Journal o! Studies on Alcohol, Vol. 37, No. II,
1976
Codinganti VigilanceunderAlcohol RepeatedTestswith Low Concentrations ' • M. Vogel-Sprott '• SVMManY.Over /our alcohol test sessions,social drinkers' per/ormanceon a codingtaskgraduall•timproved,but vigilanceremainedunchanged.
LOW blood alcohol concentrations (BACS, 0.085 or less) the performance efficiencyof socialdrinkersis impairedon
sometypesof tasks(e.g., 1-4). In general,it seemsthat complextasks,particularlythoserequiringconsiderable learning andintellectual concentration, aremoresensitive to disruption than are relativelysimple,purelysensory tasks.Studiesyieldingthese conclusions havetypicallyemployed a "singlealcoholtest"design. Underthisprocedure, subjects arewell trainedon a task(to avoid confounding learningeffects),then they receivetheir alcoholdose and subsequently performthe taskat intervalsduringrisingand falling BACS. It seemsthat studiesexaminingthe effect of low •ACS on performance haverarely,if ever,employeda "repeatedalcohol test"designin whichsubjects are retestedat a later date,repeatingtheir alcoholdoseand experimental task.In the absence of research employing the repeatedalcoholtest procedure, little evidenceis availableto indicatewhetherthe impairmentunder low •acs in sometasksis an initial impairmentwhichdiminishes with subsequent repeatedexposure to alcohol,or whetherit is consistentlyobservedwhen drinkersare retested.In real-life situations,socialdrinkersare likely to performthe sametasks(e.g., car driving) oftenunderlow aAcs.Thus the questionof the conxThis researchwas supportedby a grant h'om the Non-Medical Use of Drugs Directorate, National Health and Welfare, Canada. The assistanceof Mrs. R. Shortt is gratefully acknowledged.
aProfessorof Psychology,University of Waterloo,.Waterloo, Ont., Canada N2L 3G1.
Receivedfor publication:26 September1975. Revision:i April 1976. 1581
1582
M. VOGEL-SPROTT
sistency of performance impairment underlow,CS hassomepractical importance.
The behavioral consequences of repeated high,CS havebeen investigated in studiesof alcoholtolerance(e.g., 5, 6, 7). Ethical
considerations preclude theuseof humans in suchresearch, for it typicallyinvolves administering large,physiologically addicting doses overa protracted timeperiod.Undertheseconditions, the behavioral disruption initiallyoeeasioned by ale0holeustomarily diminishes sothatperformance underthedrugeventually resembles the originaldrug-free behavior. Theseeffectsmightbe attributed to thedevelopment of newadaptive compensatory taskresponses, or to a reduced physiological sensitivity to alcohol oeeasioned by addiction, or to bothfactors.Thusthe interpretation of the phenomenonremainssomewhatcontroversial (e.g., 8, 9, 10). In con-
trast,interpretation of changes in behavior whenrepeated testsat low•ACSarewidelyspaced in timewouldbe simpler because any physiological factoroccasioned byaddiction couldbeexcluded fi'om consideration. In addition,suchresearchcan be conductedwith
humans, eliminating theneedto extrapolate fromanimaldata.The present study, whichemployed social drinkers, wasdesigned to examinethe degreeof disruption in performance of a well-learned taskasa functionof repeatedtestsat low ,cs. METHOD
Subjects. The subjects were 10 menvolunteers rangingin age from 19 to 28 years(mean24.4). They were paid $28.00eachfor their participation.
Apparatus. An Intoxilyzer(OmicronSystems Corporation) was em-
ployed to measure B•,cfrombreathsamples. Thisinstrument serves the samepurpose astheBreathalyzer butusesan infraredrefraction process to detectandmeasure the B•,c.The reliabilityof thismeasurement tech-
niqueis comparable to the Breathalyzer, but the Intoxilyzer hasthe advantage of displaying themeasure automatically asa digitalread-out. Task.A "coding-vigilance" (cv) taskwasemployed. Thisrequired the subjectto work on a paper-and-pencil codingtaskwhile maintainingvigilance for a signallightthatoccurred irregularly andintroduced a new coding instruction.
Thecodingcomponent of thistaskhasbeenusedpreviously to detectlow ,,c effects(11, 12) andmaybe brieflydescribed. On each trial,the subject received a page(8)• 11 inches)headedby instructionsin whicheachnumeral,from 2 to 7, was associated with an in-
struetion (e.g.,"circlecapitalletters" or "cheekoversmallletters"). The remainderof the sheetwas filled with a matrix of scrambled
CODING AND VIGILANCE
1583
lettersandnumbers.Sevenequivalentformsof the testwere constructed by changingthe heading(so that the numberswere associated with anotherinstruction),and by rearrangingthe rows of the matrix. Trials on this test were of 3~minuteduration.The subjectworked on a differentform of the test on eachtrial; codingperformance was measured by the numberof letterscorrectlycodedduringa trial. After the codingtesthasbeenwell learned,a singleadministration of a low doseof alcoholhasbeenfoundto disruptperformance (11, 12). The addedelementof "vigilance" was providedby a reaction-time apparatuswhichwas programmed to presentsix light signalsduringa 3-min codingperiod. The interval betweenthese signalsvaried from 15 to 45 seconds with a mean of 30 sec.The light signalitself was small and dim, and was placedon the subject'sdesk near the elbow of his nonpreferred hand.Sincethis was beyondhis peripheralvision, he had to look away from his codingsheetto checkfor the occurrence of the light.Eachtime he noticeda light he wasrequiredto extinguish it by pressinga buttonbesideit. He then continuedcoding. To ensurethat the subjectwould not ignorethe signalsand merely concentrateon coding,each light carried informationabout a new rule for coding.When a light went on, it meant that one of the numbered instructions in the headingof his sheethad to be ignoredso that he
mustnot codethe lettersin the matrixassociated with it. A card (3 X 4 inches)on the deskin front of the subjectindicatedwhich instruction was to be ignoredwhen eachof the six lightsoccurred.This card displayedthe sixinstruction numbersin a randomsequence and the subject was requiredto associate eachsuccessive signalduring a trial with each successive number on the card. For example,if the card displayedthe sequence7, 3, 2, 5, 6, 4 then the occurrenceof the first light would mean that all letters in the matrix associated with instruction 7 must henceforth be left blank and should not be coded. This rule would be
in effect until the secondlight occurred.At that time, coding of instruction7 would be resumed,but letters in the matrix precededby a 3 had to be left blank wheneverthey were encountered.This routine continued throughout the trial, so that at its conclusionthe subject would have received the sixth signal light and would be coding all items on the sheet except those associatedwith instructionnumber 4. A set of 21 cards was prepared, each presentingthe 6 numbersin a different order. These were used in conjunctionwith the 7 forms of the codingtask. On a given trial all subjectshad the samecard paired with the samecodingform. After 7 trials the coding forms xvouldbegin to repeat, but 21 trials would occur before the same form and card were paired. Under this procedureit was impossibleto perceive any systematicrepetition in the cv task demands. The cv task provided two measuresof behavior: (1) "Vigilance,"or speed in noticing the light signals,was measuredautomaticallyby a timer which cumulated elapsedtime between onset and offset of the six signal lights during a trial. (2) Coding efficiency xvasmeasured by countingthe number of items correctlycoded during a trial. Letter
1584
M. VOGEL-SPI•OTT
items belongingto an instructionalnumber that was left blank in accord with the light signalwere not includedin this score.Occasionally a subjectwould notice a light signalbut fail to skip the appropriate instructional unit. The coded items in this unit were considered errors
and subtractedfrom his score.If the subjectfailed to notice a light he was also penalized.Since the averagenumber of items belonging to any instructionalnumber was five, his score was reduced by this amount on the assumptionthat, on average,he would have made at
leastfive errorsby codingitems that shouldhave been skipped. Of incidentalinterestin this studywere the participants'own opinions of the effect of alcohol on their behavior. Thus on each trial of a drink-
ing test session,they were asked to estimate their BACand to evaluate
their codingefficiencyon the cv task. Performancewas judged on a 7-point rating scaleindicatingtheir opinionof their druggedbehavior relativeto their stable,drug-freebaselinecodingachievement.Opinions on the scale could range from "much better" (scored 73) to "much worse"(scored--3), with "no change"at the midpoint (scored0). The subiectused this scale prior to a ½v trial to predict the achievement he expectedto display,and he usedthe scaleagain immediatelyafter a trial to indicatethe level of performancehe thoughthe had attained. Procedure.The participantshad three Pl-hour appointmentsin the laboratorybefore beginningthe alcoholtest sessions. These visitswere conductedat weekly intervalswith two subjectsat a time. The pairing of subiectsfor their first appointmentwas determinedchiefly by mutual availability of time. Thereafter, however, the same subiectswere paired for all subsequentappointments.Over the courseof these visits each subiectcompleteda total of 21 trials of 3 min on the cv task to ensurethat it was well learned; he was also given some practice using the rating scaleto appraiseand predict his performance.In addition, he had a "taste"of an alcoholicbeveragein orderto becomefamiliar with the procedureof supplyingbreath samplesto the Intoxilyzer. Alcohol tests began a week after the familiarization appointments concluded. A total of four test sessions were administered over an 8-
week period. The first two and the last two alcoholtestswere each scheduledi week apart so that there was a 4-week interval between the first two and the last two test sessions.
Each alcohol test followed the same procedure.Two 3-min cv trials
were administeredbefore drinking began, and all subiectsreceivedan equivalentdoseof alcohol(1.98 ml of 405 ethanolper kg of body weight, mixed with an equal volume of a carbonatedbeverage). Onethird of the dose, termed "drink," was administeredat 20-min intervals,
and the subiecthad to finish his drink within 10 min. Then, 16 min after a drink was presented,he had a 3-min cv trial which was preceded and followed by his evaluationof performanceon the rating scale.This predictionand appraisal,togetherwith the cv trial, took a total of 4 min. Thus the first BACmeasureand the subiect'sestimate of his Bxcwere obtained20 min after the drinkingsession began. (Actual BxCmeasureswere never reportedto the participants. )
The drinkingprocedureand accompanying measureswere repeated during each of the next two 20-min intervals.Preliminaryinvestigation of the effectsof thesedrinksindicatedthat peak B•,cwas likely to occur 60 to 70 min after drinking had commenced.Thus, after 70 min, the subjectreceivedanother½vtrial, evaluatedhis performance,estimated his B•,c, and provided a breath sample.The same routine was subsequently repeated at 20-min intervals (i.e., 90 and 110 min into the session ). ]•ESULTS
Varianceanalysisof the BACmeasuresobtainedduringthe four
alcoholsessions revealedno significant differences (p)
.50), and
indicatedthat rising and falling BACSduring all sessions were virtually identical.The mean•AC obtainedduringsessions is shown in Figure 1.
Drug-Free CV Performance
Duringthelastfamiliarization appointment eight3-min½vtrials were given.The first two of thesewere termed"warm-up"and
"baseline," respectively. Theremaining sixtrialshadbeenscheduled according to the procedure whichwasto be followed duringthe alcoholsessions. A varianceanalysisof the codingand vigilance scoresobtainedfrom thesesixtrialsrevealedno significanttrial ef-
fects(p) .50), andindicated that performance had stabilized. .O7 .O6 .05
!
1976
Codinganti VigilanceunderAlcohol RepeatedTestswith Low Concentrations ' • M. Vogel-Sprott '• SVMManY.Over /our alcohol test sessions,social drinkers' per/ormanceon a codingtaskgraduall•timproved,but vigilanceremainedunchanged.
LOW blood alcohol concentrations (BACS, 0.085 or less) the performance efficiencyof socialdrinkersis impairedon
sometypesof tasks(e.g., 1-4). In general,it seemsthat complextasks,particularlythoserequiringconsiderable learning andintellectual concentration, aremoresensitive to disruption than are relativelysimple,purelysensory tasks.Studiesyieldingthese conclusions havetypicallyemployed a "singlealcoholtest"design. Underthisprocedure, subjects arewell trainedon a task(to avoid confounding learningeffects),then they receivetheir alcoholdose and subsequently performthe taskat intervalsduringrisingand falling BACS. It seemsthat studiesexaminingthe effect of low •ACS on performance haverarely,if ever,employeda "repeatedalcohol test"designin whichsubjects are retestedat a later date,repeatingtheir alcoholdoseand experimental task.In the absence of research employing the repeatedalcoholtest procedure, little evidenceis availableto indicatewhetherthe impairmentunder low •acs in sometasksis an initial impairmentwhichdiminishes with subsequent repeatedexposure to alcohol,or whetherit is consistentlyobservedwhen drinkersare retested.In real-life situations,socialdrinkersare likely to performthe sametasks(e.g., car driving) oftenunderlow aAcs.Thus the questionof the conxThis researchwas supportedby a grant h'om the Non-Medical Use of Drugs Directorate, National Health and Welfare, Canada. The assistanceof Mrs. R. Shortt is gratefully acknowledged.
aProfessorof Psychology,University of Waterloo,.Waterloo, Ont., Canada N2L 3G1.
Receivedfor publication:26 September1975. Revision:i April 1976. 1581
1582
M. VOGEL-SPROTT
sistency of performance impairment underlow,CS hassomepractical importance.
The behavioral consequences of repeated high,CS havebeen investigated in studiesof alcoholtolerance(e.g., 5, 6, 7). Ethical
considerations preclude theuseof humans in suchresearch, for it typicallyinvolves administering large,physiologically addicting doses overa protracted timeperiod.Undertheseconditions, the behavioral disruption initiallyoeeasioned by ale0holeustomarily diminishes sothatperformance underthedrugeventually resembles the originaldrug-free behavior. Theseeffectsmightbe attributed to thedevelopment of newadaptive compensatory taskresponses, or to a reduced physiological sensitivity to alcohol oeeasioned by addiction, or to bothfactors.Thusthe interpretation of the phenomenonremainssomewhatcontroversial (e.g., 8, 9, 10). In con-
trast,interpretation of changes in behavior whenrepeated testsat low•ACSarewidelyspaced in timewouldbe simpler because any physiological factoroccasioned byaddiction couldbeexcluded fi'om consideration. In addition,suchresearchcan be conductedwith
humans, eliminating theneedto extrapolate fromanimaldata.The present study, whichemployed social drinkers, wasdesigned to examinethe degreeof disruption in performance of a well-learned taskasa functionof repeatedtestsat low ,cs. METHOD
Subjects. The subjects were 10 menvolunteers rangingin age from 19 to 28 years(mean24.4). They were paid $28.00eachfor their participation.
Apparatus. An Intoxilyzer(OmicronSystems Corporation) was em-
ployed to measure B•,cfrombreathsamples. Thisinstrument serves the samepurpose astheBreathalyzer butusesan infraredrefraction process to detectandmeasure the B•,c.The reliabilityof thismeasurement tech-
niqueis comparable to the Breathalyzer, but the Intoxilyzer hasthe advantage of displaying themeasure automatically asa digitalread-out. Task.A "coding-vigilance" (cv) taskwasemployed. Thisrequired the subjectto work on a paper-and-pencil codingtaskwhile maintainingvigilance for a signallightthatoccurred irregularly andintroduced a new coding instruction.
Thecodingcomponent of thistaskhasbeenusedpreviously to detectlow ,,c effects(11, 12) andmaybe brieflydescribed. On each trial,the subject received a page(8)• 11 inches)headedby instructionsin whicheachnumeral,from 2 to 7, was associated with an in-
struetion (e.g.,"circlecapitalletters" or "cheekoversmallletters"). The remainderof the sheetwas filled with a matrix of scrambled
CODING AND VIGILANCE
1583
lettersandnumbers.Sevenequivalentformsof the testwere constructed by changingthe heading(so that the numberswere associated with anotherinstruction),and by rearrangingthe rows of the matrix. Trials on this test were of 3~minuteduration.The subjectworked on a differentform of the test on eachtrial; codingperformance was measured by the numberof letterscorrectlycodedduringa trial. After the codingtesthasbeenwell learned,a singleadministration of a low doseof alcoholhasbeenfoundto disruptperformance (11, 12). The addedelementof "vigilance" was providedby a reaction-time apparatuswhichwas programmed to presentsix light signalsduringa 3-min codingperiod. The interval betweenthese signalsvaried from 15 to 45 seconds with a mean of 30 sec.The light signalitself was small and dim, and was placedon the subject'sdesk near the elbow of his nonpreferred hand.Sincethis was beyondhis peripheralvision, he had to look away from his codingsheetto checkfor the occurrence of the light.Eachtime he noticeda light he wasrequiredto extinguish it by pressinga buttonbesideit. He then continuedcoding. To ensurethat the subjectwould not ignorethe signalsand merely concentrateon coding,each light carried informationabout a new rule for coding.When a light went on, it meant that one of the numbered instructions in the headingof his sheethad to be ignoredso that he
mustnot codethe lettersin the matrixassociated with it. A card (3 X 4 inches)on the deskin front of the subjectindicatedwhich instruction was to be ignoredwhen eachof the six lightsoccurred.This card displayedthe sixinstruction numbersin a randomsequence and the subject was requiredto associate eachsuccessive signalduring a trial with each successive number on the card. For example,if the card displayedthe sequence7, 3, 2, 5, 6, 4 then the occurrenceof the first light would mean that all letters in the matrix associated with instruction 7 must henceforth be left blank and should not be coded. This rule would be
in effect until the secondlight occurred.At that time, coding of instruction7 would be resumed,but letters in the matrix precededby a 3 had to be left blank wheneverthey were encountered.This routine continued throughout the trial, so that at its conclusionthe subject would have received the sixth signal light and would be coding all items on the sheet except those associatedwith instructionnumber 4. A set of 21 cards was prepared, each presentingthe 6 numbersin a different order. These were used in conjunctionwith the 7 forms of the codingtask. On a given trial all subjectshad the samecard paired with the samecodingform. After 7 trials the coding forms xvouldbegin to repeat, but 21 trials would occur before the same form and card were paired. Under this procedureit was impossibleto perceive any systematicrepetition in the cv task demands. The cv task provided two measuresof behavior: (1) "Vigilance,"or speed in noticing the light signals,was measuredautomaticallyby a timer which cumulated elapsedtime between onset and offset of the six signal lights during a trial. (2) Coding efficiency xvasmeasured by countingthe number of items correctlycoded during a trial. Letter
1584
M. VOGEL-SPI•OTT
items belongingto an instructionalnumber that was left blank in accord with the light signalwere not includedin this score.Occasionally a subjectwould notice a light signalbut fail to skip the appropriate instructional unit. The coded items in this unit were considered errors
and subtractedfrom his score.If the subjectfailed to notice a light he was also penalized.Since the averagenumber of items belonging to any instructionalnumber was five, his score was reduced by this amount on the assumptionthat, on average,he would have made at
leastfive errorsby codingitems that shouldhave been skipped. Of incidentalinterestin this studywere the participants'own opinions of the effect of alcohol on their behavior. Thus on each trial of a drink-
ing test session,they were asked to estimate their BACand to evaluate
their codingefficiencyon the cv task. Performancewas judged on a 7-point rating scaleindicatingtheir opinionof their druggedbehavior relativeto their stable,drug-freebaselinecodingachievement.Opinions on the scale could range from "much better" (scored 73) to "much worse"(scored--3), with "no change"at the midpoint (scored0). The subiectused this scale prior to a ½v trial to predict the achievement he expectedto display,and he usedthe scaleagain immediatelyafter a trial to indicatethe level of performancehe thoughthe had attained. Procedure.The participantshad three Pl-hour appointmentsin the laboratorybefore beginningthe alcoholtest sessions. These visitswere conductedat weekly intervalswith two subjectsat a time. The pairing of subiectsfor their first appointmentwas determinedchiefly by mutual availability of time. Thereafter, however, the same subiectswere paired for all subsequentappointments.Over the courseof these visits each subiectcompleteda total of 21 trials of 3 min on the cv task to ensurethat it was well learned; he was also given some practice using the rating scaleto appraiseand predict his performance.In addition, he had a "taste"of an alcoholicbeveragein orderto becomefamiliar with the procedureof supplyingbreath samplesto the Intoxilyzer. Alcohol tests began a week after the familiarization appointments concluded. A total of four test sessions were administered over an 8-
week period. The first two and the last two alcoholtestswere each scheduledi week apart so that there was a 4-week interval between the first two and the last two test sessions.
Each alcohol test followed the same procedure.Two 3-min cv trials
were administeredbefore drinking began, and all subiectsreceivedan equivalentdoseof alcohol(1.98 ml of 405 ethanolper kg of body weight, mixed with an equal volume of a carbonatedbeverage). Onethird of the dose, termed "drink," was administeredat 20-min intervals,
and the subiecthad to finish his drink within 10 min. Then, 16 min after a drink was presented,he had a 3-min cv trial which was preceded and followed by his evaluationof performanceon the rating scale.This predictionand appraisal,togetherwith the cv trial, took a total of 4 min. Thus the first BACmeasureand the subiect'sestimate of his Bxcwere obtained20 min after the drinkingsession began. (Actual BxCmeasureswere never reportedto the participants. )
The drinkingprocedureand accompanying measureswere repeated during each of the next two 20-min intervals.Preliminaryinvestigation of the effectsof thesedrinksindicatedthat peak B•,cwas likely to occur 60 to 70 min after drinking had commenced.Thus, after 70 min, the subjectreceivedanother½vtrial, evaluatedhis performance,estimated his B•,c, and provided a breath sample.The same routine was subsequently repeated at 20-min intervals (i.e., 90 and 110 min into the session ). ]•ESULTS
Varianceanalysisof the BACmeasuresobtainedduringthe four
alcoholsessions revealedno significant differences (p)
.50), and
indicatedthat rising and falling BACSduring all sessions were virtually identical.The mean•AC obtainedduringsessions is shown in Figure 1.
Drug-Free CV Performance
Duringthelastfamiliarization appointment eight3-min½vtrials were given.The first two of thesewere termed"warm-up"and
"baseline," respectively. Theremaining sixtrialshadbeenscheduled according to the procedure whichwasto be followed duringthe alcoholsessions. A varianceanalysisof the codingand vigilance scoresobtainedfrom thesesixtrialsrevealedno significanttrial ef-
fects(p) .50), andindicated that performance had stabilized. .O7 .O6 .05
!
