Bathsheba and Slooow_Joe -
if memory serves, the author puts forward the premise that perception in the speices is governed by early man's demarcation of domestic tasks.
The man went out hunting, so his distance vision - looking for animals at a distance, was sharp, but his near vision was poor. The woman, looking after the cave and children had better near vision, and could easily spot close objects, but her distance vision would be poor.
That is why modern man can look for a close object and literally not see it, when a wman spots it right away.
Simiarly, the woman's tasks including watching the fire, watching the children, cooking and so on, allow her to multi-task naturally, wheras the man, with one task to complete, finds it difficutl.
The premises in the book revolve around the fact that although we are civilised, our civilsation is a thin veneer, and underneath it, these primal instincts and behaviours still affect the way we behave today.