How does prayer change the person who prays? In this article, we report on a randomized controlled trial developed to test an ethnographic hypothesis. Our results suggest that prayer which uses the imagination—the kind of prayer practiced in many U.S. evangelical congregations—cultivates the inner senses, and that this cultivation has consequences. Mental imagery grows sharper. Inner experience seems more significant to the person praying. Feelings and sensations grow more intense. The person praying reports more unusual sensory experience and more unusual and more intense spiritual experience. In this work we explain in part why inner sense cultivation is found in so many spiritual traditions, and we illustrate the way spiritual practice affects spiritual experience. We contribute to the anthropology of religion by presenting an attentional learning theory of prayer.