It is often said that you never get a second chance to make a first impression. This popular saying contains more truth than many people realise. Research in psychology has consistently shown that we form opinions about other people astonishingly quickly – sometimes within a tenth of a second of meeting them. In that brief moment, before a single word has been spoken, we make judgements about whether a person is trustworthy, competent, likeable or aggressive.

These rapid judgements are based on a range of signals. Facial expressions, posture, clothing and tone of voice all feed into the impression we form. Interestingly, studies suggest that first impressions, though quick, are often surprisingly accurate – but not always. The danger is that once an impression has formed, it is remarkably difficult to change. Psychologists call this the “halo effect”: if we decide that someone is likeable, we tend to assume they also possess other positive qualities, such as intelligence or honesty, even without evidence. The reverse is also true.

This has significant consequences in everyday life. In a job interview, for example, the impression a candidate makes in the first few seconds may influence how the interviewer interprets everything that follows. A confident, well-presented applicant may be given the benefit of the doubt, while an equally qualified but nervous one may struggle to recover from a shaky start. The same effect operates in courtrooms, classrooms and first dates.

What can we learn from all this? On the one hand, it is worth being aware of the impression we create, particularly in important situations, since small details can matter more than we might like to admit. On the other hand, we should be cautious about trusting our own snap judgements of others. First impressions are useful, and they exist for good evolutionary reasons, but they are far from infallible. The wisest approach is to make a good first impression when we can – and to remain willing to revise the impressions we form of other people.