Ken MacQueen profiles two four-year old conjoined twins:

Tatiana and Krista are not just conjoined, but they are craniopagus, sharing a skull and also a bridge between each girl’s thalamus, a part of the brain that processes and relays sensory information to other parts of the brain. Or perhaps in this case, to both brains. There is evidence that they can see through each other’s eyes and perhaps share each other’s unspoken thoughts. ...

The way their heads are joined, they have markedly different fields of view. One child will look at a toy or a cup. The other can reach across and grab it, even though her own eyes couldn’t possibly see its location.

(Hat tip: Kottke)

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