This document describes a new approach to machine learning that harnesses the wisdom of crowds to develop predictive models of behavioral outcomes. The approach uses a web platform where users answer questions to predict an outcome (like electricity usage or BMI) and also generate new questions. As more users contribute data by answering questions, models are developed that can better predict outcomes based on the question responses. Two experiments accurately predicted monthly electricity usage and BMI based on models developed from questions crowdsourced by users. This novel approach may lead to new insights into causal factors of behaviors.