They used a test called DAYC-2.
He scored 81% delay in receptive. From the report:
In the area of receptive language, J demonstrated solid skills to 3 months with a scattering of skills to 12 months according to the Rossetti Infant-Toddler Language Scale. According to parent report and observation, J responds to sounds other than voices, responds to “no” half of the time, attends to pictures, performs a routine activity upon verbal request, and follows simple commands occasionally (with environmental cues and within familiar contexts). According to observation J responds to a speaker very inconsistently, does not maintain attention to a speaker, and looks at the person calling his name (two times out of ten opportunities across three people, during the evaluation – the two times were in response to his mother calling him). Parent also reported the following emerging/inconsistent skills: discriminates between firm and friendly voices, responds to “where____?” questions (rare), and waves in response to “bye-bye”. J had never been observed to cry in response to an angry voice, recognize family members’ names, respond to “no” most of the time, attend to new words, look at familiar people and objects when named, gestures or vocalize in response to verbal requests, participate in speech routine games or identify any body parts on himself. J does not respond to requests to say words, enjoy finger plays, respond to give me commands (without gestures), or maintain attention to picture when engaged in adult-led book interactions.
According to the DAYC-2, J demonstrated a developmental level of 7 months of age as he demonstrated only emerging skills in the following: briefly stopping activity when his name is called, responding with appropriate gesture to the language “up”, “bye-bye” and other routine language, following simple commands (only occasionally and only familiar commands or within routines) and responding to “where ___?” questions (very limited). Therefore, he did not receive credit for these skills.