neurodudes

Anna Fisher and Vladimir Sloutsky have an interesting paper called “When Induction Meets Memory: Evidence for Gradual Transition From Similarity-Based to Category-Based Induction”. They are trying to get at the question of whether children around the age of six have category-based induction or similarity-based induction.

What is category-based induction and similarity-based induction?
If I tell you that object A has property P and object B does not, and then I show you objects X, Y, and Z and ask which ones probably have property P, how do you make the decision?

Do you rely on which categories the objects fall into? (”object A is a mammal and object B is a fish; X and Y are mammals, and Z is a fish, so I’ll guess that X and Y have property P, and Z does not”)

Or do you rely on similarity? (”object A is brown and object B is yellow; X and Z are brown and Y is yellow; so I’ll guess that X and Z have property P, and Y does not”)

Humans apparently tend to prefer category-based induction, at least when they are familiar with the categories. What about children around age 6? This study argues that they prefer similarity-based induction.

Please refer to the paper if you’d like a more detailed explanation, as well as a discussion of the history of the question and citiations to other experiments supporting similarity-based or category-based induction in children.

The details of the study
In the control condition, subjects were given pictures of animals and told to study them for a subsequent recognition test. In the experimental condition, subjects were given a picture of a cat, and told that it has “beta cells inside its body”. Then they were given pictures of other animals, some of which were also cats, and asked which animals had beta cells inside their bodies.

In both conditions, subjects were later shown some of the same pictures and some different ones, and asked which pictures they had seen before (a recognition test).

Adults (and 11-year olds) in the experimental condition were worse than adults (and 11-year olds) in the control condition at the recognition test. But kids of age 7 did about the same in both conditions.

The experimenters argue that this is because the adults in the experimental condition were doing category-based induction and the 7-year-olds were doing similarity-based induction.

More details

They support this assertion by redoing the experiments with some twists. Most notably they redo it with 7-year olds, but only after training them to do category-based induction (see page 590 of the paper for how they did this). These 7-years performed similar to adults on the recognition-memory test. This supports the assertion that the difference between the 7-year olds and the adults was the use of category-based induction.

They also do the opposite experiment, where they create a situation in which the adults don’t know what the categories are and so are forced to use similarity-based induction. In this case, the adult performance on the recognition test becomes similar to the children’s.

Discussion
This paper is methodologically similar to the pigeons study, although they are about different things. In both studies, we first identify a cognitive task that someone else can do better than human adults (someone else being children or pigeons). This in itself is interesting, because it implies that there are tradeoffs in “intelligence”, and that the greater performance of human adults on some tasks comes at the price of worse performance on others (see Chris Chatham’s weblog entry on this study for more on this).

It also allows us to do interesting experiments. In both studies, the researchers wanted to identify the cause of the bad performance of human adults. They did this by training the group who used to be better than human adults to be just as bad as them (or almost just as bad). This strongly suggests that whatever they taught the others was the cause of the bad performance in the human adults. It also shows that what they taught the others was something that they weren’t doing before.

So, in the case of the pigeons, the researchers conclude that prior experience with matching tasks was the cause of the base rate neglect in the human subjects. In the induction study, the researchers conclude that children around age 6 don’t normally prefer category-based induction.

This entry was posted on Friday, January 6th, 2006 at 7:11 pm by Bayle Shanks and is filed under Cognitive science. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.