There are some practical challenges in this approach. Groups of patients with uniform delusions tend to be small, patients often have more than one delusion, and the content can change within certain bounds over time. Moreover, a delusion’s interpersonal meaning, emotional valence, or cognitive link to personal identity can be difficult to measure but may be critical in its cognitive or physiological development. There also may be a conceptual advantage to studying patients with a variety of delusional thoughts. Regardless of thought content, memory deficits, or perceptual influences, patients with delusions are unusually willing to accept an implausible conclusion. This cognitive process that extends beyond specific thought content may itself have discrete neurobiological underpinnings.