Natural Rationality | decision-making in the economy of nature


Fairness and Schizophrenia in the Ultimatum

For the first time, a study look at schizophrenic patient behavior in the Ultimatum Game. Other studies of schizophrenic choice behavior revealed that they have difficulty in decisions under ambiguity and uncertainty (Lee et al, 2007), have a slight preference for immediate over long-term rewards, (Heerey et al, 2007), exhibit "strategic stiffness" (sticking to a strategy in sequential decision-making without integrating the outcomes of past choices; Kim et al, 2007), perform worse in the Iowa Gambling Task (Sevy et al. 2007)

A research team from Israel run a Ultimatum experiment with schizophrenic subjects (plus two control group, one depressive, one non-clinical). They had to split 20 New Israeli Shekels (NIS) (about 5 US$). Although schizophrenic patients' Responder behavior was not different from control group, their Proposer behavior was different: they tended to be less strategic.

With respect to offer level, results fall into three categories, fair (10 NIS), unfair (less than 10 NIS), and hyper-fair (more than 10 NIS). Schizophrenic patients tended to make less 'unfair' offer, and more 'hyper-fair' offer. Men were more generous than women.

According to the authors,

for schizophrenic Proposers, the possibility of dividing the money evenly was as reasonable as for healthy Proposers, whereas the option of being hyper-fair appears to be as reasonable as being unfair, in contrast to the pattern for healthy Proposers.
Agay et al. also studied the distribution of Proposers types according to their pattern of sequential decisions (how their second offer compared to their first). They identified three types:
  1. "‘Strong-strategic’ Proposers are those who adjusted their 2nd offer according to the response to their 1st offer, that is, raised their 2nd offer after their 1st one was rejected, or lowered their 2nd offer after their 1st offer was accepted.
  2. Weak-strategic’ Proposers are those who perseverated, that is, their 2nd offer was the same as their 1st offer.
  3. Finally, ‘non-strategic’ Proposers are those who unreasonably reduced their offer after a rejection, or raised their offer after an acceptance."
20% of the schizoprenic group are non-strategic, while none of the healthy subjects are non-strategic.

the highest proportion of non-strategic Proposers is in the schizophrenic group
The authors do not offer much explication for these results:

In the present framework, schizophrenic patients seemed to deal with the cognition-emotion conflict described in the fMRI study of Sanfey et al. (2003) [NOTE: the authors of the first neuroeconomics Ultimatum study] in a manner similar to that of healthy controls. However, it is important to note that the low proportion of rejections throughout the whole experiment makes this conclusion questionable.
Another study, however, shows that "siblings of patients with schizophrenia rejected unfair offers more often compared to control participants." (van ’t Wout et al, 2006, chap. 12), thus suggesting that Responder behavior might be, after all, different in patient with a genetic liability to schizophrenia. Yet another unresolved issue !

Related Posts

  • Agay, N., Kron, S., Carmel, Z., Mendlovic, S., & Levkovitz, Y. Ultimatum bargaining behavior of people affected by schizophrenia. Psychiatry Research, In Press, Corrected Proof.
  • Hamann, J., Cohen, R., Leucht, S., Busch, R., & Kissling, W. (2007). Shared decision making and long-term outcome in schizophrenia treatment. The Journal of clinical psychiatry, 68(7), 992-7.
  • Heerey, E. A., Robinson, B. M., McMahon, R. P., & Gold, J. M. (2007). Delay discounting in schizophrenia. Cognitive neuropsychiatry, 12(3), 213-21.
  • Hyojin Kim, Daeyeol Lee, Shin, Y., & Jeanyung Chey. (2007). Impaired strategic decision making in schizophrenia. Brain Res.
  • Lee, Y., Kim, Y., Seo, E., Park, O., Jeong, S., Kim, S. H., et al. (2007). Dissociation of emotional decision-making from cognitive decision-making in chronic schizophrenia. Psychiatry research, 152(2-3), 113-20.
  • Mascha van ’t Wout, Ahmet Akdeniz, Rene S. Kahn, Andre Aleman. Vulnerability for schizophrenia and goal-directed behavior: the Ultimatum Game in relatives of patients with schizophrenia. (manuscript), from The nature of emotional abnormalities in schizophrenia: Evidence from patients and high-risk individuals / Mascha van 't Wout, 2006, Proefschrift Universiteit Utrecht.
  • McKay, R., Langdon, R., & Coltheart, M. (2007). Jumping to delusions? Paranoia, probabilistic reasoning, and need for closure. Cognitive neuropsychiatry, 12(4), 362-76.
  • Sevy, S., Burdick, K. E., Visweswaraiah, H., Abdelmessih, S., Lukin, M., Yechiam, E., et al. (2007). Iowa Gambling Task in schizophrenia: A review and new data in patients with schizophrenia and co-occurring cannabis use disorders. Schizophrenia Research, 92(1-3), 74-84.