Attention has been shown to modulate the amplitude
of the mismatch negativity (MMN) elicited by a small deviation
in auditory stimuli in adults. The present study examined
the effects of attention and deviant size on MMN amplitude
in children. Children and adults were presented with sequences
of tones containing standards (1000 Hz) and three deviants
varying in degree of deviance from the standard (1050,
1200, and 1500 Hz). Tones were presented in three conditions:
(1) while participants ignored them; (2) while participants
listened to them and responded to all three deviants; and
(3) while participants again ignored them. We found that
the MMNs elicited by the hard deviant (1050 Hz) were larger
when the children were actively discriminating the stimuli
than when they were ignoring them. However, the MMNs elicited
by the easy and medium deviants (1500 and 1200 Hz, respectively)
in the children and by all three deviants in the adults
were not affected by attention.