© 1987 Elsevier Science Publishers B.V. (Biomedical Division)
A lcohol, drugs and traffic safety — T86
P .C . Noordzij and R. Roszbach, editors.
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THE EFFECT OF BAC AT .08% BY VOLUME UPON SKILL AND RISK-TAKING
TENDENCY IN A RESPONSE-TIMING TASK
REMI JOLY and GERALD J.S. WILDE
Department of Psychology, Queen's University, Kingston, Ontario K7L 3N6, Canada
BACKGROUND AND RATIONALE
In contrast to the well-known association between blood-alcohol level
and traffic
accidents, the precise mediating mechanism responsible for this association has not
been clearly identified (Browning and Wilde, 1975; Wilde, 1985). Among the various
possible mechanisms (Mitchell, 1985), the one explored in the present experiment is
that alcohol consum ption makes people less averse to risk. Unlike earlier
investigations of subjects' ability to react as fast as possible, the present laboratory
experiment examines the effect of alcohol ingestion on their skill in responding at
the prope r moment. This is arguably more relevant, as fluency and safety in driver
behaviour may generally depend more on adequate timing of one's actions than on
response speed per se.
M oreover, an attem pt is made to draw a clear conceptual and operational
distinction between timing skill on one hand, and bias towards either hazardous
(risk-loving) or cautious
(risk-averse) responding on the other.
Subjects' timing
skill and bias regarding risk are measured by analysing various aspects of their
performance on a somewhat modified and debugged version of an earlier computer
game
specially developed for this purpose (Wilde, Claxton-Oldfield and Platenius,
1985). Like Cownie's (1970), this game (in contrast to the experiment by Cohen et al.,
1958) confronts the player with real - be it not physical but monetary - risk and
presents him (unlike other experiments; Mittenecker, 1962; Naatanen and Summala,
1975; Veling, 1984) with the dual uncertainty of risky decisions: uncertainty of
performance due to imperfections in skill and uncertainty of consequence. These are
both proposed to be involved in driver behaviour.
S ubjects' perform ance on this game may be analysed in order
to obtain
quantitative measures of their skill as well as strategy, and in this respect it may be
an improvement upon Cownie's. Due to imperfections in any subject's timing ability,
they experience a degree of uncertainty in their performance and cannot help but
make errors. If they respond too fast on a given trial, they may or may not incur a
penalty (an 'accident' so to speak) with a predeterm ined probability, and this
constitutes uncertainty of consequence. If they respond rather slowly, they will not
accumulate as many points astheywould, had they responded a little faster, but not too
fast. So, the subjects may either err on the safe side, or on the risky side. The game is
arranged such that if they err on the risky side, they will collect many points but
also lose many. If they err on the safe side, they will not lose many points, but their
gains w ill be small. For each subject the o p tim a l
amount of risk-taking can be
calculated from the responses given and compared with the actual degree of
risk-taking, and thus individuals may be classified as risk-loving, as risk-neutral or
as risk-averse. Subjects in the first group are too daring,
those in the second
optim ize the amount of risk so that their net points earned reach the maximum
attainable within the boundaries of their skill, and the subjects in the third category
are too cautious.
It was hypothesized that BAC at 80 mg per 100 ml, would (1) reduce subjects'
tim ing skill, (2) make them more risk-loving, (3) less sensitive to the actual
occurrence of penalties, and (4) relatively more risk-loving when the likelihood of
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penalty is low as compared to when the likelihood of penalty is high.
SUBJECTS, APPARATUS AND PROCEDURE
Subjects were 36 male students at Queen's University (mean age 21.2 years, range
19-31) who all reported to be regular users of alcohol. They paid a $5 participation
fee in return for the prospect of receiving a generous drink and of winning a total of
$240 in prizes. Each played the video game individually in two sessions, separated by
one week, exact to the hour. Thus, they were made thoroughly familiar with the game
before the competitive part and the alcohol were introduced. In the first session no
subject received alcohol, in the second 18 randomly selected subjects did and did so
knowingly. There were separate prizes for the sober and the alcohol group. In each,
the best player received $60, the second $40 and the third $20.
In the alcohol condition subjects drank .70 g ethanol (in vodka mixed with orange
juice) per kg of body weight, to induce a peak BAC between 80 and 100 mg per 100 ml
(Dubowski, 1985). This was consumed in 5 minutes' time and the subjects started the
game (which took about 40 minutes) exactly 35 minutes later. All subjects had been
asked to refrain from eating 4 hours prior to the second session.
The video game challenges the subject to cancel (by using any key on a numeric key
pad) a 3x3 cm bright square displayed (at unpredictable onset times varying between
700 and 1500 ms after the preceding trial in the centre of a monitor connected to and
mounted on top of an Apple lie micro-computer) as close as possible to 1500 ms after
its appearance. A response at 1500 ms is rewarded with the maximum number of
points (i.e., 5). Slower responses earn proportionally fewer points; at 3000 ms and
beyond the p a y-off is zero. However, responses fa ste r than 1500 ms (i.e.,
undershoots) are followed by a probabilistic penalty of 5 points, which occurs either
in 20 or 80% of the undershoots. Non-penalized responses at <1499 ms yield zero
points for the trial in question. So, the expected value of undershoots is either
-.2x5=-1 or -.8x5=-4. The pay-offs in terms of sure gains and uncertain losses for
the latter case are graphed in Fig.1.
After being fu lly in fo rm e d
of all relevant conditions and contingencies, every
subject firs t perform ed 40 skill acquisition/assessm ent tria ls (w ithout accruing
points to the prizes) and then 100 experimental trials at each probability level of
penalty, the order of the latter being counterbalanced between subjects. Immediately
following a response on each skill assessm ent trial, the monitor displayed feedback
in terms of the serial number of the preceding trial, the actual response time in ms,
the average deviation (called "average stray") from 1500 ms and the number of
undershoots and overshoots relative to 1500 ms across all preceding trials. Each
e x p e rim e n ta l tria l
was followed by a display of inform ation containing the trial
number, the actual response time in ms, the number of points (rounded to one digit
beyond the decimal point) gained or lost on the trial and the number of points
accumulated across all preceding trials.
175
-1 +
-2
--
-3 --4 •—
♦
Fig. 1. Probabilistic losses (in the .8 likelihood of penalty condition)
and sure gains as a predetermined function of response time
Thus, the independent variables (all referring to the second session for
each
subject) were (1) alcohol ingestion, (2) the probability of penalty being set at .2 or .8,
and (3) the order of the experimental trials in terms of the latter. Dependent
variables - as far as they can be considered here - were the following:
(a)_timing skill (or rather lack of it), defined as the average absolute deviation
from 1500 ms in the 40 skill assessment/practice trials in the second session,
(b)_net points earned across both probability of penalty conditions,
(c)_risk-loving or risk-averse responding bias, calculated as the extent and
direction of the difference between the the subject's actual mean response time on
the one hand, and the mean response time at which (given the dispersion of his
responses) his net number of points earned would have maximized on the other,
(d)_sensitivity to occurrences of penalties, defined as the mean response time on
trials immediately following a p e n a liz e d undershoot minus the mean response time
on trials immediately following the occurrence of a non -p e n a lize d undershoot, and
(e)_difference in bias with respect to risk as defined under (c) displayed between
the trials with the high and the low probability of penalty.
RESULTS AND DISCUSSION
The data, subjected to analyses of variance (for lack of space not detailed here),
reveal no differences in timing skill as assessed by the 40 practice trials in the first
session between the subjects randomly assigned to the alcohol group and those
assigned to the sober group (two-tailed p =.8), thus indicating adequate matching.
In agreem ent with Hypothesis 1, the subjects under the influence of alcohol
showed significantly less timing skill in their second session than their sober
counterparts (one-tailed p •<.02). They also showed lower net earnings (dependent
variable b; one-tailed p <.04). No empirical support could be found for Hypotheses 3
and 4 by inspection of the between-groups differences in the dependent variables (d)
and (e). However, contrary to expectations (Hypothesis 2), the alcohol group behaved
176
in a less risk-loving m anner than the sober controls (as assessed by dependent
variab le (c); if one-tailed, p <.05). This finding, w hile obviously in need of
cross-validation, should be viewed in the context of various other features of this
experim ent, including the alcohol dosage and the selective factors that may have
played a part in the choice of subjects. It should be noted that about 90% of the
subjects in this experim ent, when sober, were risk-loving as defined above. The
possibility that alcohol consumption makes individuals, who are normally risk-averse
(and thus arguably less likely to participate in an experiment such as the present
one), more risk-loving may also be worthy of further study.
Of further interest is that the net points earned by the subjects depended primarily
on their risk-taking tendency and were only weakly related to their level of skill,
w hile there was no sig n ifica n t association between the la tte r two variables
(two-tailed p values varying between .18 and .44). As expected for reasons explained
elsew here (W ilde et al., 1985), subjects' inclination or disinclination towards risk
(dependent variable c) was not influenced by whether the probability of penalty was
set at .2 or .8. Finally, the real-life significance of findings in laboratory experiments
like the present one remains to be assessed.
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