Successful tutoring depends in part on child tutors' ability to recognise and interpret accurately signals of misunderstanding by their tutees. Age- and gender-related differences were investigated in a study which exposed 80 children to a video-recorded episode involving a target child receiving ambiguous instructions in her attempts to move a model car along a designated route on a playmat roadway from one destination to another. The results showed that explicit, general and facial modes of displaying puzzlement by the target child were judged as equally powerful expressions of degree of puzzlement, but 8-10 year olds judged the target child as significantly more puzzled than did 7 year olds. Older children were also more likely to attribute the puzzlement of the target child to the ambiguous instructions than to her verbal or facial expression of puzzlement. Girls were generally more accurate than boys in judging facial expressions and less likely than boys to give wrong or alternatively ambiguous responses when given the opportunity to correct the video-recorded ambiguous instructions. The results throw some light on the developing sensitivities of boys and girls in recognising and attributing failures of understanding by other children.