Chick neuro-economics: profitability, risk and competition
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1
Hokkaido University, Department of Biology, Faculty of Science,, Japan
Every day, we make some decisions. You may decide to smoke, while you are explicitly told that the delight leads to lung cancer in the long run. You may save money for post-retirement pension, while you do not know whether you will survive long enough. Decisions are thus fundamentally “irrational,” since they inevitably involve something that we cannot foresee. In this talk, I will show you some studies on decision making in newly hatched domestic chicks, particularly on the hidden reasons of their apparent impulsiveness in terms of ecology and evolution. Attention will be paid also to the neuronal representatives of reward values (proximity and amount) in the ventral striatum including nucleus accumbens, and the neuromodulatory actions of 5-HT / dopamine in these regions.
Only the fittest survive, as has been repeatedly argued since Charles Darwin. Evolutionary thinking often obsessively forces us to speak that optimality is the rule, and to assume that a reliable measure of goodness (or a currency) is uniquely given. The idea of our decisions being controlled by the optimality principle have also been the norm since a theoretical biologist Eric L. Charnov has put it more than three decades ago. He applied a simple mathematics to the issue of foraging decisions, and showed that profitability is the key. If a forager animal gains “e” (for energetic gain) at the expense of “h” (for handling time), value of the food item is uniquely given by the ratio “e/h” that is the profitability. In the world where encounter with food items are unpredictable, optimal animals should simply be short-minded, taking only the immediate consequence into account. Best policy is to make the immediate gain the largest. Actually, chicks do this way, and it is one of the major reasons why they are supposed to behave impulsively. A series of localized brain lesion experiments revealed that decision factors (such as proximity, amount and cost) are separately represented in the brain systems that involve basal ganglia. Some of these behavioral parameters are substantiated by their neural substrates.
Another major reason is competition. As food resource is scarce in the wild, optimal decision makers must go for the food proximity in competitive foraging with conspecifics. Actually, when trained in a group, chicks become more impulsive in choices between an immediate/small food and a delayed/large alternative. Accordingly, neuronal codes of reward values are subject to acute modulation in competition, leading to lasting biases of the neuronal representations in favor of the food proximity. Competition inevitably a risk, but the risk alone failed to cause the impulsive choices at the individual time scale. However, comparisons of sympatric species of closely related tits (genus Poecile and Parus) revealed divergent risk sensitivity, which were linked to the diet menu diversification. Competition could causes, at least at the evolutionary time scale, animals to change their strategies to risks. In future, neural differentiations underlying the evolution of impulsiveness, diet menu and risk sensitivity should be searched for in the neuromodulatory systems acting on the basal ganglia.
Keywords:
Decision Making,
Dopamine,
impulsiveness,
medial striatum,
Nucleus Accumbens,
optimal foraging,
patch use behavior,
Serotonin
Conference:
Tenth International Congress of Neuroethology, College Park. Maryland USA, United States, 5 Aug - 10 Aug, 2012.
Presentation Type:
Plenary Address (including special lectures) (Note, these individuals have already been invited)
Topic:
Learning, Memory and Behavioral Plasticity
Citation:
Matsushima
T
(2012). Chick neuro-economics: profitability, risk and competition.
Conference Abstract:
Tenth International Congress of Neuroethology.
doi: 10.3389/conf.fnbeh.2012.27.00405
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Received:
02 May 2012;
Published Online:
07 Jul 2012.
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Correspondence:
Prof. Toshiya Matsushima, Hokkaido University, Department of Biology, Faculty of Science,, Sapporo, Hokkaido, 060-0810, Japan, matsushimatoshiya@gmail.com