The Logic of Hands-On Science Instruction

Hands-on science instruction seems like a self-evidently good idea. Letting students observe and manipulate objects puts science concepts right in front of them, and sometimes literally in their hands. Not only is 500 ml of water twice as much as 250 ml on paper, in the lab it looks like twice as much. The concept of density is almost impossible to “grasp” without holding different objects of the same size but different weights (a plastic and a steel marble, for example) in our own two hands—once we do, the concept becomes entirely clear. Yet a hands-on approach to science education also has particular developmental value to elementary school students.


Concrete Operations

In my last post, I presented a graph of the relationship between Piaget’s developmental stages and age. We saw that elementary school spans three of these major stages—pre-operational, concrete operations, and formal operations. Now, if we highlight the amount of time elementary students spend in concrete operations versus pre-operational and formal operations (see figure below), we can appreciate just what a major portion of elementary school is spent in this particular developmental stage.

The concrete operations stage is characterized by the ability to begin logical reasoning. A child in this stage can begin to organize their thoughts in a coherent manner. However, their thinking is primarily limited to actual physical objects – thus the term “concrete”. Mental representations and abstract thinking are very difficult in concrete operations. Therefore, learning by manipulating physical objects—hands-on learning—is a natural fit for the concrete operations stage.



Another way to look at concrete operations is to think of it in terms of externalization. How often do we see elementary school students count on their fingers, read aloud to themselves or have to touch or hold things or objects they are talking about? These are all ways of externalizing their thinking. Even though older children and adults in the formal operations stage are capable of abstract thinking and internalized problem solving, they nonetheless frequently rely on externalizations and concrete manipulations in everyday life.

Jim Watson and Francis Crick used concrete operations and externalizations in solving one of the most intriguing scientific puzzles of the twentieth century—the chemical structure of DNA. They cut out pieces of paper to represent the various pieces of the DNA molecule and arranged them in different arrays on a table. One cannot help but see two fourth graders working together when imagining these two great scientists huddled over their paper models.

Adults use externalization methods all the time to solve problems. A good example is in mathematical problem solving. In solving addition problems it is usually much easier or even essential to externalize the problem - to write it down on paper and look at it. For example, try the following addition: 44 + 55 + 66 in your head (internally).

We are more accustomed to solving a problem such as this through externalization, writing it on paper as follows:

When doing this math, many of us will add the three numbers in the right-hand column (4 + 5 + 6 = 15), write a 5 under the line, and then “carry” the 1 above the 4 in the left-hand column (see below). In doing so, we have externalized the number 1. Instead of keeping it in our head (internalization), we write it down on paper (externalization), so we don’t lose it!

Russell Barkley makes an interesting point when discussing Attention Deficit Hyperactivity Disorder (ADHD) children. According to Barkley, “Children with ADHD do not seem to be able to play around with mental information as well as others….”  “I think it may be helpful, therefore, to find ways to represent a problem and its alternative solutions in a more physical way.”  “….So whenever problem solving of any type must be done, see if you can think of some way to make the problem and the parts of possible solutions physical so that your child can touch them, manipulate the pieces, move them around, and come up with new arrangements of the pieces of information that might help him solve the problem.”1 

I would suggest that this concept of externalizing pieces of information extends well beyond the ADHD patient and that it lies at the heart of the hands-on concept of science education. This is especially true for students in the concrete operations stage. These are students who are capable of solving problems, but only if they are presented in terms of physical objects. These are students that cannot internalize well and are severely challenged or incapable of abstract thinking. These are also the bulk of elementary school students.


  1. Barkley, R.A. Taking Charge of ADHD: The Complete, Authoritative Guide for Parents. The Guilford Press, 2000, p. 150.





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