Given the implications of behavioral inhibition (BI) on social anxiety and depression, several cost-effective methods have been developed to detect this trait. However, there is no instrument for obtaining a systematic measurement of BI that uses the reports of mental health professionals. The present study aims to explore the psychometric properties of the Behavioral Inhibition Observation System (BIOS), a brief tool enabling clinicians to provide a quick measure of BI. Parents and teachers of 361 preschool children provided measures of BI and psychopathology. Clinicians completed the BIOS after an individual meeting with every child. Seventy-four randomly selected children were exposed to standardized observation. Two researchers completed the BIOS after standardized observation. The results show that the BIOS is structured in one dimension that explains 60 % of the total variance. It shows good internal consistency (Cronbach’s Alpha = .88) and good test-retest reliability. The BIOS scores moderately converge with observational measures of BI and adequately distinguish constructs not related to BI (such as aggressiveness, disruptive behavior, or peer conflict). The results support that the BIOS, an 8-item scale that takes 3 min to complete, is valid and reliable for capturing a clinician’s measure of BI. The BIOS may help to detect temperamental disposition to social anxiety.
