Final answer:
Masters and Johnson's human sexual response research is criticized for having a non-diverse participant pool and the potential influences of a laboratory setting on the sexual responses recorded, which may challenge the generalizability of their findings.
Step-by-step explanation:
Two criticisms of Masters and Johnson's human sexual response research include the lack of diversity in their participant pool and the potential influence of laboratory settings on participants' behavior. Firstly, their sample was not diverse and may not represent the sexual behavior of the broader population. Secondly, the artificial laboratory setting could have influenced the behavior and responses of the participants, casting doubt on whether the findings can be generalized to natural sexual experiences. Despite these criticisms, their work remains a significant contribution to the field of sexual health.