Psychological Reports, 1990, 67, 643-650.
@ Psychological Reports 1990
EFFECTS OF ALCOHOL O N PROLONGED COGNITIVE PERFORMANCE MEASURED W I T H STROOP'S COLOR WORD TEST '.* ROLAND GUSTAFSON AND
HAKAN KALLMEN
University of ~ r e b r oSweden , Summary.-24 men and 24 women were randomly assigned in equal numbers to an Alcohol group, a Placebo group, or a Control group. The alcohol dose was 1.0 ml of 100% alcohol/kg of body weight. Subjects were tested three consecutive times using Stroop's Color Word Test. The dependent measures were total time needed to complete the test, number of errors made and number of hesitations. Data were grouped into three blocks of 100 words. Results indicated that number of hesitations was too insensitive a measure to yield any significant effects. On the two first measures alcohol had a detrimental effect in that the Alcohol group needed more time to complete the test and made more errors than the Placebo group. There was also a significant interaction of alcohol dose by sex by blocks on both these measures, indicating that the detrimental effect of alcohol over time was restricted to women. Different implications of the results were discussed.
Moderate doses of alcohol usually have detrimental effects on the performance of cognitive tasks. The ability to integrate and interpret incomplete pictures is impaired under alcohol, which can be understood in psychoanalytic terms as an indication of a reduced secondary process functioning (Gustafson & Killmen, 1989a, 1989b). The attention-allocating system also seems to be sensitive to alcohol intoxication (Chiles & Jennings, 1970), so complex tasks demanding divided attention are more difficult to perform under alcohol intoxication than are simple tasks (Moskowitz, 1973; Gustafson, 1986b). Under intoxication, the attention-allocating system easily becomes overloaded, and as a consequence attention is narrowed to what is judged to be the most central and salient features of a situation (Taylor & Leonard, 1983). I t seems quite clear that alcohol may impair cognitive functioning. The performance of various tasks under the influence of alcohol may also be affected by a process of cognitive compensation. I t is assumed that subjects can be motivated, for example, by social norms, not to show any signs of intoxication or reduced functioning under alcohol and so make a more or less conscious cognitive effort to counteract the detrimental effects of alcohol. Williams, Golman, and Williams (1981) reported that subjects apparently compensated for alcohol-induced deterioration on cognitive tasks 'This study was supported by rants from The Swedish Delegation for Social Research (DSF), $tockholm, and from ~ ~ s t e m b o k a ~ eFoundation t's for Alcohol Research (SFAI, Stockholm. Ad,&ess requests for reprints to Dr. Roland Gustafson, Department of Psychology, Univenity of Orebro, Box 923, S-701 30, Orebro, Sweden.
like letter cancellation, digit span and Raven's Matrices. This effect was related to the cognitive complexity of the task. I n a previous study no effects were found for a moderate dose of alcohol for women and only small effects for men on three dependent measures related to Stroop's Color Word Test (Gustafson & Klillmkn, 1990). This test is based on the performance of a complex cognitive task, namely, the ability to separate a text dimension from a color dimension and only report the latter. Intoxicated women did not use more time to complete the test, did not make more errors, and did not hesitate more than did sober women. Intoxicated men needed more time than sober men but were not impaired with respect to the other two dependent measures. This was a surprising result and a tentative interpretation was given in terms of cognitive compensation. Under what circumstances is it possible to compensate for alcohol effects in the above sense? The period of time seems to be an important variable. I n the previous study the time interval of testing was less than 2 min. (Gustafson & KdmCn, 1990). In a series of vigilance experiments extended over 30 min, with simple R T as the dependent variable, no significant effects of alcohol emerged during the first 5 min. of testing, whereas the impairing effects were rather dramatic after roughly 10 min. of testing (Gustafson, 1986a). For a complex cognitive task this time interval is hypothesized to be shorter than 10 rnin. but longer than 2 min. The purpose of the present study was to explore whether it is possible to compensate for the impairing effect of alcohol on the performance of a complex cognitive task over periods of time extended above 2 to 3 min. Cognitive performance was measured using Stroop's Color Word Test to attain comparabdity with the previous study (Gustafson & Klillmkn, 1990).
Subjects and Alcohol Twenty-four men and 24 women (mean age = 27.7, SD = 7.6) participated in the study. The subjects were randomly assigned to three experimental groups, namely, an Alcohol group (drank alcohol/informed alcohol), a Placebo group (drank tonic/informed alcohol), and a Control group (drank tonic/informed tonic). There were eight men and eight women in each group. All subjects were students at the University of drebro and were solicited through flyers distributed in class. All subjects were moderate social drinkers according to their own ratings. The Alcohol group received a drink containing 1.0 rnl of 100% alcohol/kg of body weight served in the form of Swedish commercial, colorless vodka (Absolut Vodka) containing 40% by volume. The drink was mixed with an equal amount of tonic water (Schweppes). The Placebo group re-
ALCOHOL, COGNITIVE PERFORMANCE
645
ceived an equal amount of liquid, that is, a drink containing 5 ml of tonic/kg mixed with 10 ml of vodka extract (Simpson). A few rmllilitres of vodka were floated on top of the drink and a few drops were added to the edge of the glass to give a smell and taste of alcohol. The subjects in this group were informed that the drink contained alcohol. The Control group received 5 ml of tonic/kg body weight and were informed that the dLink-contained only tonic water.
Dependent Variables Stroop's Color Word Test was used to test for the effects of alcohol (Stroop, 1935). This test consists of a sheet of paper on which are printed 100 words. The words are ordered in 10 lines with 10 words on each line. Each word is a color name, red, blue, green, or yellow, which name is printed in an incongruent color. That is, the word "Blue" may be printed in green, red, or yellow. The order of both colors and printed words is random. The test contains one text dimension and one color dimension, and the task of the subject is to separate the two dimensions from each other and only report one, namely, the printed color of the word. The subject had to repeat the test three times without a pause. Subjects therefore reported a total of 300 words. The Color Word Test can be scored for three separate dependent variables. These are (a) total time needed to complete the test, (b) number of incorrect responses, and (c) number of hesitations. Total time is defined as the time taken by the subject to report all the colors of the 100 words. Number of incorrect reports is defined as the total number of times the subject reports an incorrect color by being influenced by the actual letters, and number of hesitations is defined as the total number of times the subject deviates from h s individual reading rhythm with more than 1 sec. before reporting the color. The responses were recorded on a tape recorder and later coded for the three dependent measures. To obtain a reliable measure of hesitations, first all deviations from the individual reading rhythm were marked and then each one was carefully timed in relation to the one second criterion. All responses were grouped into three blocks of 100 words. Subjects also had to fill out two questionnaires. The first was Taylor's Manifest Anxiety Scale (Taylor, 1953) and the second a modified version of Rotter's Internal-External Scale (Rotter, 1966). The former scale measures the subject's state of anxiety and the latter the subject's here-and-now feeling of whether his locus of control is experienced as inside or outside himself.
Procedure O n arrival at the laborabory the subjects were first asked to fill out a questionnaire focused on their alcohol drinlung habits. Then each subject was weighed and the appropriate drink was mixed and served. Subjects were
646
R. GUSTAFSON & H.
KALLMEN
asked to drink slowly and to finish the drink within 15 min. During this time subjects filled out the two previously mentioned questionnaires. After 15 min. of drinking and an adltional 15 min. of waiting for the alcohol to be fully absorbed, the Color Word Test was administered. The whole session took about 45 min. to complete. Each session was ended by a thorough debriefing interview. Careful instructions were given to alcohol-drinking subjects, and no subject was sent home before due precaution had been taken.
RESULTS Blood Alcohol Levels (BALs) The mean blood alcohol levels (BALs) calculated over sexes were measured immediately before the Color Word Test 0.083% (SD = 0.032) and immediately after the test 0.078% (SD = 0.023). A t test for dependent samples indicated no significant difference (t,, = .89). Since women tend to get higher BALs than men after drinking the same dose of alcohol in ml/kg body weight (Frezza, Di Padova, Pozzato, Terpin, Baraona, & Lieber, 1990), the corresponding values were also calculated separately for men and women. The BALs for women were 0.096% (SD = 0.024) and 0.096% (SD = 0.011) and for men 0.070% (SD = 0.036) and 0.061% (SD = 0.019), respectively. Separate one-way analyses of variance yielded a significant difference between men and women after the test (F,,,, = 21.15, p < .001) but not before the test (F,,,, = 2.86). Women were tested under higher peak blood alcohol levels than were men. Questionnaires A two-way analysis of variance applied to the manifest anxiety scale yielded no significant main effects either for alcohol dose (F,,,, = 1.41) or sex (F,,,, = 1.47). Neither were the main effects of alcohol dose (F2,42= 1.81) and of sex (F,,,, = .86) significant for locus of control. No interactions for these scales indicated any significant differences. Dependent Measures Total time to complete.-An analysis of variance for repeated measures indicated that the main effect of alcohol dose fell just short of significance (F,,,, = 2.86, p < .07). A univariate follow-up test showed, however, that the Alcohol group (M= 125.00 sec. per block; SD = 11.47) used significantly longer time than the Placebo group (M = 106.1 sec. per block; SD = 6.57) to complete the test (F,,,, = 5.63, p
@ Psychological Reports 1990
EFFECTS OF ALCOHOL O N PROLONGED COGNITIVE PERFORMANCE MEASURED W I T H STROOP'S COLOR WORD TEST '.* ROLAND GUSTAFSON AND
HAKAN KALLMEN
University of ~ r e b r oSweden , Summary.-24 men and 24 women were randomly assigned in equal numbers to an Alcohol group, a Placebo group, or a Control group. The alcohol dose was 1.0 ml of 100% alcohol/kg of body weight. Subjects were tested three consecutive times using Stroop's Color Word Test. The dependent measures were total time needed to complete the test, number of errors made and number of hesitations. Data were grouped into three blocks of 100 words. Results indicated that number of hesitations was too insensitive a measure to yield any significant effects. On the two first measures alcohol had a detrimental effect in that the Alcohol group needed more time to complete the test and made more errors than the Placebo group. There was also a significant interaction of alcohol dose by sex by blocks on both these measures, indicating that the detrimental effect of alcohol over time was restricted to women. Different implications of the results were discussed.
Moderate doses of alcohol usually have detrimental effects on the performance of cognitive tasks. The ability to integrate and interpret incomplete pictures is impaired under alcohol, which can be understood in psychoanalytic terms as an indication of a reduced secondary process functioning (Gustafson & Killmen, 1989a, 1989b). The attention-allocating system also seems to be sensitive to alcohol intoxication (Chiles & Jennings, 1970), so complex tasks demanding divided attention are more difficult to perform under alcohol intoxication than are simple tasks (Moskowitz, 1973; Gustafson, 1986b). Under intoxication, the attention-allocating system easily becomes overloaded, and as a consequence attention is narrowed to what is judged to be the most central and salient features of a situation (Taylor & Leonard, 1983). I t seems quite clear that alcohol may impair cognitive functioning. The performance of various tasks under the influence of alcohol may also be affected by a process of cognitive compensation. I t is assumed that subjects can be motivated, for example, by social norms, not to show any signs of intoxication or reduced functioning under alcohol and so make a more or less conscious cognitive effort to counteract the detrimental effects of alcohol. Williams, Golman, and Williams (1981) reported that subjects apparently compensated for alcohol-induced deterioration on cognitive tasks 'This study was supported by rants from The Swedish Delegation for Social Research (DSF), $tockholm, and from ~ ~ s t e m b o k a ~ eFoundation t's for Alcohol Research (SFAI, Stockholm. Ad,&ess requests for reprints to Dr. Roland Gustafson, Department of Psychology, Univenity of Orebro, Box 923, S-701 30, Orebro, Sweden.
like letter cancellation, digit span and Raven's Matrices. This effect was related to the cognitive complexity of the task. I n a previous study no effects were found for a moderate dose of alcohol for women and only small effects for men on three dependent measures related to Stroop's Color Word Test (Gustafson & Klillmkn, 1990). This test is based on the performance of a complex cognitive task, namely, the ability to separate a text dimension from a color dimension and only report the latter. Intoxicated women did not use more time to complete the test, did not make more errors, and did not hesitate more than did sober women. Intoxicated men needed more time than sober men but were not impaired with respect to the other two dependent measures. This was a surprising result and a tentative interpretation was given in terms of cognitive compensation. Under what circumstances is it possible to compensate for alcohol effects in the above sense? The period of time seems to be an important variable. I n the previous study the time interval of testing was less than 2 min. (Gustafson & KdmCn, 1990). In a series of vigilance experiments extended over 30 min, with simple R T as the dependent variable, no significant effects of alcohol emerged during the first 5 min. of testing, whereas the impairing effects were rather dramatic after roughly 10 min. of testing (Gustafson, 1986a). For a complex cognitive task this time interval is hypothesized to be shorter than 10 rnin. but longer than 2 min. The purpose of the present study was to explore whether it is possible to compensate for the impairing effect of alcohol on the performance of a complex cognitive task over periods of time extended above 2 to 3 min. Cognitive performance was measured using Stroop's Color Word Test to attain comparabdity with the previous study (Gustafson & Klillmkn, 1990).
Subjects and Alcohol Twenty-four men and 24 women (mean age = 27.7, SD = 7.6) participated in the study. The subjects were randomly assigned to three experimental groups, namely, an Alcohol group (drank alcohol/informed alcohol), a Placebo group (drank tonic/informed alcohol), and a Control group (drank tonic/informed tonic). There were eight men and eight women in each group. All subjects were students at the University of drebro and were solicited through flyers distributed in class. All subjects were moderate social drinkers according to their own ratings. The Alcohol group received a drink containing 1.0 rnl of 100% alcohol/kg of body weight served in the form of Swedish commercial, colorless vodka (Absolut Vodka) containing 40% by volume. The drink was mixed with an equal amount of tonic water (Schweppes). The Placebo group re-
ALCOHOL, COGNITIVE PERFORMANCE
645
ceived an equal amount of liquid, that is, a drink containing 5 ml of tonic/kg mixed with 10 ml of vodka extract (Simpson). A few rmllilitres of vodka were floated on top of the drink and a few drops were added to the edge of the glass to give a smell and taste of alcohol. The subjects in this group were informed that the drink contained alcohol. The Control group received 5 ml of tonic/kg body weight and were informed that the dLink-contained only tonic water.
Dependent Variables Stroop's Color Word Test was used to test for the effects of alcohol (Stroop, 1935). This test consists of a sheet of paper on which are printed 100 words. The words are ordered in 10 lines with 10 words on each line. Each word is a color name, red, blue, green, or yellow, which name is printed in an incongruent color. That is, the word "Blue" may be printed in green, red, or yellow. The order of both colors and printed words is random. The test contains one text dimension and one color dimension, and the task of the subject is to separate the two dimensions from each other and only report one, namely, the printed color of the word. The subject had to repeat the test three times without a pause. Subjects therefore reported a total of 300 words. The Color Word Test can be scored for three separate dependent variables. These are (a) total time needed to complete the test, (b) number of incorrect responses, and (c) number of hesitations. Total time is defined as the time taken by the subject to report all the colors of the 100 words. Number of incorrect reports is defined as the total number of times the subject reports an incorrect color by being influenced by the actual letters, and number of hesitations is defined as the total number of times the subject deviates from h s individual reading rhythm with more than 1 sec. before reporting the color. The responses were recorded on a tape recorder and later coded for the three dependent measures. To obtain a reliable measure of hesitations, first all deviations from the individual reading rhythm were marked and then each one was carefully timed in relation to the one second criterion. All responses were grouped into three blocks of 100 words. Subjects also had to fill out two questionnaires. The first was Taylor's Manifest Anxiety Scale (Taylor, 1953) and the second a modified version of Rotter's Internal-External Scale (Rotter, 1966). The former scale measures the subject's state of anxiety and the latter the subject's here-and-now feeling of whether his locus of control is experienced as inside or outside himself.
Procedure O n arrival at the laborabory the subjects were first asked to fill out a questionnaire focused on their alcohol drinlung habits. Then each subject was weighed and the appropriate drink was mixed and served. Subjects were
646
R. GUSTAFSON & H.
KALLMEN
asked to drink slowly and to finish the drink within 15 min. During this time subjects filled out the two previously mentioned questionnaires. After 15 min. of drinking and an adltional 15 min. of waiting for the alcohol to be fully absorbed, the Color Word Test was administered. The whole session took about 45 min. to complete. Each session was ended by a thorough debriefing interview. Careful instructions were given to alcohol-drinking subjects, and no subject was sent home before due precaution had been taken.
RESULTS Blood Alcohol Levels (BALs) The mean blood alcohol levels (BALs) calculated over sexes were measured immediately before the Color Word Test 0.083% (SD = 0.032) and immediately after the test 0.078% (SD = 0.023). A t test for dependent samples indicated no significant difference (t,, = .89). Since women tend to get higher BALs than men after drinking the same dose of alcohol in ml/kg body weight (Frezza, Di Padova, Pozzato, Terpin, Baraona, & Lieber, 1990), the corresponding values were also calculated separately for men and women. The BALs for women were 0.096% (SD = 0.024) and 0.096% (SD = 0.011) and for men 0.070% (SD = 0.036) and 0.061% (SD = 0.019), respectively. Separate one-way analyses of variance yielded a significant difference between men and women after the test (F,,,, = 21.15, p < .001) but not before the test (F,,,, = 2.86). Women were tested under higher peak blood alcohol levels than were men. Questionnaires A two-way analysis of variance applied to the manifest anxiety scale yielded no significant main effects either for alcohol dose (F,,,, = 1.41) or sex (F,,,, = 1.47). Neither were the main effects of alcohol dose (F2,42= 1.81) and of sex (F,,,, = .86) significant for locus of control. No interactions for these scales indicated any significant differences. Dependent Measures Total time to complete.-An analysis of variance for repeated measures indicated that the main effect of alcohol dose fell just short of significance (F,,,, = 2.86, p < .07). A univariate follow-up test showed, however, that the Alcohol group (M= 125.00 sec. per block; SD = 11.47) used significantly longer time than the Placebo group (M = 106.1 sec. per block; SD = 6.57) to complete the test (F,,,, = 5.63, p
