Premature responses, total trials, and reaction time were differentially affected
by sex, reinforcer volume, and methylphenidate (MPH) dose. Asterisks (*)
denote significant differences between sexes (p <
0.05). Daggers (†) represent differences within-subjects
(p < 0.05). (A) Males and females
showed similar increases in premature responding for a 30 μL water
reinforcer. (B) Females, but not males showed increased premature
responding in response to methylphenidate. (C) Females had a
tendency to initiate more trials than males, although there were no differences
at higher reinforcer volumes and (D) was not altered by
methylphenidate. (E) There were no sex differences in reaction time
across reinforcer volumes or (F) methylphenidate doses. Although there was a
main effect of methylphenidate, the interaction with sex, in which females were
more sensitive to methylphenidate, did not reach statistical significance
(p = 0.056). Data are presented as means ±
SEM, and are collapsed across MPH dose (panels A, C, E) or Reinforcer Volume (B,
D, F) measure.