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These are two …?" she showed that even very young children internalize the word-building rules of language and can produce correct examples of those rules ("wugs") that they had never heard before.

There is still, of course, the potential hazard of exposing intimate details of a child's life that he or she might not like to have exposed.

In those days there was plenty of philosophical discussion about the nature of children and what they knew when: Were they blank slates, or did they possess innate knowledge?

At the recent conference of the Cognitive Science Society, Roy's team presented a paper that turned the microscope on the parents, showing how the way they alter the complexity and prosody of their speech influences the way the child learns.

The more all-encompassing and detailed the study of child language becomes, the more we end up looking at what goes on around the child.

But as long as scientist parents follow professional guidelines about subject privacy and leave highly personal information out of their studies, kids are more likely to feel violated by their parents' YouTube accounts than by their journal articles.

It’s become the norm in America for parents to capture their children's smiles, tantrums, and impish shenanigans—sometimes cute, sometimes deeply embarrassing—on blogs, YouTube videos, and Twitter feeds.

Roy's decision to use his own child as a research subject makes people uncomfortable: When the New York Times wrote a story about Roy, the comments were on the outraged side.

But as long as scientist parents follow professional guidelines about subject privacy and leave highly personal information out of their studies, kids are more likely to feel violated by their parents' YouTube accounts than by their journal articles.

But it's crucial to realize that while Roy's using the latest technology, his tactic is not new: Language researchers have long used their children as subjects.

Parent-child studies helped popularize the use of empirical research in linguistics; they have inspired new theories and exposed facts about language behavior that no one had yet considered.

Roman Jakobson, one of the most influential linguists of the 20th century, pulled from these studies to support his theory that languages are not collections of particular sounds, but systems of contrast.

All parents feel a sense of wonder as they watch their children piece together their first words, and their first phrases; scientist parents can't help but feel professional curiosity as well.

By Arika OkrentPosted Wednesday, Sept. 8, 2010, at 4:14 PM ET
Portrait of Dietrich Tiedemann, one of the first philosophers to publish a study about his own child's language acquisition.

Parent-child studies helped popularize the use of empirical research in linguistics; they have inspired new theories and exposed facts about language behavior that no one had yet considered.

It's lucky that the obscure 1919 study "Parallel learning curves of an infant in vocabulary and in voluntary control of the bladder" was made in the pre-video era.

(Their approach didn't have much of an impact on science.

Yet researchers continued to use their own children as subjects, because the practice was always and will always be more than a matter of convenience.

Roy's decision to use his own child as a research subject makes people uncomfortable: When the New York Times wrote a story about Roy, the comments were on the outraged side.

But it's crucial to realize that while Roy's using the latest technology, his tactic is not new: Language researchers have long used their children as subjects.

But it wasn't until the 1900s that parents went beyond jotting down things that struck them as interesting and started keeping thorough journals of everything their kids said.

She subsequently sent him a list of 100 slips that her daughter had made before the age of 3.

There is still, of course, the potential hazard of exposing intimate details of a child's life that he or she might not like to have exposed.

One of the early notable studies of a child by his parent was published by the philosopher Dietrich Tiedemann in 1787.

His study didn't settle the blank-slate debate at the time, but it encouraged others to try an empirical approach to scholarship.

So they logged over 4,600 entries on her potty "successes" and "accidents."

It's lucky that the obscure 1919 study "Parallel learning curves of an infant in vocabulary and in voluntary control of the bladder" was made in the pre-video era.

But MIT professor Deb Roy makes even the most obsessive at-home documentarians seem inattentive: He recorded, on video and audio, nearly every waking moment of the first three years of his son's life—not as an exercise in parental vanity, but in the name of science.

Ironically, however, Roy's study indicates that the balance of power could shift as technology becomes more sophisticated.

Recording a child for amusement is one thing, but taking those recordings to the lab for analysis may be quite another.

Parent-child studies helped popularize the use of empirical research in linguistics; they have inspired new theories and exposed facts about language behavior that no one had yet considered.

His study didn't settle the blank-slate debate at the time, but it encouraged others to try an empirical approach to scholarship.

At the recent conference of the Cognitive Science Society, Roy's team presented a paper that turned the microscope on the parents, showing how the way they alter the complexity and prosody of their speech influences the way the child learns.

In 1962, Ruth Weir published Language in the Crib, a study of the monologues her toddler son produced alone, while drifting off to sleep.

Now Roy and his team have begun the enormous task of trying to make sense of the data—all 120,000 hours of it.

Such information had never been catalogued in this way or in this quantity before, and it helped advance the field of linguistics.

He rejected anecdotal evidence and out-of-thin-air wisdom, relying instead on carefully recorded observations.