Evaluating claims in child development

Jean Mercer writes the Child Myths blog in Psychology Today. She posted a couple of days ago about how to evaluate things people tell you about child development (besides checking snopes.com). It's worth reading (as is the blog).

She refers to a philosopher she became acquainted with in college, Stephen Toulmin, who pointed out three things you have to have to prove an argument:

• A claim.  You have to say what you think is true.
• A ground. There has to be some evidence or reasoning, not just an assertion.
• A warrant. There has to be some connection between the evidence or reasoning and the conclusion.

As an example, she applies this to the statement that adopted kids and their new parents can develop emotional attachment with each other by the act of staring into each other's eyes.

• The claim is a little dodgy, because there's no good way to assess emotional attachment in school-age kids. 
• The grounds for believing it are that babies and toddlers and mothers gaze into each others's eyes, and they get attached. Mercer accepts this, because mutual gaze happens when attachment is forming, but the problem I see with this is we don't know which way the causal relation goes. Maybe they look into each other's eyes because they are attached.
• The warrant fails for that very reason, she says, because we don't know that the gazing causes the attachment. Also, there's no reason to believe that what works for babies will work for 4th graders.

It's a good blog, and this is a good exercise to go through (if not necessarily formally) when you see a new claim in child development.