Although behaviorists emphasize environment they almost totally deny the influence of biological variables on development.
Step-by-step explanation:
The idea of development isn't limited to the entity that is developing. The development of a subject is caused due to the contribution of a number of factors. One such important factor is the environment that the subject is living in.
It is argued that when behaviorists study development, they take into consideration what impact the environment makes on the development of the subject but leave out on studying the impact of biological factors present in the same environment.