2014-11-08 07:26:21 Osaka University.
To a human being The remuneration (reward) to take is what is required for maintenance of a life, such as money and food, and a thing indirectly connected with it.
However, probably, the joy which a student feels differs from the joy which the wealthy's person feels also, for example with the remuneration of 1 million yen.
Thus, it is predicted that "what joy is felt in consideration [ a certain ]" is subjective.
In economics, such a joy is called a "use" and "value."
People assumed modern economics to have chosen action based on subjective "use" and "value", and it considers man's action.
Then, are a "use" and "value" influenced by what kind of element? As main elements, the actual proof experiment of psychology or economics has shown that people feel value large, so that remuneration can get "a lot" "immediately" "to be sure."
Economy, psychology, and brain science are united.
Then, in the field of brain science, much researches have been performed about the mechanism of the brain in connection with the action learning and decision-making based on remuneration for what has happened to the mechanism of the brain relevant to remuneration.
For example, when a rat turns a lever, a cerebral specific part has the experiment into which an electric stimulus flows.
This rat continues turning [ come ] a lever, without not drinking water, either but also eating food.
The electric stimulus of a certain brain part itself became the remuneration for a rat.
Moreover, a substance called dopamine is shown by the experiment of the former [ thing / which used remuneration / which is concerned for attaching a condition (study) ].
Furthermore, in research in recent years, it also understands how "quantity" and "probability" of the remuneration used as the factor as which man feels value are expressed in a brain.
The "neuroeconomics" which Associate Professor Saori Tanaka is studying is a new field which tries to make the new economic model which can explain an actual human being's economic activity better using the knowledge about the mechanism of the brain in connection with such remuneration.
Although the field the "behavioral economics" which tries to make the economic model in consideration of man's psychological element is also one of the fields of economics, the knowledge of brain science is also taken in, "economics", "psychology", and "brain science" are united, and it can be said that it is neuroeconomics that he is going to understand the action based on man's remuneration.
A joy degree decreases with time.
Associate Professor Tanaka's first subject of research clarifies man's action based on remuneration by a relation with "time."
Change comes out to the joy degree of remuneration with time, and it is called "time discounting."
Associate Professor Saori Tanaka interview time discounting leads to the degree of "self-control."
"They will be 100 doughnuts in one year."
Please explain time discounting plainly.
For example, when a doughnut is placed at hand, a joy is larger than it is said that a doughnut will be raised in one year much.
The value is felt large as the remuneration which man can get "immediately", and if the time which can be got becomes late, it will have the character in which value decreases gradually and will call this "time discounting" and "time preference" in psychology or economics.
Then, how about saying [ that 100 doughnuts will raise in one year ]?
If a discount rate (rate that value decreases) is very large, value tends to dive also in short time, tends to be in the state "I am hardly glad if it cannot immediately be given", and tends to choose one impending doughnut.
On the other hand, since value decreases gently if a discount rate is very small, it can expect choosing 100 actions in consideration of the future, i.e., a doughnut.
The action predicted from such a different discount rate can also be interpreted as "the hasty person who can judge only an immediate thing", and "those who can bear and can carry out self-control."
Thus, the idea of time discounting becomes very important at the human being's of a case so that a time lag may arise in consideration action.
Substances within a brain, such as serotonin, are studied.
Are various experiments also conducted?
It can ask for a discount rate like the example of the hamburger of the beginning by the option experiment of "the small remuneration which can be got immediately", and "the large remuneration which requires time."
Such a selection problem is called "being a between selection problem at the different time."
In the field of economics, although a discount rate is measured by the question "whether 10,000 yen is got in two days", and whether "whether the money increased how much from it to be got in nine days", this also has prior knowledge, such as interest rates, and the difficulty of being greatly affected depending on how to put a problem in order.
Then, we developed the between selection subject based on the subject of an animal experiment at the different time which it can be intuitive and can be performed easily, and have measured the discount rate.
I have you participate in an experiment from a child until now also to adults and the disease patients who have a drive impulse in condition, and it is investigating the relation between various elements called the level of substances within a brain, such as age, a social attribute and serotonin, and time discounting.
2014-11-08 07:26:21 大阪大学.
人間にとっての報酬（reward）は、お金や食べ物といった、生命の維持に必要なもの、また間接的にそれに結びつくものである。しかし、例えば100万円という報酬でも、富裕層の人が感じるうれしさと、学生が感じるうれしさは違うだろう。このように、「ある報酬にどれぐらいのうれしさを感じるか」というのは、主観的なものであることが予測される。経済学では、このようなうれしさを「効用」や「価値」と呼ぶ。近代経済学は、人々は主観的な「効用」や「価値」に基づいて行動を選択していると仮定し、人間の行動を考えている。それでは、「効用」や「価値」はどのような要素に影響されるのか？主な要素として、報酬が「たくさん」「確かに」「すぐに」もらえるほど、人は価値を大きく感じることが心理学や経済学の実証実験からわかってきた。
経済・心理・脳科学を融合
それでは報酬に関連する脳のメカニズムはどうなっているのか？脳科学の分野では、報酬に基づく行動学習や意思決定に関わる脳のメカニズムに関して、数多くの研究がおこなわれてきた。例えば、ラットがレバーを回すと、脳の特定の部位に電気刺激が流れる実験がある。このラットは水も飲まずエサも食べずに、ずっとレバーを回し続けるようになる。ある脳部位の電気刺激そのものが、ラットにとっての報酬となったのだ。またドーパミンという物質は、報酬を用いた条件付け（学習）に関わることがこれまでの実験で示されている。さらに、近年の研究では、人間が価値を感じる要因となる、報酬の「量」や「確率」が脳の中でどのように表現されているかということもわかってきた。田中沙織准教授が研究している「神経経済学」とは、このような報酬に関わる脳のメカニズムに関する知見を用いて、実際の人間の経済行動をより良く説明できるような新しい経済モデルを作ろうとする新しい分野である。経済学の分野にも、人間の心理学的要素を考慮した経済モデルを作ろうとする「行動経済学」という分野があるが、さらに脳科学の知見も取り入れて、「経済学」「心理学」「脳科学」を融合させて、人間の報酬に基づく行動を理解しようとするのが神経経済学だといえる。
喜び度合いが時間とともに減る
報酬に基づく人間の行動を、「時間」との関係で明らかにするのが田中准教授の一番の研究対象である。報酬の喜び度合いには時間とともに変化が出てきて、それを「時間割引」という。
田中沙織准教授インタビュー―時間割引が「自己統制」度につながる
「1年後に100個のドーナツ」
時間割引について、分かりやすく説明してください。
例えば、目の前にドーナツを置かれた時のうれしさは、１年後にドーナツをあげると言われるよりもずっと大きい。人間は「すぐに」もらえる報酬ほど、その価値を大きく感じ、もらえる時間が遅くなると徐々に価値が減少していくという性質を持っており、これを心理学や経済学では「時間割引」や「時間選好」と呼びます。それでは1年後にドーナツ100個あげるといわれたらどうでしょう。割引率（価値が減少する割合）がとても大きいと、価値は少しの時間でも急降下して、「すぐもらえないと、ほとんどうれしくない」という状態になり、目の前のドーナツ１個を選びがちです。一方、割引率がとても小さいと、価値は緩やかに減っていくので、将来のことも考慮した行動、つまりドーナツ100個を選ぶことが予想できます。このような異なる割引率から予測される行動を、「目先のことしか判断できないせっかちな人」と「がまんでき、自己統制できる人」と解釈することもできます。このように、報酬に時間遅れが生じるような場合の人間の行動には、時間割引という考えがとても重要になってくるのです。
セロトニンなど脳内物質を研究
いろんな実験も行われているのですね。
割引率は、冒頭のハンバーガーの例のように、「すぐにもらえる小さい報酬」と「時間がかかる大きい報酬」の選択実験により求めることができます。このような選択問題を「異時点間選択問題」と呼びます。経済学の分野では、「２日後に１万円をもらうか」「９日後にそれよりどれくらい増額したお金をもらうか」という質問によって割引率を測定しますが、これは例えば金利などの事前知識や、問題の並べ方によって大きく影響を受けるという難点もあります。そこでわれわれは、動物実験の課題をもとに、直観的で簡単に行える異時点間選択課題を開発して、割引率を測定しています。これまでに、子供から成人、また衝動性を症状に持つ疾患患者の方にも実験に参加してもらい、年齢や社会的属性、セロトニンなどの脳内物質のレベルといったさまざまな要素と時間割引の関係を調べています。
