Girlfriends and wives may find it exasperating when their man does not show empathy when they complain or when they caught their man gazing at other woman. But a new book suggests that they should be relief that such behaviour is normal.

In The Male Brain, Louann Brizendine, an American psychiatrist, follows up her controversial 2006 bestseller The Female Brain, which famously -- and incorrectly -- claimed that women use an average of 20,000 words a day compared with only 7000 for men, and explores how the differences between the male and female brains often lead to misunderstandings and unintended consequences.

Her conclusion that the male brain, marinated in testosterone since the eighth week of conception, is hard-wired to cause men to lie, take risks and suppress their emotions, is equally contentious, appearing to suggest men's behaviour is devoid of personal responsibility and social conditioning.

Is your teenage son bored and surly? Blame the hormones. If testosterone were beer, Brizendine suggests, a nine-year-old boy would be getting the equivalent of a quarter-litre a day, but by the time he is 15 he is awash with the equivalent of nearly nine litres a day of it. It blunts his ability to read facial expressions and heightens his sensitivity to criticism.

He doesn't just look bored. He is bored. The testosterone-drenched reward centre in his brain requires extraordinarily intense sensations to be activated; it's why he likes all those shoot-'em-up video games.

Maybe you are dating. Do not take it personally if your lover falls asleep immediately after sex. Post-coital narcolepsy is caused by a blast of the pleasure hormone oxytocin released into the hypothalamus after orgasm.

This makes women want to cuddle and talk. In men, for reasons we don't understand yet, it works a lot like a sleeping pill, Brizendine explains.

Or perhaps you complain to your man about a particularly tough problem at work. He immediately suggests a solution. Are you grateful? Hell, no. All you wanted him to say was, I understand how you feel. This doesn't come naturally to him, however, because in men the analyse-and-fix-it circuit in the brain, known as the temporalparietal junction system, dominates the emotional empathy circuit, or mirror-neuron system. In women it's the other way around.

On one level the book reads like one big get-out-of-jail-free card for men. But Brizendine insists it is not. If we know how a biological brain state is guiding our impulses, we can choose how to act, she says.