Emotional facial expression paradigms of adults have been very used in the literature; however, studies with baby's emotional faces are very few.

To study the psychometric validity and reliability of a series of basic emotions faces of babies stimuli.

We used 72 photographs of 12 baby faces (6–12 months), both sex and different ethnic groups, expressing basic emotions (happiness, sadness, fear, anger, surprise and neutral) elicited in the laboratory by pre-task defined. A total of 119 subjects of both sexes (63% women) in different age groups (18–65 years) and ethnicities, were invited to evaluate the facial emotional stimuli presented by the computer program SuperLab. They should choose the emotion represented by the photograph. Furthermore, 31 subjects were randomly selected to perform a test-retest assessment after an interval of 20 days.

It was observed that 35 stimuli presented hit rate exceeding 70% and 11 between 60% and 50%. The facial emotion of happiness was the most easily recognized, while fear was associated with the lower success rates. Only seven stimuli presented a hit rate lower than 20% (fear). All stimuli, except for one, showed a good reliability test/retest (McNemar test > 0.05).

The study offers a series of baby emotional facial stimuli with good validity and reliability for research setting. However, the 30% of stimuli without satisfactory success rate may be problems with stimuli or stimulating task, as it becomes difficult to distinguish the emotion face on the baby.

The authors have not supplied their declaration of competing interest.