Lying lengthened Pinocchio's nose, but research suggests the more falsehoods we tell, the more it shortens our lives.
Fibbing releases stress hormones that can increase heart rate and breathing, slow digestion and cause tension and hypersensitivity in muscles and nerve fibres.
When we lie, blood pressure in the heart rises - and polygraphs pick up the change. Lying often enough, long enough can damage the heart and arteries.
Researchers at the University of Notre Dame carried out a 10-week honesty experiment with 110 people, half of whom were instructed to stop telling major and minor lies during the test. The rest got no special instructions about lying.
Both groups went to a lab each week to complete health and relationship surveys and to take a polygraph test assessing the number of major and "white" lies they had told that week.
"We found that the participants could purposefully and dramatically reduce their everyday lies, and that in turn was associated with significantly improved health," Anita Kelly, the psychology professor who led the study, said in a statement.
The link between less lying and improved health was significantly stronger in the no-lie group. When people in that group told three fewer white lies than they did in other weeks, they experienced about four fewer mental-health complaints, such as feeling tense or melancholy, and about three fewer physical complaints, such as sore throats and headaches.
When people in the control group told three fewer minor lies, they reported two fewer mental health complaints and one less physical complaint. The pattern was similar for major lies.
In weeks when participants told fewer lies, they reported that their close personal relationships had improved and that their social interactions overall had gone more smoothly.
At the end of the study, Kelly said, members of the no-lie group were asked to tell how they managed to be less deceptive. Some said they realised they could simply tell the truth about accomplishments rather than exaggerate, others said they stopped making false excuses for being late or failing to finish tasks. Still others evaded telling lies by responding to a difficult question with another question to distract the person calling them on the carpet.
The study underscores that in addition to physical harm from lying, the practice also damages trust and causes people to avoid dealing with emotions or problems that boost emotional stress.
Scientists know that lying actually makes the brain work harder. Radiologists at Temple University reported as far back as 2006 that they were able to see the extra effort in more brain areas when study subjects were lying.
It seems the brain has to fire up more regions to lie, because we're simultaneously suppressing the truth, coming up with an alternative and trying to keep our story straight. An average of 14 regions were activated when lies were told, compared to seven when subjects were honest.
A lot of research has shown that when we lie, we give shorter responses, make more speech errors, blink more and fidget more, but have no trouble looking the person we're lying to directly in the eyes. But it's almost impossible to spot subtle differences in a particular person who's lying.
The traits also extend to written communication - and may be easier to detect, according to research published by University of Wisconsin and Cornell University scientists.
They analysed personal descriptions written for internet dating profiles used on four matchmaking sites. They compared the actual height, weight and age of 78 online daters to the information and photos they posed.
About 80 per cent of the profiles differed from the truth to some degree. The results were published in the Journal of Communication.
The researchers found that the more deceptive someone was on a profile, the less likely they were to use "I" in the profile - a bid to distance themselves from the deception.
They'd say they were "not boring" rather than "exciting". And their self-descriptions were generally shorter, to avoid saying too many things that might trip them up later.
Liars who had fibbed about age, height or weight or posted a deceptive photo were also less likely to discuss appearance in profiles, talking instead about work or life achievements.
Using those markers, the researchers were able to identify who was lying on their profile about 65 per cent of the time. When they asked untrained volunteers to rate the trustworthiness of the profiles solely on the written descriptions, few were able to spot deception.