Public policy decisions concerning embryos and fetuses tend to lack reasoned argument on their moral status. While agreement on personhood is elusive, this concept has unquestioned moral relevance. A stipulated usage of the term, the psychic sense of 'person', applies to early human prenatal life and encompasses morally relevant aspects of personhood. A 'person' in the psychic sense has a minimal psychology, defined as the capacity to retain experiences, which may be nonconscious, through physiological analogs of memory; and the potential to become a person in the full sense. Psychic personhood merits attribution of moral personhood because the experience of a 'person' in the psychic sense has continuity with the experience of a full person; and this experience begins to determine the development of the personal psychological characteristics of that individual. Psychic personhood is a rationally defensible boundary for invasive research involving human embryos and fetuses. Lacking precise empirical knowledge, policy makers could attribute psychic personhood at the time of earliest brainstem activity, that is, during the seventh week of fetal development.