This prospective, non-randomized, open-label study is performed to assess the effects of adjunctive SI in the family-based treatment program of children with developmental delay (DD). The study subjects are children with DD who attended an early intervention (EI) program at Kaohsiung Chang Gung Memorial Hospital, which is the largest general hospital in the Southern Taiwan. Each participating child undergo a joint assessment by a pediatrician, a rehabilitation doctor, a child psychiatrist, a speech therapist, a physical therapist, an occupational therapist, and a social worker. Once the diagnosis of developmental delay is confirmed, the child will be scheduled for prescribed family-based early intervention in the same hospital. Children (between 2 to 4 years old) who attend the program will be enrolled in this study. Informed consent will be obtained from the children and their primary caregivers after they received a complete description of the study. The participants are categorized into three different groups based on their intervention method. The choice of intervention method will be according to the willingness and expedience of the children's caregivers.