Preferential Choice to Exert Cognitive Effort in Children with ADHD: a Diffusion Modelling Account

Abstract

Greater sensitivity to the cost of effortful engagement has long been implicated in the development of Attention Deficit Hyperactivity Disorder (ADHD). The current study evaluated preferential choice to engage in demanding tasks, and did so in combination with computational methods to interrogate the process of choice. Children aged 8-12 with (n = 49) and without (n = 36) ADHD were administered the cognitive effort discounting paradigm (COG-ED, adapted from Westbrook et al., 2013). Diffusion modelling was subsequently applied to the choice data to allow for a better description of the process of affective decision making. All children showed evidence of effort discounting, but, contrary to theoretical expectations, there was no evidence that children with ADHD judged effortful tasks to be lower in subjective value, or that they maintained a bias towards less effortful tasks. However, children with ADHD developed a much less differentiated mental representation of demand than their non-ADHD counterparts even though familiarity with and exposure to the experience of effort was similar between groups. Thus, despite theoretical arguments to the contrary, and colloquial use of motivational constructs to explain ADHD-related behavior, our findings strongly argue against the presence of greater sensitivity to costs of effort or reduced sensitivity to rewards as an explanatory mechanism. Instead, there appears to be a more global weakness in the metacognitive monitoring of demand, which is a critical precursor for cost-benefit analyses that underlie decisions to engage cognitive control.

Keywords: ADHD; Cognitive control; Cognitive effort; Diffusion modeling; Metacognitive monitoring.

Figure 1.

Cognitive effort discounting paradigm (COG-ED). In Phase 1, children were given 1.5s on each trial to respond whether the current letter was the same as the one n back ago, which was followed by an interstimulus interval (ISI) of 3.5s. In Phase 2, children chose between performing a more difficult N-back for larger reward vs. 1-back for smaller reward. In the example trial structure depicted here, if the child chose 2-back on Trial 1, the offer for 1-back is increased by $1.25 (from $2.50 to $3.75) on Trial 2; on the contrary, if they chose 1-back on Trial 1, the offer for 1-back decreases by $1.25 on the next trial, so on and so forth.

Figure 2.

Subjective value (SV) of effort, discounted as choices include offers requiring greater effort. Lines represent (A) diagnostic group or (B) bins based on d’ on the experiential N-back across all offer load.