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Social-economical decision making in current and remitted major depression
- E. Pulcu, E. J. Thomas, P. D. Trotter, M. McFarquhar, G. Juhasz, B. J. Sahakian, J. F. W. Deakin, I. M. Anderson, R. Zahn, R. Elliott
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- Journal:
- Psychological Medicine / Volume 45 / Issue 6 / April 2015
- Published online by Cambridge University Press:
- 10 October 2014, pp. 1301-1313
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Background.
Prosocial emotions related to self-blame are important in guiding human altruistic decisions. These emotions are elevated in major depressive disorder (MDD), such that MDD has been associated with guilt-driven pathological hyper-altruism. However, the impact of such emotional impairments in MDD on different types of social decision-making is unknown.
Method.In order to address this issue, we investigated different kinds of altruistic behaviour (interpersonal cooperation and fund allocation, altruistic punishment and charitable donation) in 33 healthy subjects, 35 patients in full remission (unmedicated) and 24 currently depressed patients (11 on medication) using behavioural-economical paradigms.
Results.We show a significant main effect of clinical status on altruistic decisions (p = 0.04) and a significant interaction between clinical status and type of altruistic decisions (p = 0.03). More specifically, symptomatic patients defected significantly more in the Prisoner's Dilemma game (p < 0.05) and made significantly lower charitable donations, whether or not these incurred a personal cost (p < 0.05 and p < 0.01, respectively). Currently depressed patients also reported significantly higher guilt elicited by receiving unfair financial offers in the Ultimatum Game (p < 0.05).
Conclusions.Currently depressed individuals were less altruistic in both a charitable donation and an interpersonal cooperation task. Taken together, our results challenge the guilt-driven pathological hyper-altruism hypothesis in depression. There were also differences in both current and remitted patients in the relationship between altruistic behaviour and pathological self-blaming, suggesting an important role for these emotions in moral and social decision-making abnormalities in depression.
Temporal discounting in major depressive disorder
- E. Pulcu, P. D. Trotter, E. J. Thomas, M. McFarquhar, G. Juhasz, B. J. Sahakian, J. F. W. Deakin, R. Zahn, I. M. Anderson, R. Elliott
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- Journal:
- Psychological Medicine / Volume 44 / Issue 9 / July 2014
- Published online by Cambridge University Press:
- 01 November 2013, pp. 1825-1834
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Background
Major depressive disorder (MDD) is associated with abnormalities in financial reward processing. Previous research suggests that patients with MDD show reduced sensitivity to frequency of financial rewards. However, there is a lack of conclusive evidence from studies investigating the evaluation of financial rewards over time, an important aspect of reward processing that influences the way people plan long-term investments. Beck's cognitive model posits that patients with MDD hold a negative view of the future that may influence the amount of resources patients are willing to invest into their future selves.
MethodWe administered a delay discounting task to 82 participants: 29 healthy controls, 29 unmedicated participants with fully remitted MDD (rMDD) and 24 participants with current MDD (11 on medication).
ResultsPatients with current MDD, relative to remitted patients and healthy subjects, discounted large-sized future rewards at a significantly higher rate and were insensitive to changes in reward size from medium to large. There was a main effect of clinical group on discounting rates for large-sized rewards, and discounting rates for large-sized rewards correlated with severity of depressive symptoms, particularly hopelessness.
ConclusionsHigher discounting of delayed rewards in MDD seems to be state dependent and may be a reflection of depressive symptoms, specifically hopelessness. Discounting distant rewards at a higher rate means that patients are more likely to choose immediate financial options. Such impairments related to long-term investment planning may be important for understanding value-based decision making in MDD, and contribute to ongoing functional impairment.
The lack of evidence for co-adaptation in crosses between geographical races of Drosophila subobscura Coll.
- A. M. McFarquhar, Forbes W. Robertson
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- Journal:
- Genetical Research / Volume 4 / Issue 1 / February 1963
- Published online by Cambridge University Press:
- 14 April 2009, pp. 104-131
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1. The paper described an attempt to see whether differences in co-adaptation between populations of Drosophila subobscura are related to the distance between them. The mean and the variance of body-size, development time and survival were recorded on parent populations and the F1 and F2 of various crosses to test for heterosis in the F1 and decline in performance or greater variance in the F2, which might indicate the break-up of co-adapted gene arrays. Comparisons were carried out at different temperatures and on a variety of larval diets, especially sub-optimal ones in which the larvae were grown on synthetic media. A large number of wild flies were caught at sites separated by about 10 miles along a transect of southern Scotland; these comprised one series of comparisons. For more distant crosses flies were caught at sites in southern England, Denmark, Switzerland and Israel.
2. There were well-defined differences in body-size, and, to a lesser degree, development time between populations from more widely separated localities and these showed evidence of a cline, northern populations having larger body-size. The difference in size between the Scottish and Isreal populations is about 20%.
3. There was no evidence of differences in co-adaptation between populations even in crosses between populations from sites as far apart as Scotland and Israel. The F1's were always close to the mid-parent values and there was no evidence of breakdown in the F2 nor of increased variability.
4. There was hardly any evidence of gene-environment interaction either with respect to different diets or to different temperatures.
5. Records of body-size on flies caught in the wild showed that they are extremely variable, indicating great variation in larval nutrition. Under natural condition stability of growth in body-size is conspicuously lacking in this species.
6. An additional test of co-adaptation was based on the between-family variance of abdominal bristle number of intra- and inter-population matings in the two most widely separated populations. There was no evidence of greater variance in the inter-population series.
7. To test for possible differences in breeding structure, the response to inbreeding was determined for two widely separated populations of D. subobscura and a long-established cage population of D. melanogaster, on an unrestricted larval diet and also on several different kinds of sub-optimal diets. There was little or no sign of consistent differences between the species in their response to inbreeding.
8. This test revealed differences between the two species in their minimum requirements for particular nutrients. subobscura is less able than melanogaster to withstand lower levels of protein and survival is particularly reduced. On the other hand, melanogaster has a considerably higher requirement for choline. Where there are apparent differences between the species in the average effect of inbreeding, the inbreeding effect is greater on the relatively more sub-optimal diet.
9. Comparison of the performance of the immediate descendants of wild flies with those derived from the same site, but kept in the laboratory for some twenty generations, failed to show any differences on several different diets and so there was no evidence that adaptation to laboratory conditions was important.
10. The lack of evidence for co-adaptation apparently conflicts with what has been claimed for other species. Such differences are discussed.