The children were entirely involved in this intervention program at home, with 20 minutes each time, 4 times a week for 8 weeks. The caregiver was required to perform the interactive picture book specified by the AR home training modules. During the process, the caregivers could directly contact the researcher by telephone and instant messaging for solving problems that occur during the interaction. The researcher and the caregiver consistently met once every two weeks. On the day of the meeting, the caregiver needs to prepare at least ten minutes of interactive video to discuss with the researcher. The researcher not only provides suggestions for caregiver interaction skills based on the video, in order to facilitate the child's interaction. The interaction strategies were also revised according to the interaction ability and special behavior problems of individual children.

The AR system was developed using a Vuforia Engine Package for Unity (PTC Inc, San Diego, CA), which enabled to create an application for children to view a storybook in their own homes. The children and caregivers could view eight scenarios (receiving a praise, broken toys, waiting in line at the playground, getting a vaccination, waiting for watching a video, hitting someone in an accident, grabbing a toy, understanding another person's feelings) and learn strategies for emotional events reflected in the tablet (Figure 1). This AR application supports a tablet size of 10.4 inches and is equipped with a Samsung Galaxy Tab A7.

The Vineland Adaptive Behavior Scales-Third Edition (VABS-3) comprises four domains, that is, communication, daily living skills, socialization and motor skills, for assessing adaptive functioning in children aged 3 to 12 years old. The raw score in each domain and total raw score are converted to an age-equivalent score. The domain scores are also expressed as standard scores with a mean of 100 and standard deviation of 15. The range for each subscale is from 20 to 140. The subscales are summed to compute a total score, ranging from 80 to 560. The higher the scores are, the better adaptive functioning the children achieve.

The Functional Emotional Assessment Scale (FEAS; Greenspan et al., 2001) is based on six functional developmental levels of the developmental individual-difference relationship-based model and divided into two parts that (1) examine the children's development and (2) assess the parenting skills. All parents in the study were asked to record their parent-child activities as 15-minute videos. All videos were coded using random numbers to hide the research information (e.g. groups and test time). Two videos (pre- and post-test) were reviewed for each child. Using the Chinese version of the Scoring Form translated by Liao et al. (2014; intraclass correlation coefficient = 0.85), each item of the FEAS was rated as 0, 1 or 2. Higher raw scores represent better functions and skills. The total score is summed and ranges from 0 to 80.