Why Children With ADHD Prefer Smaller, Sooner Rewards

The choice, and what it is taken to mean

One point after a wait of two seconds, or two points after a wait of thirty. A child makes that choice twenty times in a row, and the number of times the single point wins is the score.

Two explanations are available for a child who keeps taking the single point. Under the first, the sooner reward simply weighs more: value falls away as delivery recedes into the future, so two points half a minute off are worth less than one point now. Psychologists call this choice impulsivity. Under the second, the waiting is itself unpleasant, and the small reward is worth having because it buys an early exit from the wait. That second account is delay aversion in its strict sense, a motive to escape the interval.

The task separates the two by removing the exit. In one condition, taking the single point moves the child straight on to the next trial, so impatience shortens the session. In the other, the small reward is followed by thirty seconds of nothing and the large one by two, so the session runs the same length however the child chooses. A child who wants only the reward sooner should behave alike in both, and the gap between the conditions is what the researchers treat as delay aversion proper.

Yannis Paloyelis, Philip Asherson and Jonna Kuntsi, at the Institute of Psychiatry, King’s College London, put 1,062 children through both conditions and reported the results in 2009 in the Journal of the American Academy of Child and Adolescent Psychiatry. The children were aged 7.9 to 10.9, half of them girls, drawn from a general population twin cohort born in England and Wales rather than from a clinic. Parents and teachers rated each child for inattention and for hyperactivity-impulsivity.

Inattention ratings predicted preference for the single point in both conditions and in both sexes, with hyperactivity-impulsivity and age accounted for. A standard deviation more inattention raised the expected share of immediate choices by 2.41 to 5.46 percentage points in boys and by 4.35 to 7.01 in girls, which amounts to between half a choice and one and a half choices out of twenty. Hyperactivity-impulsivity predicted nothing in boys at all, and in girls, in the fixed-length condition, it predicted fewer immediate choices.

On the measure built specifically to isolate the escape motive, inattention predicted the difference between conditions in boys only, adding 1.3 percent to the explained variance, and 0.9 percent once IQ was accounted for. Neither symptom dimension predicted it in girls. Setting their own figures beside those of a clinical study of 360 diagnosed children that used the identical task, the authors put the whole contribution of acquired delay aversion at between 0.9 and 2.7 percent.

What it means for you and your child

Both accounts survive this study, but they do not survive it equally. What tracked a child’s inattention ratings was the plain preference for the sooner reward, present whether or not impatience bought anything. The additional ingredient, the aversion to the waiting as such, accounted for about one percent of the differences between children, and only among boys.

Impatience on this task ran with inattention and not with hyperactivity, which reverses the usual intuition that the visibly restless child is the one who cannot wait for the better prize. Ratings of attention and laboratory measures of impulsivity are known to align poorly, and the authors are careful to say they cannot tell whether this reflects the underlying processes or the crudeness of the instruments.

None of this identifies an individual child. These are averages across a thousand children rated on questionnaires, a general population sample rather than a clinical one, and the largest effect reported moves a child by fewer than one and a half choices out of twenty. A tendency that faint across a population can still be conspicuous in one household, and the study has nothing to say about which household.

The rewards were points rather than anything a child actually wanted, a weakness the authors name themselves, and in the fixed-length condition the small reward lost its only real advantage, since taking it brought nothing sooner. A measure of the escape motive built as the difference between two such scores inherits the noise in both. What they propose instead is a physiological read on how a child responds to being made to wait, taken independently of any choice.

Delay aversion, in the version of the theory this study tested, is supposed to be learned. A child whose impulsiveness repeatedly meets a world arranged for patience is thought to acquire, over years, a genuine distaste for waiting. Testing that requires following the same children across those years, and no one has done it.

So the question of why a particular child takes the smaller reward remains open, and it will remain open until someone measures the wanting and the waiting apart from each other. Seventeen years after this study named the problem, that work has not been done, and what your child’s impatience is made of has still not been measured.