Discounting and Self-Control

MAY 19, 2009

I’m posting up an essay on “Discounting and Self-Control” (pdf). The essay, which I haven’t really touched for over a year, is still in its early stages but having lacked the time to do much on it over the last year, and going on the motto of “release early, release often”, I’m posting it up as a form of alpha version.

… then must you speak
Of one that loved not wisely, but too well;
Of one not easily jealous, but, being wrought,
Perplex’d in the extreme; of one whose hand,
Like the base Judean, threw a pearl away
Richer than all his tribe; …

Othello, The Moor of Venice


An agent’s intertemporal choices depend on a variety of factors, most prominently, their valuation of future payoffs as encapsulated in a discount function. However, it is also clear that factors such as self-control may also play an important role, and given the similarity of impact, a confouding one. We explore the literature on this issue as well as examining what occurs when those with higher time-preference (whether arising from discounting or self-control) also enjoy their consumption more.


The exercise of will, especially in the form of self-control, has long been recognized as central to human existence, experience, and morality. Over the last few decades there has been increasing interest in the issue from a scientific perspective. At the same time, it has also long been appreciated that humans (and other animals) make trade-offs between the present and the future – as well as between different points in the future, and that events taking place closer to the present are given greater weight than those which are more distant. Traditionally, at least in economics, this type of behaviour has been subsumed under the heading of discounting.

Both of these factors, self-control and discounting, affect behaviour, and choices, in relation to outcomes which do not (all) take place in the present. However they are distinct. Specifically, consider a very simple case of two outcomes A and B where B occurs after A (for example, A might be one ice cream today and B an ice cream and a doughnut tomorrow). Self-control issues arise where one prefers B over A but is unable to execute on this preference and therefore actually takes (‘chooses’) A. By contrast, in the discounting case A is actually preferred over B and therefore is chosen (freely) by the decision maker.

It would seem important to keep these two aspects of decision making clearly separated. While lack of ‘self-control’ is usually seen as disadvantageous and a reason for adopting various ‘commitment strategies’ – for example, by opting to remove various items from the choice set (having no cigarettes in the house) – the simple preference for the present over the future incorporated in the discounting model would seem to generate no such difficulties.

However, empirically it may prove rather difficult to do so. As shown by the simple example above the same observed ‘choice’ for A (one ice cream today) over B (ice cream plus doughnut tomorrow) can be the result of two very different processes. Thus if we only observe choices, and not the underlying preferences and/or the process by which the choice is arrived at, it may be impossible to distinguish the two.

It is perhaps for this reason that these distinct aspects are sometimes conflated. Consider, for example, Mischel et al 1989 which is entitled “Delay of Gratification in Children” and summarizes much of Mischel of pioneering work on this area. Mischel’s approach is clearly more oriented along the self-control aspect, and this is borne out in the types of experiments conducted (more on this below). Nevertheless they state (p.934) “The obtained concurrent associations [between treatments and delay] are extensive, indicating that such preferences reflect a meaningful dimension of individual differences, and point to some of the many determinants and correlates of decisions to delay (18).” Here the orientation towards self-control has become a general “decision to delay” and this is borne out by the associated footnote (18) which references related literature in other disciplines and is worth quoting in its entirety:

[… see full essay for more]