Individual Differences in Impulsivelike Behavior

1
Individual Differences in Impulsive-like Behavior
Sensitivity to Money as a Function of
Sensation Seeking Status LaBedz, S., Babalonis,
S., Kelly, T.H. University of Kentucky
Abstract Previous research indicates that high
sensation seekers are at increased vulnerability
to drug abuse relative to low sensation seekers.
This enhanced risk has been characterized by
earlier initiation and greater frequency of drug
use among high sensation-seeking adolescents, and
increased sensitivity to the reinforcing and
other behavioral effects of drugs in laboratory
studies, such that high sensation seekers exhibit
higher break-points on progressive ratio
schedules maintained by drug delivery. The
present study examined sensitivity to a
generalized reinforcer (i.e., money) and
impulsive-like behavior as a function of
sensation-seeking status among healthy young
adults. Twenty participants scoring in the top
and bottom quartiles of gender-adjusted
population norms on the impulsive-sensation
seeking scale of the Zuckerman-Kuhlman
Personality Questionnaire (10 high- and 10
low-impulsive sensation seekers) completed one
session in which performance on several
behavioral tasks was assessed. Participants
completed a progressive ratio task in which they
could earn up to 4.00 (in .50 increments) by
completing progressively increasing response
requirements. Other measures included
performance on the Balloon Analog Risk Task, a
hypothetical delay-discounting task, and a
delay-discounting task with a lottery outcome.
Breakpoints on the progressive ratio task did not
vary as a function of sensation-seeking status.
Likewise, performance on behavioral measures of
impulsivity did not vary between high and low
sensation seekers. These data suggest that group
differences in drug-maintained behavior between
low and high sensation seekers are not observed
when behavior is maintained by money. Moreover,
sensation-seeking status was not associated with
performance on any laboratory measure of
impulsivity (delay discounting, BART). Supported
by DA-05312, DA-024127, University of Kentucky
Department of Behavioural Science.
Results
Progressive Ratio

• Progressive Ratio Task- This task has been used
  in a variety of experimental settings to examine
  behavioral sensitivity to the reinforcing effects
  of a stimulus. The breakpoint, i.e. the last
  ratio completed, generally serves as the
  dependent measure of reinforcing efficacy. The
  selected ratio value was based on previous
  research (Stoops et al., 2007). These
  contingencies engendered variability in
  responding however, breakpoint did not vary as a
  function of sensation seeking status. Previous
  studies have shown that performance on this task
  maintained by d-amphetamine administration
  differs as a function on sensation seeking
  status.
• Money served as a reinforcer in both high and low
  sensation seekers however, there were no
  differences in breakpoints as a function of
  sensation seeking status.
• Hypothetical Delay Discounting Task- This task
  has been used to characterize behavioral
  sensitivity to reinforcer delay, such that a
  value of a reinforcer decreases as the delay to
  its delivery increases. Performance on this task
  differs as a function of current drug or alcohol
  use, gambling habits, smoking status, and age of
  first use of alcohol or illicit substance (see
  Bickel Marsch, 2001 Reynolds, 2006).
• Prototypical discounting functions were generated
  in this task however, there were no significant
  differences in indifference points as a function
  of sensation seeking status.
• Real Delay Discounting Task- Similar to the
  hypothetical task, this task generates behavior
  that differs as a function of particular
  behavioral histories (i.e., drug use, gambling,
  etc.) This task differs from the hypothetical
  task by introducing contingencies, such that one
  choice is randomly selected and rewarded (e.g.,
  15 delivered in 10 days).
• Prototypical discounting functions were generated
  in this task however, there were no significant
  differences in indifference points as a function
  of sensation seeking status.
• Balloon Analog Risk Task (BART)- This task has
  been used to examine sensitivity to reward and
  inhibitory control. Previous studies have shown
  that performance on this task differs as a
  function of drug abuse history, smoking status,
  and presence of behavioral problems (Lejuez et
  al., 2002, 2003, 2007).
• Prototypical behavior was emitted on the BART
  however behavior did not vary as a function of
  sensation-seeking status.

Earnings ()
Number of Clicks
Sensation Seeking Status

• Background
• The sensation seeking personality trait is
  described as an inclination towards intense
  emotional experiences and/or situations and the
  pursuit of risky or impulsive behavior in order
  to achieve the sensation (Zuckerman, 1994).
• Previous studies have shown that a high sensation
  seeking status may increase an individuals
  susceptibility to drug abuse (Wills et al.,
  1994).
• Previous laboratory research has shown that the
  reinforcing and behavioral effects of drugs
  (d-amphetamine, alcohol, nicotine) are enhanced
  in high sensation seekers, relative to low
  sensation seekers (Stoops et al., 2007
  unpublished data), indicating that high
  sensation-seekers may be more vulnerable to the
  reinforcing effects of drugs, and thereby might
  be at greater risk for developing repeated
  patterns of drug-seeking behavior.
• The purpose of the present study is to determine
  if the reinforcing effects of a generalized
  reinforcer (i.e. money) and performance on
  laboratory measures of impulsive-like behavior
  will differ between high and low sensation
  seekers.
• Methods
• Participants Twenty, non-smoking healthy
  adults, ages 19 to 32, gave written consent prior
  to participating in a single session lasting
  approximately 2.5 hours. Ten participants were
  classified as High Sensation Seekers, and ten
  were classified as Low Sensation Seekers, with
  each group having equal numbers of male and
  female participants. All participants provided
  drug-free urine and alcohol-free breath samples
  prior to participation. All subjects received
  task training and practice prior to the
  experimental session and were paid for their
  participation upon completion of the session.
• Sensation-Seeking Status Volunteers completed
  items from the impulsive sensation-seeking scale
  of the Zuckerman-Kuhlman Personality
  Questionnaire. Those who scored in the upper and
  lower 25 of the population, based on established
  norms, were classified as High and Low Sensation
  Seekers, respectively, and invited to
  participate.
• Assessment Tasks
• Progressive Ratio Task This task consisted of
  eight consecutive opportunities to earn money in
  increments of 0.50 by responding on a computer
  mouse. Participants could earn none, some, or
  all of the available money (4.00). To earn the
  first 0.50, participants were required to click
  the mouse 50 times. The requirement then doubled
  for each additional 0.50 (e.g., 100, 200, 400,
  800, 1600, 3200, and 6400 clicks), such that
  12,750 were required to earn all of the available
  money (4.00). However, the participant could
  choose to stop responding at any time, either by
  selecting no when asked if they wished to
  continue after earning an increment of money or
  by stopping clicking at any time (e.g., an IRT
  2 minutes ended the task). The dependent measures
  of interest during this task ware break-point
  (the last ratio completed) and concomitantly, the
  amount of money earned.
• Hypothetical Delay Discounting Task A series
  of hypothetical choices were presented, positing
  a choice between two options an immediate,
  smaller amount of money and a larger, delayed
  amount of money. The immediate amount was
  increased until preference between the two
  options reached indifference. The hypothetical
  delayed money option was fixed (1000) and was
  presented at 7 delay values (1 week, 2 weeks, 1
  mo, 6 mo, 1 yr, 5 yr and 25 yr). The dependent
  measure was indifference point for each delay
  value (I.e., the immediate amount of money that
  shifts preference from the larger, delayed
  option). Participants were instructed that each
  of their choices were hypothetical and they would
  not be paid for any of their selections.
• Real Delay Discounting Task A series of
  choices were presented, positing a choice between
  two options an immediate, smaller amount of
  money and a larger, delayed amount of money. The
  delayed money option was fixed (20) and was
  presented at 10 delay values (1 day, 3 days, 5
  days , 1 week, 10 days, 2 weeks, 3 weeks, 25
  days, 1 month, and 2 months). The immediate
  amount (20, 18, 15, 12, 10, 8, 6, 4, 2,
  and 1), was increased until preference between
  the immediate amount and the delayed amount (20)
  reached indifference. This indifference point
  served as the dependent measure. Of the 200
  choices the participants made, they were paid for
  one randomly selected choice (ex. 15 in 2
  weeks).
• Balloon Analog Task This task simulated a
  balloon being inflated in small increments
  controlled by clicking on a computer mouse (e.g.,
  Lejuez et al., 2003). On each trial a participant
  decided to inflate the balloon or move to another
  balloon. A successful inflation resulted in a
  monetary increment to a temporary bank and an
  increase in the probability of the balloon
  popping on the next inflation. If a participant
  choose to move to another balloon, the amount in
  the temporary bank was placed in a permanent
  bank if a participant choose to inflate the
  balloon and it popped, money in the temporary
  bank was lost.

Figure 1. The amount of money earned (left
panel) and total number of clicks emitted (right
panel) on the Progressive Ratio Task as a
function of sensation-seeking status. No
significant differences between groups were
detected in either measure.
Delay Discounting Tasks
Subjective value (20)
Subjective Value (1000)
Time (days)
Figure 2. Mean discounting curves generated
under real (left panel) and hypothetical (right
panel) conditions when indifference points are
fit to the hyperbolic discounting function A
V/(1kD). Both graphs display prototypical
discounting functions, with the
subjective value of money decreasing as a
function of delay to its delivery. No
differences in discounting functions between
groups were detected in either task.
Balloon Analog Risk Task
Conclusions

• There were no differences detected in behavioral
  sensitivity to a generalized reinforcer or delay
  to a reinforcer as a function of sensation
  seeking status.
• Behavioral effects were not significantly
  different with respect to other factors such as
  gender, age, and education.
• The lack of significant difference on performance
  task measures between the personality groups may
  be attributed to the heterogeneous nature of
  impulsivity and the reliability of quantitative
  measures of personality as a predictor of
  behavior.
• Previous studies have shown that the reinforcing
  effects of drugs differ between high and low
  sensation seekers. However, no differences were
  observed when a generalized reinforcer was
  available. These results suggest that
  differential sensitivity to reinforcers as a
  function of sensation seeking status may be
  specific to certain commodities (i.e., drugs).

Responses per Balloon
Number of Pops
Earnings ()
Sensation-Seeking Status
Figure 3. Mean number of responses per balloon
on balloons that did not pop (left panel) mean
number of popped balloons (middle panel) and mean
earnings as a function of sensation-seeking
status. Each bar represents the mean of three
task presentations with error
bars representing - one standard error of the
mean. No practice effects were detected across
the three task presentations for either group and
no significant differences between groups were
detected on any measure.