A lack of human interaction makes it easier to steal from self-service checkouts in supermarkets.

That's according to a criminologist from Leicester University who says customers are committing payment fraud when they scan expensive items through as cheaper ones.

Payment fraud cost Australian retailers more than $400 million last year alone.

Adrian Beck told Rachel Smalley a faceless checkout makes it easier for people to justify their stealing.

"If somebody finds out that we haven't scanned an item at a self serving checkout, we're very good at saying we're terribly sorry and asking if we got it wrong, after all they are making us use this technology."