is teaching Zoology 101 for non-science majors. They did an activity in lab putting little worms in watery or salty solutions and seeing how the worms responded (shriveled up and died or swelled up and popped. Ewww!)

“At that time, several of the students asked me to define “diffusion,” “osmosis,” “hypertonic,” and “hypotonic.” I didn’t define it for them. Instead, I told them that they should look up those definitions and get in touch with me during the week if they were having problems understanding them. I also told them that they might be asked to define some of those words on a quiz that they might have next week.”

Naturally, on the quiz, Mike asked his student to define the terms: osmosis, diffusion, hypertonic, and hypotonic.

“There were two versions of the quiz (I’m teaching two sections) and each version asked for definitions for two of those terms. So far, about 25% of the class has managed to define one correctly, and about 10% of the class defined both.

Mike asks:

“Was I unreasonable to make them look up the definitions for themselves? I thought doing it that way, particularly after being told there might be a quiz, would increase their chances of remembering the definitions. Or was it just unreasonable to expect that they would actually do the homework?”

My answer:

You have data. The test scores say you need another approach.

If a large number of students were capable of looking up the definitions and understanding them, would there be any point in hiring an instructor? Do you see your role as an instructor and guide, or as a judge?

Here are the problems that I see with the approach that you took:

1. The definitions that the students find might not be correct.

My oldest daughter is taking AP biology in high school and studying those exact same concepts. She brought home some photocopies of written information that came from a laboratory kit supplied by Wards. After reading through the information, on her own, and looking for the definitions of water potential, osmosis, hypertonic, hypotonic, etc. she came to me, completely puzzled. I read through the materials and found that they contained two definitions for water potential that conflicted with each other.

How are students supposed to understand concepts if they find conflicting definitions in a reading assignment? I could help my daughter because I know these concepts and I’ve taught them. Who was there to help your students realize if a definition was right or wrong?

2. The terms hypertonic, isotonic, and hypotonic, are tricky for students because you need to be really clear about which side of a membrane you’re discussing.

If you have a membrane that’s separating liquids with two different concentrations of solutes, until the equilibrium is reached, one side is hypertonic (relative to the other) and the other side is hypotonic (relative to the other). Students have to know which side is tied to which term or they get very confused.

3. Even though it may appear to you that the definitions the students find are straightforward and correct, it turns out that students don’t always interpret the words (or understand) the words in the same way that you do. Maybe the students did read the definitions but their interpretation of the definitions was wrong.

You mentioned that they could come by and get in touch with you if they were having problems understanding the definitions. It’s been my experience that the students often don’t know when they’re having problems understanding a definition until after they get the test back.

I was taken by surprise once to learn that one of my students was systematically making mistakes because he didn’t understand the word “prior.” I only found this out after several months, and even then, it was completely by accident.

Of course he should have looked up the definition on his own. But he didn’t. He was a nineteen year-old student and not an experienced learner.

4. You also may have written the test in such way that the students didn’t understand the question.

Did you validate the test? That is, did you give the test to anyone else in your lab and have them take it?

My teaching philosophy is that instructors are hired both to help students learn and to help students learn how to learn. When a large number of students have problems, as you saw in your test results, we need to diagnose where and why the problems occured and determine how to solve them.

I would have worked with the students to help them come up with definitions of the terms and used some kind of in-class assessment to determine if the student-derived definitions were, in fact, correct. And I would have used that moment to correct any misconceptions.

If college professors were hired with teaching as their primary mission, rather than a secondary activity, I think we would see a difference in our ability to retain students and maintain their interest in science. As long as we continue to assume that anyone who can get into graduate school instinctively knows how to teach, we will continue to see students drain from the pipeline.

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  1. #1 Mike Dunford
    September 27, 2006

    I’ve posted a reply to the reply here

  2. #2 Alexa
    September 27, 2006

    In Europe, many student surveys are showing that students drop out of science because it’s too hard, and too abstract. There’s a concerted effort going on to make sciences more hands on, and less about book reading. Another criticism which is regularly heard is that the curriculum is overloaded with content. Rather than teaching ‘facts and figures’ we should be teaching the scientific approach: i.e. hypothesising, then designing an experimental methodology to test the hypothesis. This implies that students should be encouraged to design their own experiments as much as possible, rather than to use ‘off the shelf’ methodologies. This improves motivation, as students don’t feel that they are doing an activity which is already ‘answered’ in the text book.

    Finally, I think ethical considerations and sensitivity need to be borne in mind. The experiment described above involves essentially killing small animals to prove/disprove a hypothesis. Many children will be put off science by such a methodology, especially as they already have a negative image of the ‘mad scientist’ doing unethical experiments from the media. It’s important to show children with such concerns that ethics and science can be combined, and that science also involves conservation and respect for other living beings.

  3. #3 Sandra Porter
    September 28, 2006


    You’ve made some interesting points. I will address the first paragraph’s topic in a later post. As for the second point, I’m not sure if college students are too bothered by the ethical issues of killing nematodes. If you saw one crawl out of your salad, you’d probably squish it without hesitating.

    Still, I agree, it doesn’t really seem necessary to use a living creature for this kind of demonstration. In fact, this is the first time that I’ve ever heard of any one using nematodes (the little worms) to illustrate the effects of salt concentration on a cell.

    I always used more mundane items like dialysis bags with different concentrations of salt and food coloring, in beakers of with different concentrations of salt, water, or sugar, to illustrate the concepts of hypertonic, hypotonic, and isotonic solutions. In the biotech lab, we covered this topic in the context of tissue culture – or when we dialyzed protein solutions to remove salts.

  4. #4 Melissa
    October 5, 2006

    I see good points on both sides of this argument, but one comment in particular troubles me:

    “He was a nineteen year-old student and not an experienced learner.”

    What does this reveal about the education of young people before they reach nineteen years of age?? Nothing surprising, I’m sure, but sad nonetheless.

  5. #5 Sandra Porter
    October 5, 2006

    It is sad. I think there is often a misalignment between the skills that college instructors expect students to have, coming in to college, and the skills that they actually do have when they leave high school.

    In this case, I was trying to make the point that it’s not fair to expect a freshman college student to have learning skills that are equivalent to those of their graduate student instructor. A nineteen year student is an inexperienced learner relative to a 25-30 yr old graduate student.

  6. #6 Roy
    January 1, 2007

    When I took chemistry we had to memorize the definitions of molality, molarity, and normality.

    It wasn’t until years after my formal education ended that I discovered these concepts are tools for solving problems. Had we been presented with problems to be solved, then steered toward devising these concepts for ourselves, we would have seen them as prizes we’d earned, not burdens foisted on us.

    My math education was similar. The formal was dreary. Later, I explored calculus and found it a powerful toolkit to solve real problems at home and at work.

    Look at the trouble public school teachers have introducing modular arithmetic. Yet their students have been using modular arithmetic for years already — in reckoning the day of the week and the time of day. A little kid knows that if it’s 2:00 now, then 3 hours earlier it was 11:00. And that if today is Monday then two weeks from today will also be a Monday. The kids may get frustrated trying to explain how they know this stuff so well, but no one doubts they know it.