ABSTRACT
Contents Introduction................................................................................................ 182
The Mystery of Delusions .................................................................... 183 Should a Function for Delusions Be Considered? ............................ 185
The Selection Pressure: Severe Social Failure ....................................... 186 The Adaptations: Vigilance and Exploitative Deception ..................... 188
Increased Vigilance .............................................................................. 188 Signaling and Deception: General Theory ....................................... 189 Human Social Parasites ....................................................................... 191 Domains of Deception ......................................................................... 192
Social Exchange ................................................................................ 192 Defense .............................................................................................. 192 Mating ............................................................................................... 193
Delusions as Exploitative Deception ...................................................... 193 Mental Illness as Adaptation .............................................................. 193 Delusional Disorder ............................................................................. 193 Paranoia as Increased Vigilance ......................................................... 194 Delusions as Adaptations for Exploitative Deception ..................... 195
Social Problems Cause Delusions ........................................................... 198 Psychiatric Populations ........................................................................ 198 Longitudinal Population Surveys ......................................................200 Immigrants and Refugees ................................................................... 201 Low Socioeconomic Status .................................................................. 202
Delusions “Work” in Small-Scale Societies ...........................................203 Social Benets and the Remission of Delusions ...................................206 Detecting Exploitative Deception ...........................................................206 Delusions with Other Symptoms ............................................................208 Conclusion ..................................................................................................209 Acknowledgments ..................................................................................... 210 References ................................................................................................... 210
Introduction Strategic analysis has yielded several surprising insights into animal behavior. Costly and seemingly harmful traits, such as the large, cumbersome tail of the peacock, or the exhausting bouts of roaring by red deer, are now understood to credibly signal aspects of quality to potential mates. Yet psychiatry, despite its focus on costly and therefore seemingly harmful behavior, has made almost no use of this powerful conceptual tool (the work of Nesse and a few others being notable exceptions). Seen through a strategic lens, it is conceivable that some behaviors currently thought to indicate madness might have a method to them, an idea that appears, surprisingly, in the early work one of psychiatry’s harshest critics, Thomas Szasz.
