Tradeoffs between sequences: weighing accumulated outcomes against outcome-adjusted delays.

We extend the recently proposed tradeoff model of intertemporal choice (Scholten & Read, 2010) from choices between pairs of single outcomes to pairwise choices involving two-outcome sequences. The core of our proposal is that choices between sequences are made by weighing accumulated outcomes against outcome-adjusted delays. Thus extended, the tradeoff model offers a unified account of recently discovered anomalies in pairwise choices involving two-outcome sequences, including (a) the hidden-zero effect, in which explicit reference to the zero outcomes of the options increases patience, (b) the front-end amount effect, in which the addition of a front-end amount to both options decreases patience, and (c) the mere token effect, in which the addition of an early outcome to both options increases patience. Not only does the extended tradeoff model accommodate these anomalies, it also correctly predicts (d) violations of independence, (e) a reversal of the front-end amount effect, (f) the effect of relocating the front-end amount to the back end of both options, and (g) a dependence of the "mere" token effect on the magnitude of the token. In quantitative analyses, the extended tradeoff model offers an accurate account of the data.