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Escape and avoidance learning as a function of emotionality level in the wyoming ground squirrel
BRIEF COMMUNICATIONS ESCAPE AND AVOIDANCE LEARNING AS A FUNCTION OF EMOTIONALITY LEVEL IN THE WYOMING GROUND SQUIRREL Citellus richardsonii elegans ROLLIN H . DENNISTON, 11 University of Wyoming
The object of this study is to determine whether a significant difference might exist in the learning of escape and avoidance from electrical shock between thoroughly cage-conditioned and freshly caught Wyoming ground squirrels . The problem suggested itself following the reading of Spence's (1956) Behaviour theory and conditioning, Miller's (1948) Fear as an acquirable drive, and certain observations of wild animal behaviour in both field (1959-1956) and laboratory (1057 a & b) . , The concensus seems to be that anxious subjects (human) condition faster and to a significantly higher level than less anxious subjects . Rather different hypothetical constructs have been utilised in attempts to throw light on the situation, notably by Spence & Taylor (1953), Hilgard, et al (1951) and Miller (op . cit .) . Having at hand a group of newlycaught and apparently "emotional" ground squirrels and a standard stock of well cageconditioned squirrels of the same species, we felt that data obtainable from them might throw some further light on the general problem of learning an instrumental response by emotional and less emotional subjects .
the type cited above . This group was labelled "Old" . Animals of both groups were mature and comparable in weights . Although the author had had fifteen years' experience working with ground squirrels in the laboratory and felt that he knew that newly caught subjects were significantly more "emotional" than those adequately cage-conditioned, he had never run actual emotionality scores until undertaking the present series of experiments . Subjects were observed in their home cages in a series of five-minute check periods on successive days . A clean paper was introduced into the dropping tray at the beginning of each observation for fecal pellet counts and urination determination . If a subject vocalised in three of the five minutes, a positive score was recorded for this criterion . The conditioning apparatus was a standard shocking grid 50 cm . x 30 cm ., either half of which could be activated by an induced current to serve as the unconditioned stimulus (US) . The conditioned stimulus (CS) was a 60-cycle buzzer . The grid covered the floor of a cage 30 cm . high, the two halves being separated by a fence 15 cm. high . The subjects were visible to E through a suitably illuminated one-way vision mirror . All subjects were allowed to explore the conditioning apparatus for ten minutes on each of three days with buzzer and shock off, and were then given three sessions each of 3S . Sixteen subjects which persisted in responding to the CS by jumping the fence were eliminated from the experiment. Two animals either died or became seriously ill and were eliminated for that reason . Eighteen subjects were now exposed to the following regimen : two minutes adjustment to apparatus, 30 seconds CS, 30 seconds US . If the subject did not cross, he was placed on the other side, and all had the procedure repeated in the opposite direction . Fourteen daily pairs of trials were made for each S . Latencies of response to CS, US, and other incidental notes were made by E.
Method Thirty-six adult male Wyoming ground squirrels were the subjects in these experiments . They were captured by the author from the same area of approximately a square mile near Laramie, Wyoming. Members of one group were captured no more than ten days before the beginning of the experimental work . This group was labelled "New" . Its members showed many signs of "wildness" or "anxiety", such as high defecatory, urinary, and vocalisation rates and frequency, both in and out of the immediate presence of the observer . These also reacted much more violently to handling than did the cageconditioned group . Members of the second group had been confined to the laboratory colony for at least a year . These animals were much lower in anxiety-associated responses of 241
242
ANIMAL BEHAVIOUR,
Results As far as defaecation, urination and vocalisation may be accepted as criteria of "emotionality", the newly caught were significantly more emotional than the cage-conditioned subjects. Table I. "Emotionality" Scores (per animal-trial)
Defecation
N
Urination % Vocalisation
VII, 3-4
Table It. Escape Response i %
Old
127/222
57 . 20
New
156/246
Difference
29
i
S.E. A
Old 19
5 . 35±2 . 49
17 . 54
50 . 9
New 17
10 . 60±2 . 92
37 . 25
84'3
t
9 . 47
2 . 23
3 . 55
p
< •001
< .05
< •0 01
1 . 38
63 . 41
5.4
0 . 48
6 . 21
5.7
I
P
1 28
<1 .0
< -001
Table III . Avoidance Response
%
Seconds latency
Old
31/222
13 . 96
15'6
New
5/246
2 . 03
16 . 0
Difference P
26
11-93-L2-46
'4
< .002
such a response . There was no significant difference in avoidance response latency between the two groups.
Discussion Although the new group of "anxious" subjects learned to respond to the shock with much shorter latency than the old, cage-conditioned group, the RESPONSE new group never learned to avoid the shock by responding to the warning buzzer. The old, less "anxious" group learned this avoidance response to CS quite satisfact. NEW orily . This better learning by 11, "less emotional" subjects is, superficially at least, conESCAPE trary to a large body of data 0 which shows "high drive" ~\ t CAGE subjects to be superior learnP CONDITIONED ers . Many of these data are summarised in Spence (1956, op . cit.) . However, the same .e `r AVOIDANCE volume contains several suggestions which may help to explain our findings . The NEW curve presented by Fig. 7 (p . F la IV V VI VI1 1 Ix x xl wl xll XIV 173) demonstrates a lessened rate of response under higher Fig . 1 . Average escape and avoidance frequencies, a a a a I 1
TRIALS
1 I1'l 1
4 . 52
Incidence Response to US Although not .all subjects escaped from shock on even the last trial (78 per cent .-old and 67 per cent . new, see Fig . 1), all had shown escape response to US during the series . There was no significant difference between old and new groups in incidence of escape response . There was a significant difference in escape latencies. The new group responded much faster to US . The new group showed a significantly lower level of learning avoidance response . On the last trial 36 per cent . of the old group responded to the CS, whereas none of the new group gave
Seconds latency
Incidence
II
a 1 a a a
DENNISTON : ESCAPE & AVOIDANCE LEARNING IN THE WYOMING GROUND SQUIRREL
levels of aversive stimulation . The material included in Section 7, and especially the footnote on page 222 suggests that increased oscillation between competing responses may be expected to occur at high drive levels . One possible reason for the difficulty in learning the avoidance response apparent in our "anxious" group was that members of this group tended to "freeze" into immobility, as a response to novel environmental change . The response of freezing is obviously incompatible with avoidance response. Assuming that both the CS, or buzzer and the US, or shock were aversive, the US must further be assumed to be of such a nature, quantitatively or qualitatively, that the response tendency to it was sufficiently strong to overcome the incompatible SUR of freezing . In Hullian (1952) symbolism SUR signifies an unlearned stimulus-response connection, and SER, a present reaction potential . So for the "anxious" group : S ER (Escape)> SUR (Freezing)> SER (Avoidance) . But for the "less anxious" group : SE R (Escape)> SER (Avoidance)> 5UR(Freezing) . Although it may be true that the response tendency of an organism is in part the result of total drive level, and presumably there was a greater total drive in the anxious than the nonanxious group, the only measure we have of drive is response, and if the unlearned response tendency is incompatible with the learned response, apparently paradoxical differences in response between anxious and non-anxious groups may result . We believe it to be an oversimplification to interpret these data as overmotivation interfering with the learning of an expectancy. A superficial interpretation of these results might stop with the assumption that the newly caught group failed to learn avoidance because of giving the incompatible unlearned response of freezing . A more careful examination of the situation makes it apparent that the reason the new animals froze was because they were more anxious than the cage-conditioned subjects . In animal, and possibly in human subjects, under high anxiety there is at least one
2 43
other response than avoidance possible to noxious stimuli, namely freezing . Unless this possibility is recognized chaos may result in attempting to interpret data from shock conditioning . Summary An attempt was made to teach recently caught "anxious" wild rodents and thoroughly cageconditioned subjects of the same species an avoidance response to a buzzer preceding shock . The less anxious cage-conditioned group learned the response more quickly and thoroughly than the more anxious group . Possibly this difference was, in part, due to the fact that newly caught animals tend to give the incompatible response of freezing to aversive but not actively noxious stimuli . Acknowledgments 1 . This work was supported by National Institute of Mental Health Grant No . 969. 2. The author is indebted to Mrs . Mellee Luton-Fish for many of the observational data here reported . REFERENCES Denniston, R . H. (1949) . Certain aspects of the development and behaviour of the Wyoming moose . Anat. Rec., 105, 137 . Denniston, R . H . (1956) . The behaviour, ecology, and population dynamics of the Wyoming or Rocky Mountain moose, Alces alces shirasi . Zoologica, 41, 105-118. Denniston, R . H. (1957a) . Notes on breeding and size of young in the Richardson ground squirrel . J. Mammal ., 38,414-416. Denniston, R . H . (1957b) . Sexual behaviour and physiology cycle in an annual breeding wild rodent . Anat. Rec ., 128, 539 . Hilgard, E . R ., Jones, L . W., & Kaplan, S. J. (1951) . Conditioned discrimination as related to anxiety . J. exp . Psychol., 42, 94-100 . Hull, C . L . (1952). A behaviour system . New Haven : Yale University Press . Miller, N. E . (1948) . Studies of fear as an acquirable drive . J. exp . Psychol., 38, 89-101 . Spence, K . W. (1956) . Behaviour theory and conditioning . New Haven : Yale University Press . Spence, D . W . & Taylor, J . A . (1953) . The relation of conditioned response strength to anxiety in normal, neurotic and psychotic subjects . J. exp . Psychol ., 45, 265-272. Accepted for publication 20th March, 1959 .
The object of this study is to determine whether a significant difference might exist in the learning of escape and avoidance from electrical shock between thoroughly cage-conditioned and freshly caught Wyoming ground squirrels . The problem suggested itself following the reading of Spence's (1956) Behaviour theory and conditioning, Miller's (1948) Fear as an acquirable drive, and certain observations of wild animal behaviour in both field (1959-1956) and laboratory (1057 a & b) . , The concensus seems to be that anxious subjects (human) condition faster and to a significantly higher level than less anxious subjects . Rather different hypothetical constructs have been utilised in attempts to throw light on the situation, notably by Spence & Taylor (1953), Hilgard, et al (1951) and Miller (op . cit .) . Having at hand a group of newlycaught and apparently "emotional" ground squirrels and a standard stock of well cageconditioned squirrels of the same species, we felt that data obtainable from them might throw some further light on the general problem of learning an instrumental response by emotional and less emotional subjects .
the type cited above . This group was labelled "Old" . Animals of both groups were mature and comparable in weights . Although the author had had fifteen years' experience working with ground squirrels in the laboratory and felt that he knew that newly caught subjects were significantly more "emotional" than those adequately cage-conditioned, he had never run actual emotionality scores until undertaking the present series of experiments . Subjects were observed in their home cages in a series of five-minute check periods on successive days . A clean paper was introduced into the dropping tray at the beginning of each observation for fecal pellet counts and urination determination . If a subject vocalised in three of the five minutes, a positive score was recorded for this criterion . The conditioning apparatus was a standard shocking grid 50 cm . x 30 cm ., either half of which could be activated by an induced current to serve as the unconditioned stimulus (US) . The conditioned stimulus (CS) was a 60-cycle buzzer . The grid covered the floor of a cage 30 cm . high, the two halves being separated by a fence 15 cm. high . The subjects were visible to E through a suitably illuminated one-way vision mirror . All subjects were allowed to explore the conditioning apparatus for ten minutes on each of three days with buzzer and shock off, and were then given three sessions each of 3S . Sixteen subjects which persisted in responding to the CS by jumping the fence were eliminated from the experiment. Two animals either died or became seriously ill and were eliminated for that reason . Eighteen subjects were now exposed to the following regimen : two minutes adjustment to apparatus, 30 seconds CS, 30 seconds US . If the subject did not cross, he was placed on the other side, and all had the procedure repeated in the opposite direction . Fourteen daily pairs of trials were made for each S . Latencies of response to CS, US, and other incidental notes were made by E.
Method Thirty-six adult male Wyoming ground squirrels were the subjects in these experiments . They were captured by the author from the same area of approximately a square mile near Laramie, Wyoming. Members of one group were captured no more than ten days before the beginning of the experimental work . This group was labelled "New" . Its members showed many signs of "wildness" or "anxiety", such as high defecatory, urinary, and vocalisation rates and frequency, both in and out of the immediate presence of the observer . These also reacted much more violently to handling than did the cageconditioned group . Members of the second group had been confined to the laboratory colony for at least a year . These animals were much lower in anxiety-associated responses of 241
242
ANIMAL BEHAVIOUR,
Results As far as defaecation, urination and vocalisation may be accepted as criteria of "emotionality", the newly caught were significantly more emotional than the cage-conditioned subjects. Table I. "Emotionality" Scores (per animal-trial)
Defecation
N
Urination % Vocalisation
VII, 3-4
Table It. Escape Response i %
Old
127/222
57 . 20
New
156/246
Difference
29
i
S.E. A
Old 19
5 . 35±2 . 49
17 . 54
50 . 9
New 17
10 . 60±2 . 92
37 . 25
84'3
t
9 . 47
2 . 23
3 . 55
p
< •001
< .05
< •0 01
1 . 38
63 . 41
5.4
0 . 48
6 . 21
5.7
I
P
1 28
<1 .0
< -001
Table III . Avoidance Response
%
Seconds latency
Old
31/222
13 . 96
15'6
New
5/246
2 . 03
16 . 0
Difference P
26
11-93-L2-46
'4
< .002
such a response . There was no significant difference in avoidance response latency between the two groups.
Discussion Although the new group of "anxious" subjects learned to respond to the shock with much shorter latency than the old, cage-conditioned group, the RESPONSE new group never learned to avoid the shock by responding to the warning buzzer. The old, less "anxious" group learned this avoidance response to CS quite satisfact. NEW orily . This better learning by 11, "less emotional" subjects is, superficially at least, conESCAPE trary to a large body of data 0 which shows "high drive" ~\ t CAGE subjects to be superior learnP CONDITIONED ers . Many of these data are summarised in Spence (1956, op . cit.) . However, the same .e `r AVOIDANCE volume contains several suggestions which may help to explain our findings . The NEW curve presented by Fig. 7 (p . F la IV V VI VI1 1 Ix x xl wl xll XIV 173) demonstrates a lessened rate of response under higher Fig . 1 . Average escape and avoidance frequencies, a a a a I 1
TRIALS
1 I1'l 1
4 . 52
Incidence Response to US Although not .all subjects escaped from shock on even the last trial (78 per cent .-old and 67 per cent . new, see Fig . 1), all had shown escape response to US during the series . There was no significant difference between old and new groups in incidence of escape response . There was a significant difference in escape latencies. The new group responded much faster to US . The new group showed a significantly lower level of learning avoidance response . On the last trial 36 per cent . of the old group responded to the CS, whereas none of the new group gave
Seconds latency
Incidence
II
a 1 a a a
DENNISTON : ESCAPE & AVOIDANCE LEARNING IN THE WYOMING GROUND SQUIRREL
levels of aversive stimulation . The material included in Section 7, and especially the footnote on page 222 suggests that increased oscillation between competing responses may be expected to occur at high drive levels . One possible reason for the difficulty in learning the avoidance response apparent in our "anxious" group was that members of this group tended to "freeze" into immobility, as a response to novel environmental change . The response of freezing is obviously incompatible with avoidance response. Assuming that both the CS, or buzzer and the US, or shock were aversive, the US must further be assumed to be of such a nature, quantitatively or qualitatively, that the response tendency to it was sufficiently strong to overcome the incompatible SUR of freezing . In Hullian (1952) symbolism SUR signifies an unlearned stimulus-response connection, and SER, a present reaction potential . So for the "anxious" group : S ER (Escape)> SUR (Freezing)> SER (Avoidance) . But for the "less anxious" group : SE R (Escape)> SER (Avoidance)> 5UR(Freezing) . Although it may be true that the response tendency of an organism is in part the result of total drive level, and presumably there was a greater total drive in the anxious than the nonanxious group, the only measure we have of drive is response, and if the unlearned response tendency is incompatible with the learned response, apparently paradoxical differences in response between anxious and non-anxious groups may result . We believe it to be an oversimplification to interpret these data as overmotivation interfering with the learning of an expectancy. A superficial interpretation of these results might stop with the assumption that the newly caught group failed to learn avoidance because of giving the incompatible unlearned response of freezing . A more careful examination of the situation makes it apparent that the reason the new animals froze was because they were more anxious than the cage-conditioned subjects . In animal, and possibly in human subjects, under high anxiety there is at least one
2 43
other response than avoidance possible to noxious stimuli, namely freezing . Unless this possibility is recognized chaos may result in attempting to interpret data from shock conditioning . Summary An attempt was made to teach recently caught "anxious" wild rodents and thoroughly cageconditioned subjects of the same species an avoidance response to a buzzer preceding shock . The less anxious cage-conditioned group learned the response more quickly and thoroughly than the more anxious group . Possibly this difference was, in part, due to the fact that newly caught animals tend to give the incompatible response of freezing to aversive but not actively noxious stimuli . Acknowledgments 1 . This work was supported by National Institute of Mental Health Grant No . 969. 2. The author is indebted to Mrs . Mellee Luton-Fish for many of the observational data here reported . REFERENCES Denniston, R . H. (1949) . Certain aspects of the development and behaviour of the Wyoming moose . Anat. Rec., 105, 137 . Denniston, R . H . (1956) . The behaviour, ecology, and population dynamics of the Wyoming or Rocky Mountain moose, Alces alces shirasi . Zoologica, 41, 105-118. Denniston, R . H. (1957a) . Notes on breeding and size of young in the Richardson ground squirrel . J. Mammal ., 38,414-416. Denniston, R . H . (1957b) . Sexual behaviour and physiology cycle in an annual breeding wild rodent . Anat. Rec ., 128, 539 . Hilgard, E . R ., Jones, L . W., & Kaplan, S. J. (1951) . Conditioned discrimination as related to anxiety . J. exp . Psychol., 42, 94-100 . Hull, C . L . (1952). A behaviour system . New Haven : Yale University Press . Miller, N. E . (1948) . Studies of fear as an acquirable drive . J. exp . Psychol., 38, 89-101 . Spence, K . W. (1956) . Behaviour theory and conditioning . New Haven : Yale University Press . Spence, D . W . & Taylor, J . A . (1953) . The relation of conditioned response strength to anxiety in normal, neurotic and psychotic subjects . J. exp . Psychol ., 45, 265-272. Accepted for publication 20th March, 1959 .