• Consider an ice cube sinks in one container of "water," but floats in another.
• Or the behavior of a common compass: The N of the floating magnet points north. Why ?

• They also have no confidence in their own judgement. Don't like poles repel each other ?
• Or the challenge: Which end of a wind vane points toward the wind ?
• Or this question: Could a 7ft NBA player view his full image in a 4ft mirror ?
• Could a kindergartner lift her teacher with an 8ft 2x4 ?
• How much force is required to lift a 5 # brick with a fixed pulley ?

"A general principle must be operating here," alert teachers must realize, when time and again certain science experiments motivate even inattentive and less alert students. In deed, the need for consistency would seem to explain student response to the floating pumice or sinking ice cube.

Consistency theory explains the wide-awake response of students -- even adults -- to the seemingly illogical results of science investigations. Basic to consistency theory is the tenet that the human mind is intolerant of such discrepancies.

Cognitive dissonance , one of the family of consistency theories, refers to an inconsistency between two cognitions or between one's actions and beliefs. For example, devoted sunbathers may experience dissonance when informed that too much exposure can cause skin damage and even cancer.

Cognition A: excessive sunlight damages the skin.
Cognition B: I expose myself to excessive sunlight.

• They can decide that the bronzed look is worth it; skin damage is years down the road;
• They can reject the claim that sunlight damages skin; or
• They can pass up the bronzed look.

Dissonance:
Cognition A: ice floats in water.
Cognition B: ice sinks in water.

Consonance:
Cognition A: ice floats in liquids having greater density, including water.
Cognition B: ice sinks in liquids having less density, including alcohol.

Similar outlines can be written for the fixed pulley - easily confused with a movable one; the compass; with is north-seeking pole; the full-length mirror for the NBA player; the kindergartner's wooden levers, and the crazy wind vane whose tail points toward the wind.

Putting this theory into action in the classroom requires that the students experience temporary dissonance, or frustration, that is consciously planned by the teacher. Withholding information, at least for the moment, provides the heartbeat of the teaching strategy.

Here is how I handle the sinking ice cube phenomenon. With all students watching, I take two identical glass containers, each half - filled with a clear liquid, and drop an ice cube into Jar A. The ice floats. I then drop an ice cube into Jar B. The ice sinks.

I wait for a response.

If no one responds within 20-30 seconds, I ask the class if they observe anything that bothers them. I list their responses on the board.

I ask them how Jar A differs from Jar B and again list their responses on the board.

If someone asks, "Is the liquid in Jar A water ?" I say, "Yes."
If someone asks, "Is the liquid in Jar B alcohol ?"
or says, "I know Jar B has alcohol in it; I can smell it."
I ask, "How would alcohol explain the behavior of the ice cube in Jar B ?"

Finally, I guide the students to a conclusion by a comparison of the liquids:
How are the liquids different ?
If the ice floats, which is heavier (or more dense), the liquid or the cube ?
If the ice sinks, which is more dense, the liquid or the cube ?"

I try to bring closure, or resolution, to a discrepant event, or at least begin to,by the end of one class period. I have seen students "chuck the whole thing" in frustration when a teacher adamantly withheld an answer, as if it were an exclusive secret.

That discrepancy can generate an overload of frustration was illustrated at an inservice meeting where teachers had sat through a lengthy inference demonstration using a mystery box with objects sealed inside. Announcing that they should learn to live with the unknown, the science educators refused to open the box for inspection or tell the participants what is contents were. During the break, one teacher, who until that point had been poised and cooperative, bolted to the table on which the box had been left, and ripped off the lid to see what was inside.

It is the "not knowing" that drives scientists to investigate.

Many science investigations at the K-6 level have the potential for the unexpected. For the very young, there is even an element of surprise in their first magnet, a bulb-battery-wire circuit, or sprouting seeds. For older children, "The Believe It Or Not Weather Quiz" and Wright's list of discrepant events would be a good place to start.

Knowing the motivating power of the discrepant event and understanding its base in consistency theory may inspire us to take full advantage of this teaching strategy. We can consciously and wittingly wring from such science investigations a full measure of surprise, challenge thought, and inquiry.