Behavior Coding
The experimental tasks were coded for four behavioral measures: success,
adult assistance, hand actions, and time to plan and execute the task.
Each behavior measure was scored by two coders to establish interrater
reliability for 30% of the dataset. Interrater correlations were
> 0.85 for all the measures (Success = 1, Assistance =
0.87, Hand actions = 0.88 to 0.96, Planning time = 0.92, Execution time
= 0.85).
Success : Success was defined as the child opening the lid of the
box and taking the toy out. If after opening the lid, children used
other strategies such as vigorously shaking the box, knocking over the
box, or dumping the contents onto the table, it was considered
successful. Additionally, if children required partial assistance from
the adult experimenter (see definition below) to retrieve the toy, it
was scored as success. We are reporting on the percentage of children in
the DS and TD group who succeeded in the experimental tasks.
Adult Assistance : Adult assistance was defined as the physical
help provided by the experimenter to retrieve the toy from the box.
Assistance was scored as 0 (no assistance) if the child independently
retrieved the toy from the box, 1 (partial assistance) if the child
required help from the experimenter to stabilize the box while they
opened the lid and/or took the toy out of the box, and 2 (total
assistance) if the child was unable to complete the task on their own
and required help to open the lid and take the toy out. We are reporting
on the percentage of children in the DS and TD group who required no,
partial, and total assistance for the three tasks.
Hand actions : Child’s use of hands was scored as unimanual if
they used only one hand (right or left) and bimanual if they used both
hands while completing the task. Bimanual actions were further
categorized as symmetrical or asymmetrical. Symmetrical bimanual actions
indicated using two hands to perform a same action, e.g., opening the
lid of a box with both right and left hand. Asymmetrical bimanual
actions indicated using two hands to perform different actions, e.g.,
holding the box with one hand and opening the lid with other. We are
reporting on the total frequency of unimanual, symmetric bimanual, and
asymmetric bimanual actions for the experimental tasks.
Planning and execution time : Planning time was the time required
to plan actions and was scored as the time taken by the child to make
first manual contact with the box after the experimenter placed the box
on the table. Execution time was the time required to complete the task
and was defined as the time taken to open the lid of the box after
making first manual contact with the box. Execution time was not scored
for children who were unsuccessful in opening the lid and/or required
total assistance. We did not consider the time taken to take the toy out
of the box within the execution time as there was lot of variability in
the strategies used to take the toy out of the box. For example, some
children quickly dumped the toy on the table after opening the lid vs
others took time to carefully scoop the toy out using their fingers. We
are reporting on the planning and execution time in seconds for the
three tasks and the total time.