良い習慣を身につけるのに、アメは有効か？

勉強しようとしない子に「勉強するならスマホを買ってあげる」、学校に行こうとしない子に「学校に行くなら好きなものを買ってあげる」というのは、意味がありますか？

細川院長

良い習慣を身につけさせるために、アメを使うという話ですね。

アメ（経済的インセンティブ）が習慣形成に影響するかという研究がされています。

アメは有効ですか？

細川院長

結論から言うと、短期的にはある程度有効です。

First we discuss how extrinsic incentives may come into conflict with other motivations. For example, monetary incentives from principals may change how tasks are perceived by agents, with negative effects on behavior. In other cases, incentives might have the desired effects in the short term, but they still weaken intrinsic motivations. To put it in concrete terms, an incentive for a child to learn to read might achieve that goal in the short term, but then be counterproductive as an incentive for students to enjoy reading and seek it out over their lifetimes. Next we examine the research literature on three important examples in which monetary incentives have been used in a nonemployment context to foster the desired behavior: education; increasing contributions to public goods; and helping people change their lifestyles, particularly with regard to smoking and exercise. The conclusion sums up some lessons on when extrinsic incentives are more or less likely to alter such behaviors in the desired directions.　

Gneezy, Uri, Stephan Meier, and Pedro Rey-Biel. 2011. “When and Why Incentives (Don’t) Work to Modify Behavior.” Journal of Economic Perspectives, 25 (4): 191-210.

アメは良い習慣づくりに、有効なんですね！

じゃあ、勉強するならスマホを買い与えるのもいいのかな？

……でも、短期的というのは？

細川院長

実験結果では、アメによって身についた良い習慣は、長続きしないことがわかっています。

また、アメがなくなると、習慣もやがてなくなってしまうことがわかりました。

Objectives: Uncertainty remains about whether personal financial incentives could achieve sustained changes in health-related behaviors that would reduce the fast-growing global non-communicable disease burden. This review aims to estimate whether: i. financial incentives achieve sustained changes in smoking, eating, alcohol consumption and physical activity; ii. effectiveness is modified by (a) the target behavior, (b) incentive value and attainment certainty, (c) recipients’ deprivation level. Methods: Multiple sources were searched for trials offering adults financial incentives and assessing outcomes relating to pre-specified behaviors at a minimum of six months from baseline. Analyses included random-effects meta-analyses and meta-regressions grouped by timed endpoints. Results: Of 24,265 unique identified articles, 34 were included in the analysis. Financial incentives increased behavior-change, with effects sustained until 18months from baseline (OR: 1.53, 95% CI 1.05-2.23) and three months post-incentive removal (OR: 2.11, 95% CI 1.21-3.67). High deprivation increased incentive effects (OR: 2.17; 95% CI 1.22-3.85), but only at >6-12months from baseline. Other assessed variables did not independently modify effects at any time-point. Conclusions: Personal financial incentives can change habitual health-related behaviors and help reduce health inequalities. However, their role in reducing disease burden is potentially limited given current evidence that effects dissipate beyond three months post-incentive removal.

Eleni Mantzari, Florian Vogt, Ian Shemilt, Yinghui Wei, Julian P T Higgins, Theresa M Marteau. (2015) “Personal financial incentives for changing habitual health-related behaviors: A systematic review and meta-analysis.” Preventive Medicine, 75:75-85

アメがずっと効果があるようにする方法はないんですか？

細川院長

アメの効果はこのように慣れによって弱まりますので、その効果を維持するには、報酬額を上げるしかありません。

つまり、スマホを買い与えたら、今度はそれよりも高いものを買い与えないといけない、どんどん高いものを買い与えることになると……。

細川院長

そうなりますね。

細川院長

では、この知見を臨床ではどう活かせば良いでしょうか？