It's what some wives and girlfriends have long suspected. Just the sight of an attractive woman can make a man more dishonest, a study has found.

It seems male brains are so deeply hard-wired to compete for a mate that their devious side can be awakened simply by suggestive photographs.

Researchers found men were more likely to pocket small sums of money they were not entitled to after looking at images of beautiful women in seductive poses.

For the first test, at Taiwan's National Sun Yat-sen University, 74 men in their late teens and early twenties were split into two groups. One viewed a series of sexualised - though not explicit - pictures, while the other looked at non-sexual images of women.

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They then all completed a test of self-control, being asked to swiftly identify colours written in an incongruent setting - for example the word 'red' against a blue background.

Each participant had been promised 120 Taiwanese dollars (NZD $5.60) for their time - but, at the end of the study, received an envelope containing $170 (NZD $8).

Those who had seen the suggestive pictures were more than twice as likely to walk off with the extra cash, with only 54 per cent honestly handing back the excess, compared to 78 per cent of the other group. The men shown the sexual pictures also performed far worse on the self-control test.

The second experiment featured 90 men with an average age of 30, split into three groups.

Some saw racy images, some non-sexualised photos and the others no pictures at all.

They were all assessed for self-control before receiving a sheet of 20 maths questions and being asked to answer as many as possible in five minutes. The men were then allowed to mark their own answers and told they could help themselves to one dollar (just under 50 cents) from an envelope for each one they got right.

On average, those who had viewed the sexualised images added an extra three marks to their score, compared with only one mark in the other groups.

A further test on volunteers of both sexes showed that only men tended to lose self-control after seeing seductive pictures.

The study, published in the journal Evolution and Human Behaviour, said: "Exposure to mating-evoked stimuli - for example, pictures of sexually appealing women - leads to lower self-control and increased dishonesty among men. This research demonstrates that sexy women can seduce men away from behaving honestly and may more readily attract males who lie."

Lead author Wen-Bin Chiou, a professor of psychology, suggested that an increase in sex scenes on television may be having a corrosive effect on men's morals.

British psychosexual counsellor Pauline Brown said: 'These results were seen with racy pictures so we can only imagine how the effect will be amplified by men viewing pornography. Often I treat couples where the man has been living almost a secret double life involving porn, and dishonesty has become part of everyday routine.

"We will soon see the profound corrosive effects of having sexual material so readily available as this millennium generation grows up."