Methodological considerations in the study of delay discounting in intertemporal choice: A comparison of tasks and modes

Abstract

An experimental comparison of two commonly used delay-discounting procedures (binary choice and fill in the blank) and modes of administration (paper and pencil and computer based) was conducted. Statistically significant main effects were found for task type-steeper discounting was observed in the binary-choice taskbut not for mode of administration. As simple evidence of validity, hyperbolic curves consistently provided a better fit to the data than did exponential curves for both tasks. Further, magnitude effects were also observed across conditions. Correlational results varied largely as a function of the discounting index (either k or area under the curve) under consideration. Across the two tasks, discounting indices showed modest levels of reliability [r(AUC) .33; r(k) .75]. The findings pointed to refinements for both the methodology and criteria that are used to study delay discounting and raised questions about the commonly assumed relationship between discounting and the construct of impulsivity.

Testing the Reliability of Delay Discounting of Ten Commodities Using the Fill-in-the-Blank Method

“…Some research has focused on comparing these separate methods of measuring delay discounting (e.g., Smith & Hantula, 2008). Other research has investigated the reliability of the measures themselves.…”

“…The FITB method can also be completed quickly and theoretically identifies the exact indifference point because the participant produces an exact value. However, the FITB method may produce different indifference points than the traditional binary-choice method, possibly because it is more "cognitively demanding" (i.e., the participant has to decide how to interpret the question and then generate a value; Smith & Hantula, 2008).…”

Delay Discounting and Social Policy Issues

“…The data reflected in Figure 2 suggest that the present data resembled those typically reported. However, discounting for the monetary amount was not as steep as one might expect from the literature (e.g., Beck & Triplett, 2009;Smith & Hantula, 2008), especially given the delays used in the current study. This result may be related to the magnitude of our monetary amount (i.e., $100,000 vs. $10,000 in the Smith & Hantula, 2008, study).…”

“…Previous research has found that different methods of measuring delay discounting can result in different rates of discounting being observed (Smith & Hantula, 2008). Thus, if another method had been employed (e.g., the fillin-the-blank method; Chapman, 1996), different findings and conclusions might have resulted.…”

“…Another technique is to add an exponent to the hyperbolic equation. There is an ongoing debate as to which technique is superior (Beck & Triplett, 2009;Killeen, 2009;Smith & Hantula, 2008). Our decision to use AuC (and Equation 1) as the dependent measure was somewhat independent of this debate.…”