According to the Bayley mental scale, by of age, the infant should be able to inhibit behavior when commanded to do so, imitate words the examiner says, and respond to simple requests.

12 months.

Explanation:

Bayley mental scale or (in full) Bayley Scales of Infant Development is a is a test used for the measurement of cognitive test and for the measurement of the communication subtest, that is to say that the Bayley Scales of Infant Development is been used for the measurement of mental development in babies that falls between the ages of 1 month old and 42 months old. Bayley Scales of Infant Development was proposed in the year 1965 by a someone named as Nancy Bayley.

According to the scale, a 12 months old baby should be able to inhibit behavior when commanded to do so.

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