EDUCATIONAL PSYCHOLOGY

Chapter 7, page 158

Problem 7.10

Understanding students’ thinking: Students’ arguments

Here is an essay written by a sixth grader on the topic of whether research that harms animals

should be illegal. The essay was not to be merely a persuasive essay arguing for one side of the

question. It was supposed to be an essay that explored multiple sides of an issue. Here is one

student’s essay. Evaluate the quality of her essay.

I don’t think that animals should be used in research because it’s not fair to the

animals. Animals have rights too. Even if they’re not just like humans, they are still

living creatures so we have to treat them kindly. How would you feel if someone

wanted to take your pet dog or even your pet hamster and use it for medical research

and how would you feel if the pet died? Even if these animals that are being used in

research aren’t someone’s pets, they should still be treated the same as if they were

someone’s pets. I know that maybe the animals can be useful in medical research, but I

haven’t heard of any big discoveries being made from using animals. It’s usually for

stuff like make-up and it’s not fair to use animals in research to test the safety of

make-up.

Response: This is a very one-sided essay that shows little evidence of fairly considering the

evidence on multiple sides. The student barely mentions arguments for using animals in

research and discounts the possibility that useful discoveries have been made on the basis of

research with animals by saying that she hasn’t heard of any such discoveries. But there’s no

indication that she searched for whether there were any such discoveries. The claims she does

make (such as the claim that animal research is usually used to test make-up) are not

supported by any specific evidence. She does not critically evaluate her own claims.

Considering sample size. Suppose that Lexie, a high school student, is writing a paper on whether a
new fad diet is effective and safe. She reads a scientific study with over 1000 people that shows a slight
average weight gain among those following the diet and also demonstrates harmful side-effects of the diet.
She also reads the testimony of a single dieter in a magazine who describes how the diet has helped her lose
weight and turn her life around. To which piece of evidence should Lexie give more credence? Scientists
and social scientists would argue strongly that the study with 1000 people should be given more weight.
Other things being equal, evidence based on large samples (i.e., large numbers of people, animals, or other
objects of study) is more credible than evidence based on small samples or just a single case. Considering
sample size refers to taking the number of objects of study into account when drawing conclusions.
Effective reasoners prefer evidence based on larger sample sizes (Jacobs & Narloch, 2001; Watson
& Moritz, 2000). Ineffective reasoners do not pay attention to sample size, and indeed they often find
stories or vivid examples more persuasive than better data based on larger samples (Chinn, 2006; Nisbett
& Ross, 1980). As an example, consider this problem adapted from Fong, Krantz, and Nisbett (1986).

The Caldwells had long ago decided that when it was time to replace their car, they would get what they called

“one of those solid, safety-conscious, built-to-last Swedish cars”—either a Volvo or a Saab. As luck would have

it, their old car gave up the ghost on the last day of the closeout sale for the model year both for the Volvo and

the Saab. They quickly got out their Consumer Reports where they found that the consensus of the experts was

that both cars were very sound mechanically, although the Volvo was felt to be slightly superior on some