Little white lies have a tendency to snowball. The more we lie, the more our brains seem to become desensitised to deception.

Tali Sharot at University College London and her team ran an experiment that encouraged volunteers to lie. They were shown jars of pennies, full to varying degrees, and asked to send estimates of how many there were to partners in another room. The partners were shown blurrier images of the jars, so relied on the volunteers’ estimates to guess the number of pennies, in order to win a reward for each of them.

When the volunteers were told they would get a higher personal reward if their partner’s answer were wrong – and that the more inaccurate the answer, the greater the reward would be – they started telling small lies, which escalated. A person who might have started with a lie that earned them £1 may have ended up telling fibs worth £8, for example.

Brain scans showed that the first lie was associated with a burst of activity in the amygdalae, areas involved in emotional responses. But this activity lessened as the lies progressed (Nature Neuroscience, DOI: 10.1038/nn.4426). “This highlights the danger of engaging in small acts of dishonesty,” says Sharot.

My comment: Seems to me to be obvious. However, a small white lie to flatter, for instance, might be excused.
In general, however, lying is corrosive to the soul. Most people realise that as they grow up.