How Does Temporal Discounting Relate to Traditional Personality

Variables?Heidi L. Dempsey & David W. Dempsey

Jacksonville State University

Temporal Discounting• The study of temporal discounting evolved as a

behavioral method to study impulsivity• Traditionally impulsivity has been measured

using standard personality inventories such as the Barratt Impulsiveness Scale (BIS; Patton, Stanford & Barratt, 1995)

• The crux of the discounting question is, “At what point will a person take a smaller, sooner reward over a larger, later reward?”

• That is, when will people devalue long-term outcomes in favor of short-term gains?

• The point at which the person switches to preferring the smaller-sooner reward is called the indifference point.

• The less a person will take now as opposed to waiting for the delayed reward indicates higher impulsivity (e.g., choosing $950 today rather than waiting 1 month for $1000 vs. choosing $250 today rather than waiting 1 month for $1000)

• This procedure has been used extensively to show the relationship between impulsiveness and addictive behaviors such as smoking, drug abuse, gambling, and obesity (see Madden & Bickel, 2010)

• However, to date, few studies have examined how temporal discounting relates to traditional personality measures (e.g., some have found a relationship between discounting and the BIS, but others have not; deWit, Flory, Acheson, McCloskey, & Manuck, 2007)

• The purpose of the present study is to examine several personality variables that should be related to temporal discounting as a measure of impulsivity, including the BIS.

• Additionally, impulsivity will be examined in relation to students’ course grades to determine if those who are more impulsive earn lower grades.

MethodParticipants

– Introductory Psychology students participated for extra credit

• 37% male; 63% female• 59% first semester freshman• 45% African American; 44% Caucasian

– 172 completed the personality survey– 132 completed the discounting measure– 116 completed both

Temporal Discounting Measure• There were three magnitudes of reinforcers -

$100, $1,000, and a small subset received $10,000 and seven possible delays: 1 day, 1 week, 1 month, 6 months, 1 year, 5 years, and 25 years

• For each dollar amount and time delay combination, participants made six choices between the maximum future dollar amount (e.g., $100 in one month) and an adjusting immediate amount (e.g., $50 now)

• Based on their choices, the amount was either increased by half of the previous adjustment (if they chose the delayed amount) or decreased by half of the previous adjustment (if they chose the adjusting amount). The final value after six trials is recorded as the indifference point.

• The coordinates ($, delay) of each indifference point were converted to a proportion of the total amount or delay and were plotted on a graph to create an indifference curve. Then the area under the indifference curve (AUC) was calculated by the trapezoid method.

• AUC ranges from 0 (steepest possible discounting) to 1 (no discounting) for each dollar amount

Graph of Indifference Curve for $100 and $1000 for Subject 42

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1 7 31 182 365 1825 9125Delay in Days

Indifference Points as a Proportion of Total

Amount

$1,000 $100

Personality Measures• Short Form of the Need for Cognition Scale

(Cacioppo, Petty, & Kao, 1984)

• Procrastination Measure (Steel, Brothen, & Wambach, 2001)

• Internal-External Locus of Control (Rotter, 1966)

• Barrett Impulsiveness Scale - version 11 (Patton et al., 1995)

• Work Ethic and Study Ethic Questions– If you were a salaried employee making $1000 per week ($52,000

per year), how much time would you be willing to spend on activities required for your job before you decide it is not worth keeping this job?

– Number of hours a week a student is willing to study vs. socialize (e.g., study 12 hrs and socialize 8 hrs)

Procedure• Students first completed all of the personality

questionnaires online using SurveyMonkey.com• They were then asked to sign up for a time to

come to the lab and complete the computerized discounting program

• At the end of the semester, their Introductory Psychology grades were collected through Banner (JSU’s record-keeping administrative software)

Results• Correlations Between AUC, BIS, and Personality

Variables (*p < .05, **p < .01) - all impulsivity measures recoded so higher values = higher impulsivity

N=55 for $10,000, N=116 for $1000 & $100, N=168 for BIS-11

AUC for $10,000

AUC for $1,000

AUC for $100

BIS-11 Total

Need for Cognition -.22 -.06 .04 -.38**

Procrastination .24* -.08 -.02 .59**

Internal Locus of Control .20 .06 .10 -.14

Number of hours per week willing to study .05 -.02 .03 -.34**

PSY 201 Grade -.24* -.18* -.16 -.05

• Correlations Between AUC, BIS, and Personality Variables (*p < .05, **p < .01) - all impulsivity measures recoded so higher values = higher impulsivity

N=55 for $10,000, N=116 for $1000 & $100, N=168 for BIS-11

Mean hrs willing to

work

AUC for $10,000

AUC for $1,000

AUC for $100

BIS Total

Employee making $250 per week ($13,000/yr)

29.0 hrs ($8.62/hr)

-.08 -.19* .16 -.01

Employee making $500 per week ($26,000/yr)

35.7 hrs ($14.00/hr)

-.14 -.19* -.17 -.12

Employee making $1000 per week ($52,000/yr)

42.4 hrs ($23.58/hr)

-.18 -.28** -.20* -.10

Employee making $1500 per week ($78,000/yr)

45.0 hrs ($33.33/hr)

-.14 -.19* -.14 -.11

Employee making $2000 per week ($104,000/yr)

48.1 hrs ($41.58/hr)

-.15 -.19* -.16 -.07

Employee making $2500 per week ($130,000/yr)

48.7 hrs ($51.33/hr)

-.10 -.12 -.05 -.21**

• Those who received a D, F, or withdrew from PSY 201 were more impulsive according to the AUC $1,000 measure (M = .25, SD = .27) than those who received an A or B (M = .39, SD = .30), F (1, 98) = 5.03, p = .027.

• Those who received a D, F, or withdrew from PSY 201 were also more impulsive according to the AUC $10,000 measure (M = .24, SD = .23) than those who received an A or B (M = .51, SD = .29), F (1, 47) = 10.65, p = .002.

• There was no difference between the groups for the AUC $100 measure.

Discussion• The BIS-11 was a better predictor of need for

cognition, procrastination, and number of hours per week a student was willing to study vs. socialize.

• However, the AUC $10,000 and $1,000 measures were better predictors of students’ academic performance

• Additionally, AUC $1,000 was a good predictor of students’ work ethic in terms of number of hours they would be willing to work for a paycheck.

• Neither measure correlated with locus of control.

• Why the differences? – It appears that the AUC $100 is not a strong

enough measure to separate out those who are truly impulsive from those who are not.

– AUC $10,000 was closer to the BIS-11 in terms of prediction, however, the sample size was too small to have much power.

– Perhaps the BIS-11 is more closely related to other measures because they are all pencil and paper self-reports. The discounting measure is still self-report, but it does require participants to make a range of choices and may be slightly more engaging than a survey.

– However, most participants did not make consistent choices in the discounting program (most people’s indifference curves were not as uniform as #42’s curve)

• Although researchers have not found a difference between the discounting of real and hypothetical rewards (Madden et al., 2003), there has not been much research in the discounting domain with regard to personality nor academics.

• Thus, future research will examine how students discount real extra credit points to determine if their discounting of real points is related to hypothetical points and hypothetical monetary rewards.