Smiling does not necessarily indicate that a person is happy, according to a study.
Researchers from the University of Sussex in the UK show this is not always the case.
The way people often behave during one-to-one Human-Computer-Interaction (HCI) is as if they were socially engaged, researchers said.
After the quiz, the participants were asked to rate their subjective experience using a range of 12 emotions including 'bored', 'interested' and 'frustrated'.
"However, Behavioural Ecology Theory suggests that all smiles are tools used in social interactions; that theory claims that cheerfulness is neither necessary nor sufficient for smiling," Witchel said.
"Our study showed that in these Human-Computer Interaction experiments, smiling is not driven by happiness; it is associated with subjective engagement, which acts like a social fuel for smiling, even when socializing with a computer on your own," he said.
Statistically, the emotion that was most associated with smiling was 'engagement' rather than 'happiness' or 'frustration'.
Participants did not tend to smile during the period when they were trying to figure out the answers, researchers said.
"This behavior could be explained by self-ratings of engagement, rather than by ratings of happiness or frustration," he said.