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Complexity and Preference: A Hedgehog Theory

In mental activity of any sort, a moderate level of novelty and challenge is pleasurable. Too much change too fast is overwhelming and unpleasant. We seek to experience events which lie somewhere between chaos (on the one hand) and boredom (on the other). Dember and Earl proposed this idea in 1957, but Edward L. Walker developed it fully in his hedgehog theory of behavior (Walker, 1980).

The name "hedgehog theory" is a reference to a saying by the ancient Greek poet Archilochus, who said, "The fox knows many things, but the hedgehog knows one big thing." Foxes have a different trick for every situation. They are versatile and clever. Hedgehogs have only one trick (curling up into a spiny ball), and they use it in all situations, whenever they are vulnerable. And it is a very effective trick.

What is the "one trick" in Walker's hedgehog theory?


The Hedgehog (left) and its one trick (right)

Walker called his theory a hedgehog theory because, like the hedgehog, it has one trick. It explains all behavior using just one principle: the idea that subjective complexity determines preference.

Preference is measured by giving an organism free choice of alternatives to determine what it likes to do. Walker's theory holds that organisms prefer to do things that are neither too simple nor too complex. They seek activities that are at an optimum level of complexity.

The relationship between preference and complexity can be shown on an inverted-U shaped curve. The zero point represents a neutral hedonic reaction, neither pleasure nor pain. When complexity is too low, the line drops below zero. This means events are too simple, which makes them boring and unpleasant. When the complexity is moderate, enjoyment is greatest. When complexity is too great, events become unpleasant—chaotic and overwhelming.

What "critical ingredient" did Walker add to his theory?


The inverted-U function in Walker's Hedgehog theory

Walker's hedgehog theory adds a critical ingredient. As a person has repeated encounters with a complex stimulus, the brain's response is simpler and simpler. This means that a complex stimulus gets more enjoyable with repeated experience. It moves toward optimal complexity. But it also means that an optimal stimulus becomes simpler with repeated experience, eventually becoming boring.

In this way, the hedgehog theory explains why people move through a series of challenges in life. Each challenge starts by being too difficult, too complex. Then it becomes gradually more manageable and more exciting and enjoyable. Eventually it becomes boring, and the person moves on to new challenges.

The hedgehog theory explains a common phenomenon you may have noticed when encountering new forms of art. When you encounter a piece of music that is chaotic or difficult to interpret, for example, you may be repulsed. With repeated experience, you may begin to see a pattern in it. Eventually, you may learn to love it. It "grows on you." But no piece of music remains a favorite forever. With enough listenings, it becomes so familiar that you move on to something new.


The hedgehog theory in action

The hedgehog theory can be related to research on taste preferences. Youngsters who tried plain yogurt for the first time usually reported that it tasted worse than they expected. They did not like it. When forced to sample it repeatedly, however, 92 out of 151 subjects grew to like it more and more (Moses-Zirkes, 1993). Presumably the taste of plain yogurt was a bit of a shock at first, probably because it is more sour than the sweet yogurts most children have encountered. But plain yogurt is not bad, just different, and often, after a few encounters with it, the taste become more appealing. This is what the phrase adult taste refers to: a taste that grows on you with experience.

What pattern generally occurs as you master a demanding task?

This can happen with all manner of different stimuli, even academic subjects. A topic may seem confusing at first, painfully difficult to grasp. Gradually things fall into place. The subject becomes simpler as you encounter it repeatedly. Eventually you may find yourself enjoying it. Later, after you master it, you might enjoy moving on to more difficult things.

Although Walker formulated the hedgehog theory in the era before brain scans, the first part of his theory (psychological simplification with repeated experience) receives striking support from brain scanning evidence. As described in Chapter 3, people who are trying to master a new task show widespread activation in the brain. As they master a task, the area of activity shrinks. Eventually, when the task becomes automatic, the area is very small. The task is now easy, almost second nature. At that point, a person has the resources available (and the motivation, Walker would say) to master a new task.

But the hedgehog theory also says that, with enough repetitive experience, an activity that was once challenging will become too familiar, like plain yogurt consumed for breakfast, lunch, and dinner. The average person becomes tired of having the same stimulation all the time and, according to the hedgehog theory, is automatically motivated to move on to new challenges.


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