Learning by social and material reward in children with ASD and children with ADHD:
A neurophysiological study

Attention Deficit Hyperactivity Disorder (ADHD) and Autism Spectrum Disorder
(ASD) are relatively prevalent neuropsychiatric developmental disorders that
cause impairments in several life domains, including the academic and social
functioning. Even though in clinical practice there is much overlap between the
disorders, scientific explanatory models assume that these disorders differ in
their sensitivity to social and material reward.
Several models of ADHD hypothesise a central motivation deficit, which
can explain the attentional problems and the hyperactive, chaotic and impulsive
behaviour of children with ADHD. In research this motivational deficit is
apparent in a preference for immediate over delayed rewards. Therefore, adding
an adequate reward and penalty schedule has a stronger positive effect in these
children compared to healthy controls, i.e. they appear more dependent on
external rewards.
Even though the present models of ASD hypothesise a general deficit in
empathy to explain the social, emotional, and communication problems, recently
reward sensitivity gained more interest. The social motivation theory of ASD
hypothesises that individuals with ASD are less sensitive to social reward,
which causes them to appreciate and approach social stimuli (such as facial
expressions or social play) to a lesser extent. However, only little is known
about reward sensitivity in ASD. Some studies suggest intact material reward
sensitivity, but a reduced social reward sensitivity, whereas others suggest a
generally reduced reward sensitivity.

The main objective of this study is to determine how children with ADHD and ASD
differ from each other in learning from social and material reward. The
secondary objectives are: 1) To determine how predictability of the rewards
influences learning from social and material reward in these disorders; 2) To
determine which neurophysiological mechanisms underlie learning from social and
material reward in these disorders?

Four factorial design: mixed between-subject (group: ADHD, ASD, control group)
and repeated measures design (reward type: material, social, no reward;
learning phase: first section, second section; reward predictability:
consequent, inconsequent).

The investigator will meet the child and parent/caregiver once for an intake
(45 min) and once for the experiment (3 hours). During the intake, a short
intelligence test is assessed in the child and the parent completes behavioural
questionnaires. During the experiment, learning tasks are assessed in the child
with material, social and no reward, and two short social cognition tests (3
hours). During the experiment the child wears EEG and ECG equipment (a cap and
sticky electrodes). The physiological measurements are not painful and bear no
risks for the child. In the meantime the parent completes additional behavioral
questionnaires (45 min) and gives the social reward (play with the child for
max. 30 min). The assessments will require a certain amount of concentration
from which the child and parent can recover after short breaks. The risks of
this study are negligible and the burden can be considered minimal. Patients
will have no direct benefit from the study.