Objective To explore the characteristics of social behaviors in toddlers with high-risk of autism spectrum disorder (HR-ASD),and the correlation to the severity of ASD symptoms.Method 32 high-risk ASD toddlers,aged from 12 months to 24 months,and 34 typical developmental (TD) infants/toddlers,aged from 6 months to 24 months,were recruited.Behavioral video of the Still-Face Paradigm (SFP) was used to measure the frequencies and duration of social behaviors,including non-social smiling,protest,eye contact,social smiling and social positive engagement,during the mother-infant interaction and the still face.Autism Diagnostic Observation Scale was used to evaluate severity of clinical symptoms in high-risk ASD toddler.Gesell Development Scale was used to assess the developmental level of the two groups.Independent-sample t test was used to compare the differences of social behaviors between two groups.Pearson correlation analysis was used to analyze the correlation between the social behaviors of high-risk ASD and the age,the developmental level and the severity of ASD symptoms.Binary logistic regression was used to analyze the power of discrimination of social behaviors between HR-ASD and TD.Results During mother-infant interaction,compared with TD group,HR-ASD had significantly shorter duration ((19.8±23.4) s vs.(61.5±34.0) s,t=-5.75,P＜0.01;(6.5±9.3) s vs.(29.0±25.2) s,t=-4.73,P＜0.01;(3.0±8.8) s vs.(13.2±23.1) s,t=-2.34,P=0.02) and lower frequencies (t=-6.62、-3.03、-2.74,all P＜0.01) of eye contact,social smiling and social positive engagement.During the still face,compared with TD group,HR-ASD had significantly shorter duration (t=-3.32,P＜0.01;t=-2.59,P=0.01) and lower frequencies (t=-6.13、-3.48,all P＜0.01) of eye contact and social positive engagement.According to Pearson correlation analysis,during the still face,in HR-ASD group,the duration of eye contact and social positive engagement had significantly negative influence on the score of the language and communication in ADOS (r=-0.49、-0.52,all P＜0.01);The duration and frequencies of eye contact and social positive engagement had significantly negative influence on the score of mutually social interaction in ADOS (r=-0.57,P＜0.01;r=-0.49,P＜0.01;r=-0.74,P＜0.01;r=-0.44,P=0.01);The duration of eye contact and social positive engagement had significantly negative influence on the score of the playing in ADOS (r=-0.43,P=0.01;r=-0.45,P=0.01).According to binary logistic regression,the duration of social smiling during the still face and the frequencies of eye contact during mother-infant interaction could distinguish between HR-ASD and TD (OR=1.36,95％CI:1.08-1.71,P=0.01;OR=5.99,95％CI:1.15-31.14,P=0.03).Conclusion HR-ASD hasthe lower levels of eye contact,social smiling and social positive engagement,which may suggestthe severity of ASD core symptoms.The duration of social smiling during the still face and the frequencies of eye contact during mother-infant interaction may possiblyfigure out theHR-ASD and could be further developed as a predictablebehavioral maker.

Objective To explore the characteristics of social behaviors in toddlers with high-risk of autism spectrum disorder (HR-ASD),and the correlation to the severity of ASD symptoms.Method 32 high-risk ASD toddlers,aged from 12 months to 24 months,and 34 typical developmental (TD) infants/toddlers,aged from 6 months to 24 months,were recruited.Behavioral video of the Still-Face Paradigm (SFP) was used to measure the frequencies and duration of social behaviors,including non-social smiling,protest,eye contact,social smiling and social positive engagement,during the mother-infant interaction and the still face.Autism Diagnostic Observation Scale was used to evaluate severity of clinical symptoms in high-risk ASD toddler.Gesell Development Scale was used to assess the developmental level of the two groups.Independent-sample t test was used to compare the differences of social behaviors between two groups.Pearson correlation analysis was used to analyze the correlation between the social behaviors of high-risk ASD and the age,the developmental level and the severity of ASD symptoms.Binary logistic regression was used to analyze the power of discrimination of social behaviors between HR-ASD and TD.Results During mother-infant interaction,compared with TD group,HR-ASD had significantly shorter duration ((19.8±23.4) s vs.(61.5±34.0) s,t=-5.75,P＜0.01;(6.5±9.3) s vs.(29.0±25.2) s,t=-4.73,P＜0.01;(3.0±8.8) s vs.(13.2±23.1) s,t=-2.34,P=0.02) and lower frequencies (t=-6.62、-3.03、-2.74,all P＜0.01) of eye contact,social smiling and social positive engagement.During the still face,compared with TD group,HR-ASD had significantly shorter duration (t=-3.32,P＜0.01;t=-2.59,P=0.01) and lower frequencies (t=-6.13、-3.48,all P＜0.01) of eye contact and social positive engagement.According to Pearson correlation analysis,during the still face,in HR-ASD group,the duration of eye contact and social positive engagement had significantly negative influence on the score of the language and communication in ADOS (r=-0.49、-0.52,all P＜0.01);The duration and frequencies of eye contact and social positive engagement had significantly negative influence on the score of mutually social interaction in ADOS (r=-0.57,P＜0.01;r=-0.49,P＜0.01;r=-0.74,P＜0.01;r=-0.44,P=0.01);The duration of eye contact and social positive engagement had significantly negative influence on the score of the playing in ADOS (r=-0.43,P=0.01;r=-0.45,P=0.01).According to binary logistic regression,the duration of social smiling during the still face and the frequencies of eye contact during mother-infant interaction could distinguish between HR-ASD and TD (OR=1.36,95％CI:1.08-1.71,P=0.01;OR=5.99,95％CI:1.15-31.14,P=0.03).Conclusion HR-ASD hasthe lower levels of eye contact,social smiling and social positive engagement,which may suggestthe severity of ASD core symptoms.The duration of social smiling during the still face and the frequencies of eye contact during mother-infant interaction may possiblyfigure out theHR-ASD and could be further developed as a predictablebehavioral maker.