(except in baseline and reversal probes), table,
chairs, and a board that displayed the game
choices for the choice pages. The board hung on
a wall near the toy shelf and activity schedule.
Measurement
During all sessions, independent observers
used a 20-s momentary time-sampling proce-
dure to estimate the duration of peer engage-
ment and to record prompts. Dyads were scored
at each interval as being engaged, prompted, or
unengaged. Dyads were scored as engaged if
both participants were taking turns, using the
game materials in the manner in which they
were designed, cleaning up game materials,
setting up game materials, obtaining or putting
the game on the shelf, choosing a picture of the
game from the choice board, initiating play
(either independently or by following the
appropriate script without additional prompt-
ing from an instructor), verbally interacting
with a peer, turning the page of the activity
schedule, attending to the picture depicted on
the activity schedule, or walking between the
schedule, game shelf, choice board, and table
without prompting. An interval was scored as
prompted when the instructor had his or her
hands on one or both participants or when the
instructor was shadowing one or both partici-
pants within a distance less than 1.5 m.
Participants were scored as unengaged if they
were engaged in behaviors other than those
specified for engagement and were not being
prompted by an instructor.
Interobserver agreement data were obtained
in at least 30% of the sessions across all
conditions. For an interval to count as an
agreement, both observers had to agree on
which game was being played; if the partici-
pants were engaged, prompted, or unengaged;
and if they were engaged in the activity depicted
on the schedule in each interval. Mean
agreement was 91% (range, 84% to 100%)
for Brady and David, 88% (range, 63% to
100%) for Ali and Dillon, and 92% (range,
71% to 100%) for Nathan and Jackson.
Procedure
Sessions lasted 20 min during baseline and
reversal probe phases. In all other phases,
sessions ended when all pages of the joint
schedule were completed and varied in length,
depending on how long it took to complete
each game. Each session began with the children
standing in front of the shelf containing the
relevant games and when the data collector gave
the instruction, ‘‘These are the games you can
play with. Go play.’’ Six interactive games were
concurrently available, which we chose due to
availability, having a clear beginning and end,
and allowing two people to play at the same
time (e.g., Don’t Break the Ice; Hungry,
Hungry Hippos; Don’t Spill the Beans; Croc-
odile Dentist). An adult instructor taught each
child how to play appropriately with all of the
games, and each participant demonstrated
proficiency with all of the games prior to the
beginning of the research. Children were
considered proficient at the games when they
could play and complete the game with no
prompts to take turns, follow the rules of the
game, and set up and clean up the game.
Baseline and reversal probe. The joint activity
schedule was not present. Inappropriate behav-
ior or attempts to interact with anyone other
than the participating peer were ignored.
Children were given the standard instruction
to play, and no additional manual or verbal
prompts were delivered. After the initial
baseline, a baseline probe with the schedule
present was conducted.
Teaching. A joint photographic activity
schedule was displayed in a three-ring binder
for each dyad. Each schedule book contained
two prechosen activity pages followed by two
choice pages (two games were designated for the
prechosen activities and the remaining four
games were used as choices). Each member of
the dyads was responsible for one choice page
and one prechosen activity page. The prechosen
activity page included a picture of the respon-
sible participant at the top and a picture of the
238 ALISON BETZ et al.