The Journal of General Psychology, 1975, 02, 53-58.
THE RELATIONSHIP BETWEEN EMOTIONALITY AND DOMINANCE IN T H E HOODED RAT* Department of Psychology, Georgetown University
ROBERTs. RUSKIN,GREGORYG . DAVIS,AND ALEX DEPERALTA,JR. SUMMARY Hooded rodents were tested in an emotionality condition and two competitive “dominance” conditions. It was found that stable rankings of subjects within the test groups could be established for each of the three conditions. Significant negative correlations were also found between a subject’s “emotionality” ranking in a group and his ranking in the group in relation to either condition of competitive dominance, while a significant positive correlation was found between a subject’s ranking in both of the competitive dominance conditions. These data are taken as evidence for a debilitating effect of high emotionality on one’s success in competition.
INTRODUCTION Past research has noted studies involving either dominance or emotion hierarchies (lo), none has attempted to study the relationship, if any, between the two. Our goal is to determine the relationship between two types of competitive dominance and emotionality. A.
1. Emotion Prior research on emotionality in rodents has provided us with wellestablished measures. The procedures and methods for determining measures of emotion were provided in two studies: Corman and Biondo ( 5 ) and Singh and Maki (14). These studies have provided evidence that different emotions can be the result of pretesting factors. Field testing for emotionality is accomplished by employing standard measures in the open field, such as the number of squares traversed, latency in the starting squares, defecation rate, etc. Emotionality in rats has been found to be largely a function
* Received in the Editorial Office, Provincetown, Massachusetts, on February 7, 1974. Copyright, 1975, by The Journal Press. 53
54
JOURNAL OF GENERAL PSYCHOLOGY
of early enironmental variables, such as early handling and isolation (2, 15). Threfore, emotionality ratings can be viewed as having been the result of factors preceding experimentation. Different aspects of emotionality have been studied to determine its etiology and to seek relationships to other forms of behavior (14). In this study we attempted to correlate it to dominance and have neglected its etiology on the assumption that it does exist and hence can be adequately measured. 2 . Dominance Dominance studies have been abundant, centering upon various aspects of the concept in order to compile a complete repertoire of the behaviors and other factors which may influence it. Procedures and measures have been secured mainly from studies by Boice et al. (3, Ruskin and Corman (9) and Ward and Gerall (15). Measures for our study included latency, nose-poke, and pellet competition. These measures have been proven highly reliable in prior research (12). Studies have found that different tests of dominance may be largely determined by the specific competitive situation. For example, dominance in one set of measures, such as between the competitive running tube and single food pellet competition, have shown a negative correlation (6), while speed in the running tube has shown a positive correlation (4). In this study, therefore, we have limited our competitive measures to only food-related competition, to eliminate the effect of situational factors.
B.
METHOD
1. Subjects
The subjects were 42 black-white hooded male rats, 30 days of age at the beginning of testing. All subjects were randomly divided into seven groups of six subjects each and were handled for 14 consecutive days by the experimenters in order to insure their docility and to provide optimal and constant treatment (1, 8). Immediately upon weaning, each subject was placed into a separate cage of equal size (7) constructed of metal which allowed free access to water at all times. During Phase I, emotionality testing, subjects were given an unlimited supply of food; during Phase 11, competitive testing, subjects were placed on 24-hour food deprivation but allowed free access to water at all times. 2. Apparatus An open field apparatus constructed of a masonite floor measuring 45 X 45 inches and wooden walls 24 inches high was employed during testing for
ROBERT S. RUSKIN ET AL.
55
emotionality. The floor area was divided into 25 equal parts identified by 9 x 9 inch black tiles. In addition, three zones were defined as (a) outside or peripheral squares, (b) center squares (all squares except the peripheral and white squares), and (c) the white square which was the actual center of the open field. The walls and starting box were painted gray. The open field apparatus was situated to allow direct viewing through a one-way mirror and concurrent videotaping. A Sony videotape apparatus, television monitor, and camera were used during testing. The television monitor allowed the experimenters to score all relevant behaviors accurately, utilizing replays if necessary. A “nose-poke” apparatus was included during Phase 11. The nose-poke was 12 x 12 inches, with an access hole 1% inches in diameter to Noyes food pellets which were delivered through a metal tube and onto a magazine tray behind the opening. The size and nature of the hole limited the feeding to only one rat at any given time. 3 . Procedure Phase Z: Phase I consisted of obtaining emotionality measures including activity, latency, and locale measures. Latency was defined as the time the subject spent before leaving the starting square. Activity was defined as the total number of squares traversed during each three-minute trial. Squares were counted as being traversed when the subject actually touched an adjacent square with both front paws. Locale measures were defined as the time subjects spent in each of the three zones: the outer squares, the “center” black squares, and the white square in the exact center of the apparatus. Each subject was tested during three-minute trials once a day for 20 consecutive days. The subject-testing sequence was randomized to control for order-effects. Testing was conducted during the same time period each day so that consistency with the subject’s circadian rhythm would not be interrupted. b. Phase ZZ: All subjects were placed on 24-hour deprivation schedules and tested with each of its “group members” assigned in Phase I. This phase included two different competitive situations. One was a dominance test employing single-pellet competition. Two rats were placed in the open field apparatus and competed for a single large food pellet which was originally placed on the white center square. The “winner” of each trial was operationally defined as that subject (of each competing pair) which had the highest latency in possession of the food pellet. All subjects were concurrently tested in a nose-poke apparatus, and the a.
56
JOURNAL OF GENERAL PSYCHOLOGY
complete procedure is described in detail in Ruskin and Corman (11). Round-robin pairings in the nose-poke or “limited access” condition were randomized with single pellet testing in order to eliminate any sequential effects of testing. Two standardized nose-poke measures-number of nose-poke responses per competitor and the total time in nose-poke opening-were recorded, and winners were determined on the basis of those animals scoring highest in both measures. Before testing in the nose-poke, each subject was allowed to individually “overlearn” nose-poke responding. After each daily experimental session, all subjects were given access to food ad lib for 60 minutes. Testing in both conditions was completely randomized with respect to both the competition situation employed and the pairs of subjects competing in each trial. Testing continued each day until all subjects had been paired with all other members of its group in both competitive situations.
C. RESULTS AND DISCUSSION Subjects in each group were ranked daily from highest (most emotional) to lowest (least emotional) on the basis of the cumulative scores in each of the three measures of emotionality. Animals ranking highest in emotionality were assigned a rank of “1,” next highest animal a “2,” and so on through number “6” in each group. Coefficients of concordance were computed over the 20 test days for the emotionality condition and for both competitive situations. These results are presented in Table 1. It is interesting to note that six of the seven groups show significant coefficients in the emotionality (Phase I) condition, six of the seven groups show significant coefficients in the single pellet “dominance” condition of TABLE 1 SIGNIFICANCE POINTS(S) FOR THE COEFFICIENT ON CONCORDANCE (W) I N THE EMOTIONALITY, LIMITEDACCESSDOMINANCE AND SINGLE-PELLET DOMINANCE CONDITIONS GrOUDS
Emotionality
Limited Access Dominance
Single-Pellet Dominance
1 2 3 4 5 6
897.1 774.6 634.3 940.0 873.6 826.2 893.4
780.3 813.4 829.6 796.5 831.4 908.7 872.8
793.2 801.4 921.6 880.7 835.5 751.0 789.9
7
Note: Number of subjects per group = 6; Number of days tested = 20; S
=
764.4, p
< .05.
57
ROBERT S. RUSKIN ET AL.
Phase II, and all seven groups show significant coefficients in the limited access nose-poke condition. The high degree of concordance in the two “dominance” conditions supports previous research (13). The degree of concordance in the emotionality ranking over the days gives evidence for a highly stable phenomenon. This evidence is augmented by the fact that the absolute scores on each of the emotionality measures when reviewed decreased over trials with every subject, but subject’s emotionality rankings relative to other members in the group stayed virtually the same. The number of “wins” of each subject over the entire 20 day test period was then computed for each of the emotionality and two competitive conditions. Each subject could receive a maximum total of 100 (five possible wins over all other group members daily times 20 test days per test condition) for the emotionality, single pellet competitive, or limited access competitive conditions. The minimum total number of wins was zero for each condition. A Pearson product-moment correlation was then determined between the number of wins in each test condition, and these results appear in Table 2. The results indicate that a subject’s emotionality correlates significantly with both “dominance” conditions. Moreover these data show that the higher the emotionality of a subject, the lower the subject’s ranking on either test of competitive dominance. It is interesting to note that this relationship is slightly more apparent between the single pellet competitive condition and the emotionality condition. One possible explanation for this slight although noticeable difference may simply lie in the fact that single pellet competition requires not only aggressive behavior from the competition but also a variety of different and rapidly developed responses, such as running with the pellet, sparring, posturing, etc. Animals who
PEARSON
TABLE 2 PRODUCT-MOMENT CORRELATIONS (r) BETWEENEMOTIONALITY AND SINGLEPELLETAND LIMITEDACCESSCOMPETITIVE DOMINANCE
Condition Emotionality Single-Pellet Dominance Limited Access Dominance
Emotionality 1.000
Single-Pellet Dominance
Limited Access Dominance
-.424 1.000
-.376 ,530
Note: df = 40; p < .01, r = ,393; p < .05, r = ,304.
1.OOO
58
JOURNAL OF GENERAL PSYCHOLOGY
exhibit rigid posturings and general lack of activity in the open-field apparatus because of extreme emotionality would not therefore be likely to exhibit the behaviors necessary for success in single-pellet competition. The data show a significant positive relationship between those subjects who rank highly in competition for single-pellets of food and those subjects who rank highly in limited access competition. These results lend support to similar previous findings (13) in which these competitive conditions were compared. These data indicate that rodents with high levels of emotionality tend to do poorly in the competitive conditions tested. The extent to which these results can be generalized to other competitive situations or test apparatus should certainly be the subject of future research in this area. REFERENCES 1. 2.
3. 4.
5.
BECKER,G. Dominance-subordination polarity in early-handled and nonhandled rats. Psychon. S c i . , 1968, 11(3), 115-116. BECKER,G., & GERARD,E. Early-handling and social-rearing effects on dominancesubordination behavior in the adult rat. Psychon. Sci., 1969, l y l ) , 27-28. BOICE, R., HUGHES, D., & COBB, C. J. Social dominance in gerbils and hamsters. Psychon. S c i . , 1969, 16(3), 127-128. BRENNAN,J. F. Running speed in the dominance tube. Psychon. S c i . , 1969, 14(3), 118. CORMAN,C. D., & BIONDO,J. Emotionality ratings and open-field behavior. Psychon.
Sci., 1969, 14(3), 122. 6.
7. 8. 9. 10. 11.
12. 13. 14. 15.
LINDZEY,G . , MANOSEVITZ,M., & WINSTON,H. Social dominance in the mouse. Psychon. Sci., 1966, 5, 451-452. MORRISON,B. J . Effect of size of rearing group on emotionality: Possible confounding with cage size. Psychol. Rep., 1968, 22, 1071-1072. NAGEY,H . , & HOLM,A. Open-field behavior of C57B16J mice; Effect of illumination, age, and number of test days. Psychon. Sci., 1970, 19(3) 143-145. RUSKIN,R. S.,& CORMAN,C. D. A multivariate study of competition in a free-operant situation. Psychon. S c i . , 1971, 23, 251-252. .The effects of varying levels of deprivation on the stability of dominancesubmission hierarchies. Psychon. S c i . , 1971, 23, 361-363. . A method for the study of competition in a free-operant situation. 1. of Psychol., 1972, 81, 315-319. RUSKIN,R. S., THORNTON, W., & CORMAN,C. D. The relationship among dominance hierarchies determined in three competitive situations. Eastern Psychological Association, New York, New York, April, 1971. . Evidence for the situational specificity of dominance-submission. 1. Gen. Psychol., 1973, 88, 205-210. SINCH,D., & MAKI,W. S. Effects of post-weaning rearing conditions on emotionality and social-seeking behavior in the rat. Psychon. S c i . , 1968, 13(3), 163-164. WARD, I. L., & GERALL,A. A. Dominance behavior in socially isolated rats. Psychon. S c i . , 1968, 13(1), 39-40.
Department of Psychology Georgetown University Washington, D . C . 20057
THE RELATIONSHIP BETWEEN EMOTIONALITY AND DOMINANCE IN T H E HOODED RAT* Department of Psychology, Georgetown University
ROBERTs. RUSKIN,GREGORYG . DAVIS,AND ALEX DEPERALTA,JR. SUMMARY Hooded rodents were tested in an emotionality condition and two competitive “dominance” conditions. It was found that stable rankings of subjects within the test groups could be established for each of the three conditions. Significant negative correlations were also found between a subject’s “emotionality” ranking in a group and his ranking in the group in relation to either condition of competitive dominance, while a significant positive correlation was found between a subject’s ranking in both of the competitive dominance conditions. These data are taken as evidence for a debilitating effect of high emotionality on one’s success in competition.
INTRODUCTION Past research has noted studies involving either dominance or emotion hierarchies (lo), none has attempted to study the relationship, if any, between the two. Our goal is to determine the relationship between two types of competitive dominance and emotionality. A.
1. Emotion Prior research on emotionality in rodents has provided us with wellestablished measures. The procedures and methods for determining measures of emotion were provided in two studies: Corman and Biondo ( 5 ) and Singh and Maki (14). These studies have provided evidence that different emotions can be the result of pretesting factors. Field testing for emotionality is accomplished by employing standard measures in the open field, such as the number of squares traversed, latency in the starting squares, defecation rate, etc. Emotionality in rats has been found to be largely a function
* Received in the Editorial Office, Provincetown, Massachusetts, on February 7, 1974. Copyright, 1975, by The Journal Press. 53
54
JOURNAL OF GENERAL PSYCHOLOGY
of early enironmental variables, such as early handling and isolation (2, 15). Threfore, emotionality ratings can be viewed as having been the result of factors preceding experimentation. Different aspects of emotionality have been studied to determine its etiology and to seek relationships to other forms of behavior (14). In this study we attempted to correlate it to dominance and have neglected its etiology on the assumption that it does exist and hence can be adequately measured. 2 . Dominance Dominance studies have been abundant, centering upon various aspects of the concept in order to compile a complete repertoire of the behaviors and other factors which may influence it. Procedures and measures have been secured mainly from studies by Boice et al. (3, Ruskin and Corman (9) and Ward and Gerall (15). Measures for our study included latency, nose-poke, and pellet competition. These measures have been proven highly reliable in prior research (12). Studies have found that different tests of dominance may be largely determined by the specific competitive situation. For example, dominance in one set of measures, such as between the competitive running tube and single food pellet competition, have shown a negative correlation (6), while speed in the running tube has shown a positive correlation (4). In this study, therefore, we have limited our competitive measures to only food-related competition, to eliminate the effect of situational factors.
B.
METHOD
1. Subjects
The subjects were 42 black-white hooded male rats, 30 days of age at the beginning of testing. All subjects were randomly divided into seven groups of six subjects each and were handled for 14 consecutive days by the experimenters in order to insure their docility and to provide optimal and constant treatment (1, 8). Immediately upon weaning, each subject was placed into a separate cage of equal size (7) constructed of metal which allowed free access to water at all times. During Phase I, emotionality testing, subjects were given an unlimited supply of food; during Phase 11, competitive testing, subjects were placed on 24-hour food deprivation but allowed free access to water at all times. 2. Apparatus An open field apparatus constructed of a masonite floor measuring 45 X 45 inches and wooden walls 24 inches high was employed during testing for
ROBERT S. RUSKIN ET AL.
55
emotionality. The floor area was divided into 25 equal parts identified by 9 x 9 inch black tiles. In addition, three zones were defined as (a) outside or peripheral squares, (b) center squares (all squares except the peripheral and white squares), and (c) the white square which was the actual center of the open field. The walls and starting box were painted gray. The open field apparatus was situated to allow direct viewing through a one-way mirror and concurrent videotaping. A Sony videotape apparatus, television monitor, and camera were used during testing. The television monitor allowed the experimenters to score all relevant behaviors accurately, utilizing replays if necessary. A “nose-poke” apparatus was included during Phase 11. The nose-poke was 12 x 12 inches, with an access hole 1% inches in diameter to Noyes food pellets which were delivered through a metal tube and onto a magazine tray behind the opening. The size and nature of the hole limited the feeding to only one rat at any given time. 3 . Procedure Phase Z: Phase I consisted of obtaining emotionality measures including activity, latency, and locale measures. Latency was defined as the time the subject spent before leaving the starting square. Activity was defined as the total number of squares traversed during each three-minute trial. Squares were counted as being traversed when the subject actually touched an adjacent square with both front paws. Locale measures were defined as the time subjects spent in each of the three zones: the outer squares, the “center” black squares, and the white square in the exact center of the apparatus. Each subject was tested during three-minute trials once a day for 20 consecutive days. The subject-testing sequence was randomized to control for order-effects. Testing was conducted during the same time period each day so that consistency with the subject’s circadian rhythm would not be interrupted. b. Phase ZZ: All subjects were placed on 24-hour deprivation schedules and tested with each of its “group members” assigned in Phase I. This phase included two different competitive situations. One was a dominance test employing single-pellet competition. Two rats were placed in the open field apparatus and competed for a single large food pellet which was originally placed on the white center square. The “winner” of each trial was operationally defined as that subject (of each competing pair) which had the highest latency in possession of the food pellet. All subjects were concurrently tested in a nose-poke apparatus, and the a.
56
JOURNAL OF GENERAL PSYCHOLOGY
complete procedure is described in detail in Ruskin and Corman (11). Round-robin pairings in the nose-poke or “limited access” condition were randomized with single pellet testing in order to eliminate any sequential effects of testing. Two standardized nose-poke measures-number of nose-poke responses per competitor and the total time in nose-poke opening-were recorded, and winners were determined on the basis of those animals scoring highest in both measures. Before testing in the nose-poke, each subject was allowed to individually “overlearn” nose-poke responding. After each daily experimental session, all subjects were given access to food ad lib for 60 minutes. Testing in both conditions was completely randomized with respect to both the competition situation employed and the pairs of subjects competing in each trial. Testing continued each day until all subjects had been paired with all other members of its group in both competitive situations.
C. RESULTS AND DISCUSSION Subjects in each group were ranked daily from highest (most emotional) to lowest (least emotional) on the basis of the cumulative scores in each of the three measures of emotionality. Animals ranking highest in emotionality were assigned a rank of “1,” next highest animal a “2,” and so on through number “6” in each group. Coefficients of concordance were computed over the 20 test days for the emotionality condition and for both competitive situations. These results are presented in Table 1. It is interesting to note that six of the seven groups show significant coefficients in the emotionality (Phase I) condition, six of the seven groups show significant coefficients in the single pellet “dominance” condition of TABLE 1 SIGNIFICANCE POINTS(S) FOR THE COEFFICIENT ON CONCORDANCE (W) I N THE EMOTIONALITY, LIMITEDACCESSDOMINANCE AND SINGLE-PELLET DOMINANCE CONDITIONS GrOUDS
Emotionality
Limited Access Dominance
Single-Pellet Dominance
1 2 3 4 5 6
897.1 774.6 634.3 940.0 873.6 826.2 893.4
780.3 813.4 829.6 796.5 831.4 908.7 872.8
793.2 801.4 921.6 880.7 835.5 751.0 789.9
7
Note: Number of subjects per group = 6; Number of days tested = 20; S
=
764.4, p
< .05.
57
ROBERT S. RUSKIN ET AL.
Phase II, and all seven groups show significant coefficients in the limited access nose-poke condition. The high degree of concordance in the two “dominance” conditions supports previous research (13). The degree of concordance in the emotionality ranking over the days gives evidence for a highly stable phenomenon. This evidence is augmented by the fact that the absolute scores on each of the emotionality measures when reviewed decreased over trials with every subject, but subject’s emotionality rankings relative to other members in the group stayed virtually the same. The number of “wins” of each subject over the entire 20 day test period was then computed for each of the emotionality and two competitive conditions. Each subject could receive a maximum total of 100 (five possible wins over all other group members daily times 20 test days per test condition) for the emotionality, single pellet competitive, or limited access competitive conditions. The minimum total number of wins was zero for each condition. A Pearson product-moment correlation was then determined between the number of wins in each test condition, and these results appear in Table 2. The results indicate that a subject’s emotionality correlates significantly with both “dominance” conditions. Moreover these data show that the higher the emotionality of a subject, the lower the subject’s ranking on either test of competitive dominance. It is interesting to note that this relationship is slightly more apparent between the single pellet competitive condition and the emotionality condition. One possible explanation for this slight although noticeable difference may simply lie in the fact that single pellet competition requires not only aggressive behavior from the competition but also a variety of different and rapidly developed responses, such as running with the pellet, sparring, posturing, etc. Animals who
PEARSON
TABLE 2 PRODUCT-MOMENT CORRELATIONS (r) BETWEENEMOTIONALITY AND SINGLEPELLETAND LIMITEDACCESSCOMPETITIVE DOMINANCE
Condition Emotionality Single-Pellet Dominance Limited Access Dominance
Emotionality 1.000
Single-Pellet Dominance
Limited Access Dominance
-.424 1.000
-.376 ,530
Note: df = 40; p < .01, r = ,393; p < .05, r = ,304.
1.OOO
58
JOURNAL OF GENERAL PSYCHOLOGY
exhibit rigid posturings and general lack of activity in the open-field apparatus because of extreme emotionality would not therefore be likely to exhibit the behaviors necessary for success in single-pellet competition. The data show a significant positive relationship between those subjects who rank highly in competition for single-pellets of food and those subjects who rank highly in limited access competition. These results lend support to similar previous findings (13) in which these competitive conditions were compared. These data indicate that rodents with high levels of emotionality tend to do poorly in the competitive conditions tested. The extent to which these results can be generalized to other competitive situations or test apparatus should certainly be the subject of future research in this area. REFERENCES 1. 2.
3. 4.
5.
BECKER,G. Dominance-subordination polarity in early-handled and nonhandled rats. Psychon. S c i . , 1968, 11(3), 115-116. BECKER,G., & GERARD,E. Early-handling and social-rearing effects on dominancesubordination behavior in the adult rat. Psychon. Sci., 1969, l y l ) , 27-28. BOICE, R., HUGHES, D., & COBB, C. J. Social dominance in gerbils and hamsters. Psychon. S c i . , 1969, 16(3), 127-128. BRENNAN,J. F. Running speed in the dominance tube. Psychon. S c i . , 1969, 14(3), 118. CORMAN,C. D., & BIONDO,J. Emotionality ratings and open-field behavior. Psychon.
Sci., 1969, 14(3), 122. 6.
7. 8. 9. 10. 11.
12. 13. 14. 15.
LINDZEY,G . , MANOSEVITZ,M., & WINSTON,H. Social dominance in the mouse. Psychon. Sci., 1966, 5, 451-452. MORRISON,B. J . Effect of size of rearing group on emotionality: Possible confounding with cage size. Psychol. Rep., 1968, 22, 1071-1072. NAGEY,H . , & HOLM,A. Open-field behavior of C57B16J mice; Effect of illumination, age, and number of test days. Psychon. Sci., 1970, 19(3) 143-145. RUSKIN,R. S.,& CORMAN,C. D. A multivariate study of competition in a free-operant situation. Psychon. S c i . , 1971, 23, 251-252. .The effects of varying levels of deprivation on the stability of dominancesubmission hierarchies. Psychon. S c i . , 1971, 23, 361-363. . A method for the study of competition in a free-operant situation. 1. of Psychol., 1972, 81, 315-319. RUSKIN,R. S., THORNTON, W., & CORMAN,C. D. The relationship among dominance hierarchies determined in three competitive situations. Eastern Psychological Association, New York, New York, April, 1971. . Evidence for the situational specificity of dominance-submission. 1. Gen. Psychol., 1973, 88, 205-210. SINCH,D., & MAKI,W. S. Effects of post-weaning rearing conditions on emotionality and social-seeking behavior in the rat. Psychon. S c i . , 1968, 13(3), 163-164. WARD, I. L., & GERALL,A. A. Dominance behavior in socially isolated rats. Psychon. S c i . , 1968, 13(1), 39-40.
Department of Psychology Georgetown University Washington, D . C . 20057
