Many a parent has been driven to the point of madness by successive "why?" questions from preschoolers, but it's a good sign that they ask and they do better if they get a detailed explanation than if you just answer 'because.'

The researchers carried out two studies of 2- to 5-year-olds, focusing on their "how" and "why" questions, as well as their requests for explanatory information, and looking carefully at the children's reactions to the answers they received from adults. In the first study, the researchers examined longitudinal transcripts of six children's everyday conversations with parents, siblings, and visitors at home from ages 2 to 4. In the second study, they looked at the laboratory-based conversations of 42 preschoolers, using toys, storybooks, and videos to prompt the children, ages 3 to 5, to ask questions.

By looking at how the children reacted to the answers they received to their questions, the researchers found that children seem to be more satisfied when they receive an explanatory answer than when they do not. In both studies, when preschoolers got an explanation, they seemed satisfied (they agreed or asked a new follow-up question). But when they got answers that weren't explanations, they seemed dissatisfied and were more likely to repeat their original question or provide an alternative explanation.

"Examining conversational exchanges, and in particular children's reactions to the different types of information they get from adults in response to their own requests, confirms that young children are motivated to actively seek explanations," according to the researchers. "They use specific conversational strategies to obtain that information. When preschoolers ask 'why' questions, they're not merely trying to prolong conversation, they're trying to get to the bottom of things."

The moderate sample size means that the study cannot be generalized to all children, but the research clearly suggests that by age 2, children contribute actively to the process of learning about the world around them.

The study, by researchers at the University of Michigan, appears in the November/December 2009 issue of the journal Child Development.