Time preferences are reliable across time-horizons and verbal vs. experiential tasks

Abstract

Individual differences in delay-discounting correlate with important real world outcomes, e.g. education, income, drug use, & criminality. As such, delay-discounting has been extensively studied by economists, psychologists and neuroscientists to reveal its behavioral and biological mechanisms in both human and non-human animal models. However, two major methodological differences hinder comparing results across species. Human studies present long time-horizon options verbally, whereas animal studies employ experiential cues and short delays. To bridge these divides, we developed a novel language-free experiential task inspired by animal decision-making studies. We find that subjects' time-preferences are reliable across both verbal/experiential differences and also second/day differences. When we examined whether discount factors shifted or scaled across the tasks, we found a surprisingly strong effect of temporal context. Taken together, this indicates that subjects have a stable, but context-dependent, time-preference that can be reliably assessed using different methods; thereby, providing a foundation to bridge studies of time-preferences across species. Introduction 1Intertemporal choices involve a trade-off between a larger outcome received later and a smaller outcome 2 received sooner. Many individual decisions have this temporal structure, such as whether to purchase a 3 cheaper refrigerator, but forgo the ongoing energy savings. Since research has found that intertemporal 4 preferences are predictive of a wide variety of important life outcomes, ranging from SAT scores, graduating 5 from college, and income to anti-social behaviors, e.g. gambling or drug abuse [1,13,24,28,45], they are 6 frequently studied in both humans and animals across multiple disciplines, including marketing, economics, 7 psychology, and neuroscience. 8A potential obstacle to understanding the biological basis of intertemporal decision-making is that human 9 studies differ from non-human animal studies in two important ways: long versus short time-horizons and 10 choices that are made based on verbal versus non-verbal (i.e. "experiential") stimuli. In animal studies, the 11 subjects experience the delay between their choice and the reward (sometimes cued with a ramping sound or a 12 diminishing visual stimulus) before they can proceed to the next trial [8,11,73]. Generally, there is nothing for 13 the subject to do during this waiting period. In human studies, subjects usually make a series of choices 14 (either via computer or a survey) between smaller sooner offers and larger offers delayed by months or 15 years [2, 49]. (We are aware of only a handful of studies that have used delays of minutes [48] or 16 seconds [25, 31, 40, 60, 72]). During the delay (e.g. if the payout is in 6 months) the human subjects go about 17 1/25 their lives, likely forgetting about the delayed payment, just as individuals do not actively think about their 18 retirement savings account each moment until their retirement. 19Animal studies of delay-disc...

Time preferences are reliable across time-horizons and verbal versus experiential tasks

“…Software for running the task, as well as the data and analysis code for regenerating our results are available at https://github.com/erlichlab/delay3ways/tree/v1.0 (Lukinova and Erlich, 2018; copy archived at https://github.com/elifesciences-publications/delay3ways).…”