Picking a flattering photo for an online dating or networking site is best left to a stranger, a study has shown.

Selfie images people select themselves are less likely to convey a favourable first impression, say psychologists.

Previous research has demonstrated that assumptions about character and personality based on a photo are made within a split second.

Lead study author Dr David White, from the University of New South Wales in Sydney, Australia, said: "Our findings suggest that people make poor choices when selecting flattering images of themselves for online profile pictures, which affects other people's perception of them.

"This effect is likely to have a substantial impact on online interactions, the impressions people form and the decisions they base on them, including whether to employ, date, befriend or even vote for someone."

He added: "Our results have clear practical implications; if you want to put your best face forward, it makes sense to ask someone else to choose your picture."

For the study, published in the journal Cognitive Research: Principles and Implications, the researchers asked 102 students to pick out two photos of their own face from a selection of 12.

The two pictures were the ones they would be most and least likely to use as a profile picture in social or professional networking or internet dating.

Each volunteer was then asked to make the same choices from 12 images of a randomly selected study participant.

When self-selected images were shown to a group of independent viewers, they were rated less highly for attractiveness, trustworthiness, dominance, confidence and competence than those chosen by others.

"Future research needs to investigate the mechanisms that underlie the choices people make when selecting profile pictures to find out why people seem to have a limited ability to select the most flattering images of themselves," said Dr White.