August 28, 2009 10:33 PM   Subscribe

Please help me remember the name of this stage of psychological development, where you can begin to discern the volumetric differences between containers of different sizes.

Some time ago I remember reading an anecdote about a psychologist who was visiting his friend's family. The family consisted of the mother and the father, both also psychologists, and a five year old boy and seven year old girl.

As he was helping prepare lunch, he showed the boy two different glasses and said, "which holds the most water?"

And the boy said, "I'd say this one, but you should ask my sister. She already has XXXXX".

What is XXXXX?
posted by Sutekh to Science & Nature (6 answers total) 1 user marked this as a favorite
posted by No New Diamonds Please at 10:43 PM on August 28, 2009

It's from Piaget -- I think you're thinking of the concrete operational stage (ages 7-12, more or less), before which children have difficulty with conservation of quantity: so if you pour water from long, thin container A to short, fat container B they will say there is less water in B.

I am not sure how much psychologists today buy into this aspect of his theories, though. (Meant literally - I just don't know, though I do know that knowledge about other aspects of his theories has been refined and changed since his day).
posted by forza at 10:49 PM on August 28, 2009

You're thinking of Piaget's conservation experiment. A child who would say one glass has more water is in the preopeeational phase. A child who knows that the volume doesn't change is in the concrete operational phase.
posted by eendje at 10:51 PM on August 28, 2009

Nthing Piaget. Concrete Operational.
posted by Bueller at 1:18 AM on August 29, 2009

OMG conservation is totally what I was looking for!!! Thank you all SO MUCH.
posted by Sutekh at 5:17 AM on August 29, 2009

An old psych joke goes, "developmental psychologists don't have children; they have subjects."
posted by Eamon at 8:43 PM on August 29, 2009

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