"The dinner party guest who puts his foot in his mouth could lack a crucial mental ability that stops the rest of us from blurting out our true feelings," according to a report in the July issue of Psychological Science, a journal of the American Psychological Society.

But while most people can usually avoid telling painful truths by inhibiting themselves, the results of experiments conducted by University of New South Wales psychological researcher Bill von Hippel suggest that we should be extra wary of making social blunders when we are under strain or fatigued.

The ability to behave in a socially appropriate way was assessed by asking 71 participants to eat a chicken's foot under conditions of high or low social pressure, von Hippel reported.

People in the high-pressure group were served the foot by a Chinese woman who described it as the national dish of China and her personal favorite, while those in the low-pressure group were served the foot by a non-Chinese woman who had said only that it was Chinese food.

Before the experiment, participants' ability to hold their tongues — called inhibitory ability — was measured with a test that assessed their ability to suppress irrelevant or inappropriate thoughts.

"People who responded most negatively to the chicken foot dish under high social pressure turned out to be those who also performed worst on the inhibitory ability test," von Hippel said. "They were much more likely to make a disapproving face and a negative statement such as: 'That's bloody revolting!' "

"We found that people with poor inhibitory ability were more likely to behave in a socially inappropriate way than people with good inhibitory ability. But even people with good inhibitory ability were likely to behave inappropriately when distracted. This suggests that our ability to suppress our true feelings is disrupted under demanding conditions.

"It's well established that older people, very young people and some brain-damaged people have less inhibitory control over thought and action. However, this new research suggests that important variations occur in the general population in this inhibitory ability — some of us are naturally better at holding our tongue than others," von Hippel said.

"Many people may be unable to inhibit the tendency to blurt things out even when they know the rules of social behavior and want to behave appropriately.

"It's likely that people who can inhibit their true feelings in a challenging social situation have a greater chance in succeeding in jobs requiring a high degree of social etiquette, such as international diplomacy. But even experienced career diplomats may find it increasingly difficult to act appropriately if they are distracted or fatigued, or as they grow older. That's an area of research we're investigating right now."

Note: If no author is given, the source is cited instead.

• Intelligence
• Perception
• Social Psychology
• Psychology
• Memory
• Relationships

• Illusion of control
• Self-esteem
• Anger management
• Social psychology
• Self image
• Emotional detachment