Abstract The present study investigated the acquisition of
visual simple discrimination and reversal learning sets using
intermixed discrimination training (i.e., two or more pairs of
stimuli presented in the same session) in 2-year-old typically
developing children. An additional purpose was to investigate
the effects of the procedure on the production of functional
classes. The study was a systematic replication of previous
research conducted with preschool children. Three children
participated in the study. The participants were initially exposed
to simple discrimination training with two pairs of stimuli
in separate sessions. The next phase involved intermixed
discrimination training in which the two pairs of stimuli (A
and B) were presented in the same session. After the criterion
was reached, the children were exposed to repeated reversals
with Pairs A and B. Two participants were exposed to an
adaptation of the blocked-trial procedure before being exposed
to sessions that presented the stimuli in a random sequence.
The same sequence was conducted with three additional
pairs of stimuli (C, D, and E), with the exception that all
of the participants were exposed to the procedure without the
blocked-trial procedure. The results indicated that all of the
children learned discriminations and showed decreases in the
number of sessions to reach the criterion and errors. The
blocked-trial procedure was effective in producing errorless
learning during the initial intermixed discriminations. However,
during repeated reversals, the effects of the blocked-trial
procedure were not so clear, since performance wasinfluenced by motivational and other procedural variables.
All three participants showed evidence of functional class formation
in some of the reversal phases. Functional class formation
was also influenced by the occurrence of errors and
motivational variables.