New York, Sep 2 (IANS): Small alterations to a person's appearance, such as wearing glasses, can significantly hinder positive facial identification, says a study which has future implications on identification for security purposes.

In the research, published in the journal Applied Cognitive Psychology, psychologists showed participants a number of faces in various 'natural' poses 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 and only one image wore glasses.

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.

"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," said Robin Kramer, professor at the University of York.

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.

"We hope that this research can be used by legal authorities to help inform future policies on identification for security purposes," said kay Ritchie, Professor at the University of York.