The Delay Discounting Task measures how much participants devalue monetary rewards as a function of delay — a process known as temporal or delay discounting. On each trial, participants choose between a smaller reward available today (SS) and a larger reward available after a delay (LL). A participant who always prefers the immediate option is said to discount the future steeply (high k); one who readily waits is said to discount shallowly (low k).

This implementation uses an MCQ-inspired binary choice format — similar in structure to Kirby et al. (1999) — with 27 choice pairs spanning three reward magnitudes: small (LL ≈ £25), medium (LL ≈ £50–55), and large (LL ≈ £75–85), and delays ranging from 6 to 180 days. Each item has a pre-computed indifference k value (stored in the k_value column) derived from its specific SS, LL, and delay values.

Important for scoring: The item set in this task uses a custom k-anchor structure that does not replicate the published Kirby et al. (1999) MCQ items exactly. The published Kirby norms and geometric-mean scoring procedure are calibrated to specific item anchors and do not apply to this set. Researchers should derive individual discount rates using a switchpoint analysis (see Documentation).

Choices are self-paced (no deadline). The primary dependent measure is the proportion of LL choices overall and by magnitude category.

The task opens with 3 practice trials that show the format but whose data are excluded from analysis (column phase = "practice"). All amounts are hypothetical.