Psychologists think they've found a new explanation for a classic mistake made by babies.
If you repeatedly hide an object under an opaque cup, each time allowing a ten-month-old baby to retrieve it, and then you hide it one last time under a second cup - where do you think the baby will look for it? The chances are, she'll probably look under the first cup, even though she's just that moment watched you put it under the second!
It's a strange mistake and one made famous by the grandfather of developmental psychology, Jean Piaget. The great man believed babies make this mistake because they've yet to grasp the idea that objects continue to exist even when they can't be seen. By his account, babies think the object will come into existence as a consequence of their act of looking.
More modern explanations think the mistake has more to do with memory or the inability of babies to inhibit their temptation to look under the first cup - they've found it under the first cup so many times, they can't stop themselves from looking there again.
But now Jozsef Topal and colleagues have provided evidence supporting an alternative explanation. They argue that when we communicate with babies using eye-contact and chirpy chatter, they have an innate tendency to assume that what we're communicating to them is a general fact about the world.
So when you hide the object under the first cup and you look and talk to the baby, she thinks you're telling her that this type of object is generally found under this cup.
Topal's team tested this explanation by performing the hiding test with three groups of ten-month-olds. For one group, the adult tester sat at right-angles and made no eye contact or communication with the babies. When the object was finally hidden under a second cup (after being repeatedly hidden and retrieved from a first cup), lo and behold, the babies were far more likely in these conditions to subsequently look for it in the right place (57 per cent of them did so, compared with 14 per cent of babies who were tested under typical conditions involving eye-contact and talk).
For the final group, the hiding task was performed with the tester concealed behind a curtain - these babies looked for the object under the second cup 64 per cent of the time.
Topal's team aren't saying that inhibition and memory don't have anything to do with this classic error - after all, even without eye-contact and talk the babies did still sometimes look in the wrong place. However, they say their account has the advantage of explaining why, under usual conditions, babies nearly always look in the wrong place (if they were simply clueless, you'd expect them to look in the correct place at least half the time).
"Human infants are highly social creatures who cannot help but interpret the ostensive communicative signals directed to them," the researchers wrote. "Although such a disposition prepares them to efficiently learn from adults, in certain situations it can also misguide their performance."
J. Topal, G. Gergely, A. Miklosi, A. Erdohegyi, G. Csibra (2008). Infants' Perseverative Search Errors Are Induced by Pragmatic Misinterpretation Science, 321 (5897), 1831-1834 DOI: 10.1126/science.1161437