Blood alcohol level (BAL) determinations
vere made on all subjects before they were given
he alcohol or placebo. In addition, the experi-
rental subiects had blood samnles drawn for
3AL determinations at one and two hours after
aey were given the alcohol. Testing on the
roblem-solving task oceurred about halfway
etween the first and second hour BAL deter-
iination. Results of these BAL determinations
re summarized in Table 1. The mean BAL
aross subjects was 94.5 mg% which approxi-
1ated the target figure of 100 mg%.

TasLeE 1.—Blood Alcohol Levels in mg %.

1 hour 2 hours Mean of
after after Land 2
ingestion _ ingestion hours
roupA M 99 95 97
Ss 25 22 19
roupB  M 96 87 92
s 22 18 18

The subjects were trained and tested indi-
dually with all training and testing sessions
llowing essentially the same procedure. Dur-
g training, the task was explained to the sub-
ot and the experimenter demonstrated the
‘ution of one complete problem (first and
xond solution). Then the experimenter “talked
2 subject through” one other problem. Addi-
nal instruction was given if necessary until
2 subject solved one complete problem by fol-
ving the correct procedure with essentially no
sistance from the experimenter. The subject
s then allowed to work five practice problems
dle the experimenter observed through a half-
vered mirror from the adjoining room. When
sessary, the subject was reminded, via inter-
n, to follow the proper procedure.

Che testing sessions consisted of 18 problems
vo solutions each). The duration of each
ting session was dependent on the length of
te it took each subject to complete the 18 prob-
1s. Prior to each testing session, the subject
tked one complete practice problem and the
verimenter corrected any errors in procedure.
“he subject was then reminded to work as
idly as possible while trying to avoid making
aecessary errors. The experimenter then en-

tered the adjoining room and momentarily
turned the task off while activating the scoring
cirenitry. The subject was alerted via the inter-
com system, and the task device was turned on
to start the testing session. Voice contact with
the subjects during the testing period was kept
to a minimum,

The testing schedule for the three groups is
summarized below.

1. Pre-Aleohol Day. Only the alcohol-second
group was tested on a pre-aleohol day, and these
subjects were not exposed to vestibular stimula-
tion on this day. The subjects were trained on
the task and, immediately following training,
were tested on 18 problems, with each problem
being solved twice.

2. Alcohol Day. First, subjects in all groups
had pre-drinking BAL blood samples drawn,
immediately after which Ss in the control group
and the alcohol-first group were trained on the
problem solving task. Then they were given
their drink, either alcohol or placebo, One hour
after ingestion, blood samples were drawn on
Ss who had received alcohol and all subjects then
experienced a period of rotational vestibular
stimulation. Following this, (about 114 hours
after receiving their drink) all subjects were
tested on the problem solving task; another blood
sample was drawn after code-lock testing was
completed, i.e., at two hours after they received
alcohol.

38. Post-Alcohol Day. Following a period of
rotational vestibular stimulation, control and
alcohol-first subjects were again tested on code-
lock.

All subjects were tested on the same set of 18
problems on the alcohol day; a second set of 18
problems was used on the post-alecohol sessions;
the alcohol-second group was given a third set
for their pre-alcohol testing.

TL

The data from the experimental groups were
analyzed using a Lindquist Type II design in
which day of receipt of alcohol was the Latin
square factor. The sources of variance in each
of the 11 analyses were: day of testing (first vs.
second day); alcohol (vs. no alcohol); group
(order of testing with respect to the alcohol/
no alcohol conditions) ; and subjects. The re-
sults of these analyses are summarized in Table

Results.



ory and/or memory-to-response encoding are
also implicated for this measure.

Efficient performance during the second solu-
tion is almost entirely dependent on short-term
memory and the memory-to-response encoding
process. However, the occurrence of errors dur-
ing the second solution could also be the result
of motor involvement. Although this study does
not afford a means for clearly distinguishing
between these two possibilities, the separation
between buttons (2.4 cm) would seem to make
“aiming” a relatively small factor. Thus, we
are inclined to conclude that the obtained effects
are in the informational rather than the motoric
domains.

Several factors that are present in the aviation
environment were not included in this experi-
ment. Three of these are of direct relevance to
the interpretation of the findings in relation to
flying skills. First, the problem-solving task can
be thought of as involving a homogeneous set of
behaviors. In contrast, the pilot is required to
exercise a variety of behaviors, and, of even
greater importance, he is required to time share
their performance. Thus, as suggested by our
previous study (Chiles and Jennings, 1970), if
time sharing were added to the situation, the
detrimental effects of alcohol would be expected
to be enhanced. Second, the nature of the prob-
Jem solving task is such that the subject can
adjust his speed of response as a way of avoiding
errors if he interprets the potential effects of
alcohol to be likely to lead to errors; this is in
fact what the subjects in this study did. In the
operation of an aircraft, the pilot has rather
limited freedom in making such adjustments and,
in emergencies, may have no room for adjustment
of his “speed of response.” And, third, the pilot
is subjected to a variety of potentially disturbing
motions of the aircraft which, as reported by
Collins, Gilson, Schroeder, and Guedry (1971),
tend to enhance the effects of alcohol on per-
formance. Factors such as these are undoubtedly
the reason that Billings, Wick, Gerke, and Chase
(1971) found significant decrements in pilot per-
formance at blood alcohol levels that were sub-
stantially lower than those used in the present
study.

V. Summary and Conclusions.

Three groups of subjects were tested on two
separate days on a simple problem-solving task

which required them to discover the correct se-
quence in which to push five buttons in order to
turn on a green light; the correct sequence was
then re-entered after a 10-second delay. One
group of subjects (N=10) received alcohol on
the first day and nothing the second; a second
group (N=10) received nothing the first day
and alcohol the second; the third group (N=11)
received a placebo the first day and nothing the
second. The group that received alcohol the
first day and the placebo group were also sub-
jected to vestibular stimulation on both days;
the alcohol-second group received vestibular
stimulation only on the second day of testing.
The average blood alcohol level for the experi-
mental groups was about 94.5 mg%.

Alcohol as a main effect was significant for
five of the 11 measures analyzed; three of the
significant effects found were for second-solution
performance, one was for first-solution perform-
ance, and one was for the solution time per
problem which included both solutions. One of
the measures that was affected by alcohol was
errors on the second solution; the other fow
were time measures. Analysis of the simpk
effects showed that alcohol has a greater effec
during the time when the task is still being
mastered than after a day’s practice (18 prob
Jems) has been given. However, there is sug
gestive evidence from the error measure, second
solution performance, that the performance o
practiced subjects may also be adversely affectec
by alcohol. There was also suggestive evidenc
of a residual effect of the vestibular stimulation
on the problem-solving performance of the con
trol group.

We conclude that alcohol does have an effec
on problem solving of the sort used in the presen
study and that the effect is greater on subject
when they are less practiced than when they ar
more experienced on the task. We also tenta
tively conclude that there may be a residua
effect. of vestibular stimulation per se on per
formance even though some time has elapse
since the rotational experience. Further researc.
is required to clarify this point, but, if the find
ing does prove reliable on replication, then th
implications with respect to recovery times i
the case of pilots could be very important.


solution. Time per problem (first and second
solutions combined) also showed a significant
effect.

‘The individual cell means for the five measures
for which a significant alcohol effect was found
are shown in Tables 3 through 7 along with the
day-1 and day-2 means for the control group.
Individual “t” tests were applied to the differ-
ences between days for each of the alcohol groups
treated separately. The performance of the
alcohol-first. group was significantly better on
day 2 than on day 1 (p<.05) for five of the
measures (Tables 3, 4, 5, and 7); only errors on
she second solution did not differ significantly
veross days (Table 6). The only significant
lifference found across days for the alcohol-
second group was in the case of the time per
oroblem measure (both solutions combined). It
san be seen in Table 7 that, for this measure,
verformance on day 2 (the alcohol day) was
‘ignificantly superior to that on day 1 (p<.05) ;
1ote also that the direction of the effect for this
est is opposite that found with the overall “F”
est for the effect of alcohol (Table 2). For two
of the measures, the performance of the alcohol-
econd group was faster on their alcohol day
day 2) than on day 1, but the differences were
ot significant; the measures were time per cor-
ect response (first solution) shown in Table 3
nd time per response (second solution) shown
1 Table 4. For time per solution (second solu-
on), the mean performance on the two days
vas the same for the alcohol-second group (Table
). Only the error measure on the second solu-
on (Table 6) was in the direction of better
erformance on day 1 than on day 2 for the
\cohol-second group, but that difference was not
gnificant.

‘apie 3.—Cell Means for Time Per Correct Response—
First Solution.

Tani 4.—Cell Means for Time Per Response—Second

Solution.
Day
a
1 2
Alcohol First... 1,03* 79
Alcohol Second... .81 75
Control. ..---2. .91 7)

*The value underlined is for the session on which the
group received alcohol.

Tasux 5.—Cell Means for Time Per Solution—Second

Solution.
Day
1 2
Alcohol First _ - 6. 6* 4,2
Aleohol Second_ - 4.4 4.4
Control. _.-.-.--- 5.4 4.0

*The value underlined is for the session on which the
group received alcohol.

Tasty 6.—Cell Means for Errors Per Solution—Second

Solution.
Day
1 2
Alcohol First__.___- . 66* 16
Alcohol Second. 16 +35
Control. ...--..--- 144 «16

*The value underlined is for the session on which the
group received alcohol.

Taste 7.—Cell Means for Time Per Problem—First
Plus Second Solution.

teohol First _ 1,35*
cohol Second. 1.7
ontrol_ 1.29

Day
1 2
Alcohol First... 32.0% 20.8
Alcohol Second_ - 26.8 22.8
Control . 29.4 20.0

*The value underlined is for the session on which the
oup received alcohol.

*The value underlined is for the session on which the
group received alcohol.



2, For each measure, the means for the two
levels of each of the variables and the “F” value
for the test of the effect are shown.

The order of testing with respect to the day
of administration of alcohol is reflected in the
difference between groups in this design. In no
case was that difference significant.

The practice effect was significant for all
but three of the 11 measures. With the excep-
tion of those three measures, performance on day
2 was significantly better than on day 1. Two
of the measures that did not show a significant
difference between day 1 and day 2 were error
measures, namely, errors per solution for first
solution and errors per solution for second solu-
tion. The third measure for which no difference
was found was the time per incorrect response
for the second solution. However, this latter
measure is based on a relatively small number
of responses and a reduced number of subjects.
Since seven of the 20 subjects made no incorrect
responses during the second solutions on one or
both testing sessions, the four subjects in the
alcohol-first group and the three subjects in the

aleohol-second group who made no errors wer
dropped from the analysis, along with one sub
ject selected at random from the alcohol-secon:
group. For the remaining six subjects per grouy
the time per incorrect response for the secon
solution was based on an average of only si
responses per session. For all of the other tim
measures, the difference between day 1 and da
2 was significant with better (ie. faster) per
formance occurring on day 2. Specifically, tir
per response, time per correct response, and tir
per solution for both first- and second-solutic
phases of performance treated separately differe
significantly for the two days of the study; tin
per incorrect response differed significantly fc
the first solution only; and time per proble
differed significantly for the two soiutions con
bined.

The main effect of alcohol was significant f:
only one measure taken during the first-solutic
phase of testing; that measure was the time-pe
correct response. The alcohol effect was signi
cant for three second-solution measures—tir
per response, time per solution, and errors p

‘Tapie 2.—Means and F Ratios for Analysis of Variance.

Time Per ‘Time Per
Time Per Correct. ~—Incorrect. += Time Per Errors Per Time Per
Response Response Response Solution Solution —- Problem
First Solution
Mean Day 1 1,35 1.26 1,46 23.3 +88 14.7
Mean Day 2. 1.14 Lu 1.20 18.1 -50 10.9
F (df=1/18) - 15,53" 17,234 3, 83 16, 2244 1.19 23.78"
Mean with Alcohol_. - 1.27 1.28 1.36 21.6 £97 13.7
Mean without Alcohol. - 1,22 14 1,30 19.7 241 11.9
F (df=1/18)--.---22--2---2----- 1.07 5.09% 1.09 20.7 2,51 5.09%
Mean Group A. - 1.27 1,28 1.36 20.7 174 13.2
Mean Group B. - 1,21 1.04 1.30 20.6 64 12,4
F (df==1/18) -- x x x x x x
Second Solution
Mean Day 1 - -92 90 1.18 5.5 46
Mean Day 2 - 7 277 88 4.3 £27
¥F (di=1/18) 17.53%" 15,52 3.84 5, 95** 1.29
Mean with Alcohol... -- -89 86 1.08 5.5 55
Mean without Alcohol - -80 .80 -99 4.3 +18
F (df=1/18) 5.91* 3.40 x 6.30%" 5. 43**
S 1
Mean Group A. - 91 -89 1.06 5.4 AT
Mean Group B. - 78 77 1.00 44 +26
F (df=1/18) -.- - 1.07 1.99 x 1.78 2.83
*p<.05 **p<.0l HD <.001 X F<1.0

4


twu groups may have been in part a result of an
alcohol effect, in part a residual of this having
been their first exposure to vestibular stimula-
tion, and in part an interaction of the two vari-
ables. The significant differences on this measure
between the alcohol-first and the alcohol-second
groups on day 1 is even less clear. The control
group was also poorer than the alcohol-second
group but better than the alcohol-first group,
though not significantly so in either case. Thus,
again, the apparent effect cannot be unambigu-
ously attributed to any one of the experimental
variables,

The effect of the order of testing with respect
so the administration of alcohol could not be
neasured with any great degree of sensitivity
in this study. Since this was a between-subjects
somparison, 10 subjects per group does not af-
ford much statistical power for the direct test of
che order effect. However, there were indications
n the individual tests of the simple effects of
Ucohol and the. simple effects of practice that
uggest that there was in fact an interaction
yetween the two variables. For one measure,
‘ime per problem (first and second solutions
combined), the alcohol-second group performed
tignificantly faster on day 2 (with alcohol) than
m day 1 despite the fact that the overall effect
vf alcohol was significant and in the other direc-
jon for this measure. This suggests the possi-
nility that subjects who are motivated to do well
m a task will adjust their speed to take account
of what they perceive to be possible effects of
Jcohol on their performance. And it also sug-
rests that the amount of adjustment (reduction
n speed) will be greater on a relatively new
ask (aleohol-first group) than on a task with
vhich the subject has become somewhat familiar
aleohol-second group). It may well be that
his is an important aspect of the increased er-
ors for the alcohol-second group on day 2. They
neorrectly perceived the potential for disruption
aused by the alcohol and, as a result, went too
ast to avoid making second-solution errors.
ne is tempted to conclude that their judgment
vas impaired by the alcohol, but that conclusion
vould be an unwarranted extrapolation in view
f the confounding noted previously.

There are three primary mechanisms in the
erformance of the code-lock task that might be
fected by the blood alcohol levels found with
hese subjects, namely, perceptual-motor skill,

short-term memory, and “memory-response” en-
coding. Although the first solution phase of the
code-lock task is ostensibly a problem-solving
situation, performance generally becomes a
rather simple, repetitive process that is fairly
automatic when the subject has a small amount
of practice. The limiting factors on performance
during this phase are motor skill in pressing
buttons, speed of reaction to the error feedback
light, short-term memory, and memory-response
encoding. Short-term memory is clearly im-
portant in re-entering partial solutions following
an error. It is also important in executing the
search sequence, since any button that is a mem-
ber of the already-discovered partial solution
must be eliminated from the search sequence.
Short-term memory is perhaps even more im-
portant in the second solution phase; the subject
must remember the correct sequence discovered
in the first solution phase and, after a 10-second
delay, re-enter that sequence. Speed of response
to the feedback lights was generally not im-
portant since the subjects tended to enter the
second solution without reference to the lights.
Since the lights were separated from the push-
buttons by a vertical distance of about 10 cm
(4 inches), it was possible to determine by ob-
servation where many of the subjects were focus-
ing their attention. They seemed not to be
looking at the feedback lights during the second-
solution phase. This can also be inferred from
the fact that it was not uncommon for a subject
to enter a complete 5-button sequence even
though intermediate responses were incorrect.
The pattern of significant effects on the code-
lock measures suggests that the most likely
mechanism for an effect of alcohol was interfer-
ence with short-term memory and/or the mem-
ory-to-response encoding mechanism. During
the first solution phase, only time per correct
response and solution time were affected by al-
cohol. The number of correct responses during
this phase of the task is constituted primarily
of responses made in re-entering partial solu-
tions, a process that depends heavily on short-
term memory. Solution time for a given
problem is a function of both speed of response
and the number of surplus errors, but, because
relatively few surplus errors were made (an av-
erage of Jess than one error per problem), speed
of response in re-entering partial solutions is the
dominant component. Hence, short-term mem-



TECHNICAL REPORT STANDARD TITLE PAGE

T. Report No. 2. Goverament Accession No. 3. Recipient's Cotolog No.
FAA-AM-72-11
T Title ond Subtitle 5. Report Date
March 1972
EFFECTS OF ALCOHOL ON A PROBLEM SOLVING TASK & Performing Organization Code
7 Rather's) @. Performing Organization Report No.

W. Dean Chiles, Ph.D.
Alan E. Jennings, B.A.

9. Performing Organization Nome ond Address 10. Work Unit No
FAA Civil Aeromedical Institute
P. O. Box 25082 TT, Contract or Grant No.

Oklahoma City, Oklahoma 73125

13. Type of Report and Period Covered

2. Sponsoring Agency Name ond Address

Office of Aviation Medicine OAM Report
Federal Aviation Administration
800 Independence Avenue, S. W. 14. Sponsoring Agency Code

Washington, D. C. 20591

5. Supplementary Notes

This research was conducted under Task No. AM-A~71-PSY-13,

8 Abstract

Twenty subjects were tested on two separate days on a simple problem-solving
task, Half of the subjects received alcohol on the first day of testing and
half on the second day of testing. A control group of 11 subjects was also
tested on two days and they were given a placebo on the first day of testing.
All 31 subjects were also serving in a vestibular stimulation experiment.

A significant effect was found for alcohol with five of the eleven measures
analyzed; four of the measures were time measures and one was an error
measure, Analysis of the simple effects indicated that alcohol had a greater
effect on the group that had alcohol on the first session than on the group
that had alcohol second. There was also suggestive evidence of a residual
effect of the vestibular stimulation on the problem-solving performance of
the control group. In general, the findings provide supportive evidence of
the potential deleterious effects of alcohol on a skill of importance to
aviation operations.

7 Key Words 18, Distribution Statement
Availability is unlimited. Document may
Alcohol be released to the National Technical
Problem Solving Information Service, Springfield, Virginia
Vestibular Stimulation 22151, for sale to the public.
[Security Classif. (of this report) 20. Security Classil, (of this page) TI. No. of Pages | 22. Price
Unclassified Unclassified 9 $3.00

sm DOT F 1700.7 (2-69)





a

y

. Carpenter,

REFERENCES

. Billings, Charles E., Robert L. Wick, Jr, Ralph J.

Gerke, and Robert C. Chase: The Effects of Alcohol
on Pilot Performance During Instrument Flight.
Final Report, FAA Contract No. FA68AC-6089-2,
Project No. RF-2626, Office of Aviation Medicine,
Washington, D.C., 1971.

Jolin A., and Bruce M. Ross: Effect of
Alcohol on Short Term Memory, QUARTERLY
JOURNAL OF STUDIES ON ALCOHOL, 26:561-
579, 1965.

Chiles, W. Dean, and Alan E. Jennings: Effects of
Alcohol on Complex Performance, HUMAN FAC-
TORS, 12:605~-612, 1970.

Chiles, W. Dean, and Roger C, Smith: A Non-
Verbal Technique for the Assessment of General
Intellectual Ability in Selection of Aviation Per-

a

sonnel. FAA Office of Aviation Medicine Report
No. FAA-AM-71-28, 1971.

Collins, William E., Richard D. Gilson, David J.
Schroeder, and Frederick E. Guedry, Jr.: Alcohol
and Disorientation-Related Responses. III. Effects
of Alcohol Ingestion on Tracking Performance
During Angular Acceleration. FAA Office of Avia-
tion Medicine Report No, FAA-AM~-71-20, 1971.

. Lindquist, E. F.: Design and Analysis of Eaperi-

ments in Psychology and Education,
Mifflin Company, Boston, 1953.

Tarter, Ralph E., Ben M. Jones, C. Dene Simpson,
and Arthur Vega: Effects of Task Complexity and
Practice on Performance During Acute Alcohol
Intoxication, PERCEPTUAL AND MOTOR SKILLS,
53 :307-318, 1971.

Houghton



In addition to the above “across-days tests,”
individual “t” tests were applied to the differ-
ences between groups for each day treated sepa-
rately. For the day-1 comparisons, significant
differences between groups were found only in
the case of the time per response measure (second
solution). For this measure, shown in Table 4,
the performance of the aleohol-first group was
significantly poorer than that of both the aleohol-
second (p<.05) and the control groups (p<.05).
And the performance of the contro] group was
significantly poorer than that of the alcohol-
second group (p<.05). (Note that the control
group underwent vestibular stimulation imme-
diately prior to testing whereas the alcohol-
second group did not). For the day-2 compari-
sons, no significant differences were found.
However, for the errors per solution (second
solution), the differences between the alcohol-
second group and the other two groups ap-
proached significance (.10>p>.05) with the per-
formance of the alcohol-second group being
inferior to that of the other two groups (Table
6). Since the control group and the alcohol-first
group did not differ on this meansure, these two
groups were combined and an “F” test was
applied to the difference between the combined
groups and the alcohol-second group. This dif-
ference was significant at the .05 level of
confidence.

IV. Discussion.

The significant practice effect for time but not
error measures suggests that subjects followed a
strategy of trying to minimize errors by holding
their speed of performance to a value that would
permit achievement of that goal. The subjects
apparently followed the search procedure rather
carefully on the first solution as seen by the very

_small number of surplus errors when a correction
is made for the expected errors for a given prob-
lem. And the errors were even less frequent for
the second solution, The error-minimization
strategy is also revealed by the fact that between-
subject variance accounted for about 40% of the
total variance for the error measures whereas it
accounted for about 70% of the variance on the
time measures. This finding that individual
differences on this task are measured primarily
by time measures is consistent with the findings
of an earlier study by Chiles and\Smith (1971)
in which significant correlations with the Otis

test of mental abilities were found for the time
measures but not for the error measures.

Although « significant main effect of alcohol
was found for five of the measures, the interpre-
tation of the findings with respect to the effects
of alcohol on problem-solving performance is
rather complicated. First, the fact that the study
here “attached to” the vestibular stimulation
study creates a problem, Specifically, in the
comparisons on day 1 between the alcohol first
and the alcohol second groups, the effects of the
two variables (alcohol and vestibular stimula.
tion) are confounded. The alcohol-first grouy
was exposed to vestibular stimulation prior tc
testing on day 1 whereas the alcohol-second grouy
was not. Similarly, on day 2 there is partia
confounding of the two variables in that th:
alcohol-second group was exposed to the ves
tibular stimulation for the first time on tha
day. Second, of the five significant F-ratios fo:
the alcohol effect, in only one case was the per
formance of the alcohol-second group actuall;
poorer with than without alcohol, and even ii
that case (errors on the second solution), per
formance was not significantly poorer unde
alcohol.

The simple effects of alcohol on day 1 for th
time per response measure (second solution) ar
relatively clear-cut. For this analysis, there i
both a significant effect of alcohol and a signifi
cant effect of the vestibular stimulation and/o
the placebo. The alcohol-second group responde
the fastest, the control group (placebo and ves
tibular stimulation) second fastest, and th
alcohol-first group (their alcohol day) responde
the slowest, all of these differences being signif
cant. The possibility that it was the vestibula
stimulation that produced the significant effec
on the performance of the control group make
interpretation of the day-2 findings for secon
solution errors rather difficult, Although tk
alcohol-second group differed significantly fro
the combined control and alcohol-first group
this was the first exposure of the alcohol-secon
group to the vestibular stimulation. Considerin
the performance of the control group, the in
proved performance of those subjects on day
is probably reflective of practice effects but
may also be reflective of some kind of adaptatic
to the vestibular stimulation. Thus, the greats
number of second-solution errors made on day
by the alcohol-second group relative to the oth


the correct first button would have to be pushed
again in order to continue the search for the
second button. Similarly, if at any time during
the search the red light came on, the subject had
to re-enter the partial solution he had already
discovered before he could continue the search
for the next button in the problem sequence.
Since the correct solution used each button only
once, those buttons which were included in a
partial solution were to be eliminated from the
search, The onset of the green light indicated
that the problem had been solved. Thus, if the
solution for a given problem were 3, 5, 1, 4, 2,a
subject who used the search sequence would enter
the following sequence of button pushes (an 2?
representing the onset of the red light): R, 1,
R, 2, R, 3, 4, R, 3, 5, 1, 2, Ry 3, 5, 1, 4, 2, Green
Light. After a 10-second delay, the green light
would go out, the red light would come on, and
the same problem would be presented a second
time. Thus, each problem was solved twice—
once by discovering the sequence by a trial-and-
error process through application of the search
procedure and once by re-entering the already
obtained sequence; the error light functioned the
same during the second solution as it did for the
first solution. The green light was also illumi-
nated for a 10-second interval following the
entry of the second solution. Thus, the subject
also had to remember whether the onset of the
red light meant that he was to repeat the pre-
ceding problem solution or that a new problem
was present.

The subjects were required to search for the
problem solution by trying buttons in a left-to-
right sequence; for this purpose, the left hand
button was to be considered as following the
extreme right hand button. This procedure was
chosen because it provided an easily-learned way
of simplifying and standardizing the memory
load during search. It also provided a means of
standardizing error detection during search;
specifically, the number of errors (red lights)
for a given problem can be predicted exactly for
a given problem by relating the problem solution
back to the search sequence. For example, the
sample problem shown in the preceding para-
graph should be solved with only four “errors”
if the search sequence is followed properly; of
course, it is possible to make fewer errors by
chance deviations from the search sequence at

the risk of forgetting what one has done an
thus, making redundant responses.

Responses were recorded on punch tape
means of an automatic scoring system. TI
time at which each event occurred with respe
to the beginning of the experimental session w:
recorded to the nearest 1/100 sec. The buttc
pushed, whether or not it was in the corre
sequence, and whether it was associated with +
initial or re-entered solution were also recorde
The punch tapes were then compiled and a
alyzed by computer.

Four time measures were taken separately f
the first and second solution phases. These we
mean time per response, mean time per corr
response, mean time per incorrect. response, a
mean time per solution. In addition, a me
time per problem with first and second soluti
data combined was computed.

An error measure for first solution perfor
ance was derived by taking the mean differer
between the number of incorrect responses a
the number of incorrect responses which wor
be expected if the search procedure were {
lowed correctly. Since the subject should :
make any errors during the second solution,
error measure for second solution was simply
number of incorrect responses.

C. Procedure. The 31 subjects were randor
divided into three groups; the control group }
an N of 11 and two experimental groups had
N of 10 each. One experimental group recei
alcohol on the first day of testing and the ot
received alcohol on the second day of testi
The experimental subjects were given alcoho]
the amount of 2.5 ml of 100-proof Wild Tur
bourbon or Smirnoff vodka per kg of b
weight. This is equivalent to slightly over
absolute alcohol per kg of body weight and
calculated to give a peak blood alcohol leve!
about 100 mg%. The vodka or bourbon
diluted with orange juice to a total volume
about 30 fluid ounces. Control subjects recei
a placebo of equal volume with a few drop:
rum extract added to simulate the additior
alcohol. The subjects were given 30 minute
which to drink the beverage. Six of the alco
first subjects were given bourbon and four ¥
given vodka; in the alcohol-second group,
subjects were given bourbon and six were g
vodka.


EFFECTS OF ALCOHOL ON A PROBLEM SOLVING TASK

Introduction.

In a previous study (Chiles and Jennings,
70) we found alcohol (an average blood
2ohol level of 105 mg%) to produce significant
crements in skills important to flying. Spe-
ically, both monitoring and two-dimensional
wcking performance suffered, although decre-
mts were not found in the performance of a
aple mental arithmetic task with subjects who
re given substantial practice before testing.
e tasks were performed in different combina-
ns which required time sharing, and we con-
ded that the subjects probably tended to place
iigher priority on the arithmetic task and thus
stected their performance of that task.
Carter, Jones, Simpson, and Vega (1971) re-
‘ted decrements in performance on a variety
tasks with (Breathalyzer) blood alcohol
els of 80 mg%; included were tests of short-
m memory (WAIS Digit Span and dichotic
sentation of digits), simple and choice visual
ction time, and abstracting and conceptual
lity (Shipley-Hartford). However, with
re practiced subjects, alcohol effects were
nd only on one of these tasks—3-choice reac-
1 time.
similarly, Carpenter and Ross (1959) reported
rements in short-term memory with an alcohol
2 of 1 ml/kg of body weight. (Blood alcohol
‘Is were not specified.) Again, this effect was
sely mitigated by increased practice.
‘he present study examines the effect of a
lerately high level of blood alcohol on a
ple problem-solving task. Basically, the
: required the subject to discover the correct
ience in which to push five buttons in order
urn on a green light; a red light provided
w feedback to the subject. The solution ob-
ed had to be remembered for 10 seconds and
1 re-entered. Thus, performance of the task
primarily dependent on short-term memory
perceptual-motor speed, both of which are
ortant elements in aviation operations.

II. Method.

A, Subjects, Thirty-one paid volunteer male
subjects were tested; they were college students
in their twenties who described themselves as
“moderate social drinkers.” The subjects served
concurrently in another experimental study that
involved rotational stimulation of vestibular
mechanisms. (The testing schedule in that other
experiment was such that the subjects could
serve in the problem-solving study without addi-
tional subject. costs.)

B. Apparatus, The apparatus consisted of a
small metal box (approximately 11x 18x9 cm)
on which five push buttons were mounted in a
row. The buttons were 8 mm in diameter and
were spaced with 2.4 cm between edges; they
were labeled with the numbers one through five.
The subjects were required to make all responses
with the index finger of the preferred hand.
Three indicator lights (amber, red, and green)
were mounted about 10 em above the box on a
panel in front of the subjects. The lights pro-
vided information in the following manner. At
the beginning of a problem the red light was
illuminated to indicate to the subject that he
should begin to search for the problem solution.
Whenever any button was pushed, the amber
light would come on and remain on until the
button was released; this light indicated that
the response had been registered by the pro-
gramming and scoring equipment. Coincident
with the onset of the amber light, the red light
would go out. When the subject released the
button, the red light would come back on if the
response were incorrect, but it would remain out
if the response were correct. Thus, the number-
one button for a given problem was the button
that would keep the red light out when the but-
ton was released. If the next button pushed
after finding the first correct button was the
correct second button, the red light would re-
main out; if it were not the correct. second but-
ton, the red light would be re-illuminated and