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Temporal discounting
Future rewards are perceived as less valuable than immediate rewards, even when they are objectively larger.
If the value takes time to appear, deliver pieces of it along the way.
The same reward is worth less if it takes longer, and the drop is much steeper than logic suggests. Discounting of the future has been described since the 1930s, and what George AinslieDescribed the curve of temporal discounting: the value of a reward plummets as it recedes in time, and not proportionally.One reference in this work:1975Specious reward: a behavioral theory of impulsiveness and impulse controlSee in the bibliography → did in 1975 was show the shape of the curve and what it produces, preference reversal. People do not prefer the present out of preference; the value of something plummets in the first days of waiting and then falls slowly. That is why someone gives up on a six-month course on the second day, and why breaking the same journey into stages with nearby milestones changes the outcome without changing any of the content.
What the brain does with it
The biological mechanism behind the effect, and how much of it was actually measured.
The central finding is behavioural and robust: the value of a reward falls as it recedes in time, and the fall is steep in the first intervals. There is an imaging literature on intertemporal choice, and it is more disputed than popular accounts suggest. The reading of two systems in conflict, one impulsive and the other rational, is one of the interpretations, not the field’s conclusion. The design recommendation does not need it, because the discount curve is measured directly. What that literature firmly supports is where subjective value appears, in the ventromedial prefrontal cortexIt makes the global judgement, the final opinion on an entire experience, not on each moment of it. It is because of it that the person sums up a ten-screen flow in a single sentence.See it in Emotion →See in the glossary → and the ventral striatumPart of the reward circuit that tallies gain and loss. It reacts more strongly to losing than to gaining the same amount — the asymmetry behind a good part of the decision biases in this catalogue.See in the glossary →, in a survey of 206 imaging studies (BartraOne reference in this work:2013The valuation system: a coordinate-based meta-analysis of BOLD fMRI experiments examining…See in the bibliography →, McGuire and Kable, 2013). That holds for value in general, and not for the slope of each person’s curve, and the link to this bias is mine.
The body this law presumes
Who it was measured on, and what changes when the body on the other side is another.
The effect says we prefer the smaller now to the larger later, and the slope of that preference changes with how much resource the person has. ManiMeasured farmers in Tamil Nadu before and after the harvest. The same farmers did better on the tasks after being paid.One reference in this work:2013Poverty impedes cognitive functionSee in the bibliography → and colleagues measured Indian farmers before and after the harvest in 2013, and the same men did better on the cognitive tasks after being paid. What was measured there was reasoning and cognitive control, and not anyone’s discount rate. Whoever is in scarcity has less attention to spare for deciding, and that is not a character flaw, it is what worrying about money does to the attention of whoever is deciding.
How design translates it
What to do with it on a screen, without turning a finding into a rule.
How to measure this in your product
Since the value of a thing weighs less the further away it is, people avoid long tutorials and initial setups, even when the benefit at the end is clear. Well-designed systems offer micro-wins: partial rewards, quick confirmations, progress feedback. If the value takes time to appear, as in a six-month course, break the experience into pieces so that the person perceives value constantly, and make the first piece arrive on the first day. Your product’s stopwatch measures the consequence of this, how long the person holds out until the first delivery of value, and not their discount rate.
Where it breaks
Where the law does not hold, holds less, or holds in reverse.
Slicing too thin also breaks. A micro-reward on every click turns the task into a gratification machine, and the person using it loses sight of what they had come to do.
Related neuromyths
What gets said about this concept out there, and what the evidence actually shows.
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The brain has two systems, one impulsive and the other rational, and they fight over the decision.
The division into two systems is a useful descriptive model, not a map of two structures in conflict. The reading that one region “wants it now” and another “wants it later” is one of the interpretations of the imaging literature, and it is disputed. The behaviour — value falling over time — is what is measured.
Um caso
A real product where this showed up, with what happened and where to check it.
The gym that charges for not going
Two economists followed 7,752 people at three gyms in the United States, with daily attendance records, between 1997 and 2001. Those who chose the monthly contract above seventy dollars went on average 4.3 times a month and paid more than seventeen dollars per visit, when they could have paid ten with the ten-visit pass. Over the course of the membership, they missed out on saving six hundred dollars on average, and between the last visit and the cancellation an average of 2.31 paid months went by. At the moment of signing up, the person buys a future in which they go three times a week. At the moment of going, the cost of leaving the house today beats the distant benefit. The business model profits from the difference between the two moments, and the source names the two things that produce that difference, discounting of the future and overconfidence about the self-control the person will have later. Every subscription you design is betting on the same difference. It is worth knowing whether your product wins when the person uses it or when they forget to.
Experimente
A piece to check in your own body what the text has just claimed.
A mesma espera, duas respostas suas
Two questions about money, one at a time. Answer each as you really would, without stopping to do the maths.
Which do you prefer?
And now?
In both questions you wait one more month and get R$ 20 more. The only thing that changes is the distance to the first reward. When it is within arm’s reach, the value of waiting plummets, and the maths, which has not changed, loses.
Neighbouring concepts
Structures linked by a bridge of my own
- ventral striatum
- ventromedial prefrontal cortex
Sibling concepts
Fontes
Enunciado citado de Ainslie, 1975.
- AINSLIE, G. Specious reward: a behavioral theory of impulsiveness and impulse control. Psychological Bulletin, v. 82, n. 4, p. 463-496, 1975. DOI
Leitura complementar: Hyperbolic discounting Wikipedia em inglês