If you chuckled at Superman's transformation, you may have been wrong.

Experts have found that a simple act just as Clark Kent donning a pair on glasses really can confuse people so much they don't recognise you.

They say the research could help improve identification of people by police and at passport checks.

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Christopher Reeve in Superman as Clark Kent: Researchers at the University of York have shown that small alterations to a person's appearance, such as wearing glasses, can significantly hinder positive facial identification.

'The question of whether the inhabitants of Metropolis could be realistically deceived by Superman's simple disguise has been rumbling since the comic books first arrived on the stands, but the question becomes a serious one when applied to real-world security issues,' said Dr Robin Kramer, from the University of York's Department of Psychology.

'When a security guard checks a passport photo against the person standing in front of them, they do not have the luxury of familiarity with that face, as Lois does with Superman/Clark Kent.'

Psychologists showed participants a number of faces in various 'natural' poses, similar to images seen on Facebook or other social media sites, and asked them to decide whether each pair of images showed the same person or not.

Images were shown in three categories - pairs of faces that wore glasses, images where neither wore glasses, or only one image wore glasses.

Psychologists showed participants a number of faces in various 'natural' poses, similar to images seen on Facebook or other social media sites, and asked them to decide whether each pair of images showed the same person or not.

In cases where both of the faces wore glasses or where neither wore glasses, accuracy was around 80 per cent.

However, when only one of the two faces wore glasses, performance was approximately 6 per cent lower, a statistically significant decrease.

'We also know from prior work that it is easier to match passport-style photos together when the facial expressions and poses are the same,' said Kramer.

'Here, we investigated unfamiliar face matching, showing participants two unconstrained faces of strangers, with and without glasses, and asked whether the images are the same person or two different people.'

Dr Kay Ritchie, from the University of York's Department of Psychology, admitted that Lois Lane probably shouldn't have been fooled by the disguise.

The results suggest that people generally find it difficult to correctly match unfamiliar and uncontrolled face images, but they are significantly worse when glasses are worn by only one of the faces.

However, Dr Kay Ritchie, from the University of York's Department of Psychology, admitted that Lois Lane probably hadn't been fooled.

'In real terms, glasses would not prevent Lois recognising that Clark is in fact Superman as she is familiar with him.

'For those who do not know him, however, this task is much more difficult, and our results show that glasses do disrupt our ability to recognise the same unfamiliar person from photo-to-photo.