Personal experiences with human development and family relationships are ubiquitous, and produce a form of knowledge that deceptively feels absolutely certain. But personal experience is often irrelevant to professional expertise in HDFS because it is necessarily quite narrow, and it is potentially distorted through normal human biases of perception and reasoning. These biases include tendencies toward pattern-seeking and meaning-making, selective attention, illusion of superiority, the vividness effect, false memory, and confirmation bias, among others. Conspiracy theory thinking makes it difficult to challenge these cognitive biases. The ubiquity of personal experience with development and relationships means the discipline of HDFS is especially vulnerable to problems with false authority.