D. L. Hammell 2 , D. D. Kratzer and W. J. Bramble University o f Kentucky, Lexington 40506 Sr~mmary An experiment involving 120 pigs, with four pigs randomly selected from each of 30 litters, was conducted to determine the relationship between avoidance learning and water-maze learning, and to determine which pattern or patterns in a water-maze would reflect maximum differences in learning ability. Decreases in total errors and total latency indicated learning occurred on the non-alternating patterns. Significant correlations were observed among avoidance learning criteria and among water-maze learning criteria, but no significant correlations were observed between avoidance learning and maze learning criteria. Because of this correlation pattern two principal components were identified; one principal component was identified as a measure of avoidance learning ability and a second principal component was identified as a measure of water-maze learning ability. Introduction The ability of pigs to perceive environmental cues and change their behavior to adapt to stressful situations surely has economic merit. Studying the learning ability of pigs will give the animal scientist insight into the degree of behavioral adaptability pigs have for complex environmental situations. Reliable measures of learning for pigs are also needed where pigs are used as models for making inferences about factors that affect human lezrning ability. For example, Karas et al. Department of Animal Sciences. Kentucky Agricultural Experiment Station Journal Paper No. 74-5-26. 2 Present address: University of Florida, Agricultt~_ral Research Center, Live Oak 32060.
(1962), Willham et al. (1964) and Kratzer (1965) used pigs as a model for studying the effects of x-irradation on learning ability of humans. Barnes et al. (1970) and Hammel (1973) used pigs as a model for studying the effects of protein deficiency on learning ability of humans. Several scientists have found factors that affect learning abilities of pigs. Wickert and Barr (1966) reported significant breed and sex differences in the ability of pigs to perform in a T-maze. Kratzer (1969a) also reported a significant difference in avoidance learning ability of Hampshire and Duroc breeds of pigs. Research by Baldwin and Ingram (1967) indicates that pigs may be conditioned to press a switch with their snouts and obtain heat from an infra-red lamp when "housed in a cold environment. The use of certain learning procedures may aid researchers in determining which pigs would most effectively control their environment. Kratzer (1971) suggests learning ability should be measured on several tasks to avoid inferences about learning that may apply only to a specific task. The number of techniques for measuring learning in pigs is limited. Karas et al. (1962) presented results with a shock-avoidance apparatus in which pigs were conditioned to jump a hurdle in response to a buzzer. Wickert and Barr (1966) reported on the performance of pigs in a T-maze. Pigs were isolated from their dams and then allowed to go through the maze. Time spent in the maze was the response criterion. The isolation of the pig from its dam and littermates was the driving stimulus. Additional quantitative procedure for measuring learning in pigs are needed. This research was done to study water-maze learning as a technique for measuring learning
573 JOURNAL OF ANIMAL SCIENCE, vol. 4 0 , n o . 3, 19"/5
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AVOIDANCE AND MAZE LEARNING IN PIGS 1
574
HAMMELL, KRATZER AND BRAMBLE
Experimental Procedure One hundred-twenty Hampshire x Yorkshire crossbred pigs, four pigs randomly selected from each of 30 litters, were tested for learning ability at 21 days of age in a Warner-type shuttle box adapted for swine. It consisted of a 1.83 x .61 x .61 m plywood box divided in the center by a 12.7 cm wooden barrier. The grid floor was constructed of 1.27 cm square, chrome plated bars spaced 1.27 cm apart. The floor was connected to a control box which activated the conditioned and unconditioned stimuli. The conditioned stimulus was a telephone buzzer attached to the shuttle box. The unconditioned stimulus was a sub-tetanizing level of shock delivered to the feet of the pigs via the grid floor. The response to be conditioned was movement over the central barrier. For a detailed explanation of the apparatus see Willham et al. (1964). The procedure for testing a 21-day-old pig in the shuttle box was as follows: (1) wet the pig's feet, (2) place the pig in the shuttle box on the right side of the central barrier, (3) activate the grid-half occupied by the pig, (4) start the trial with the sound of a buzzer for 6 sec, (5) if the conditioned response has not occurred, apply shock until the pig has cleared the central barrier with its front feet or a limit of 99.9 sec has elapsed. The pig could receive shock for a maximum of 93.9 sec, (6) 12-see inter-trial interval, (7) repeat steps 3 through 6 five times on the first 2 test days and 10 times on the third test day. Steps 4 through 6 were controlled automatically by instrumentation. The criteria used as measures of avoidance learning were adopted from Kratzer (1965) and were number of avoidances and escape latencies on the third day of testing. An avoidance was defined as the pig's jumping over the 12.7 cm central barrier in response to the 6.0-sec warning buzzer to avoid foot shock. Escape latency was defined as the time interval from unconditioned stimulus until response. The average escape latency was calculated because
the number of escapes, 10 minus the number of avoidances, could vary from pig to pig. Every pig in this experiment had at least one escape. Testing for avoidance learning ability was started when the pigs were 19 days of age. At 45 days of age pigs were tested in a three-choice-point water-maze. The maze was in a galvanized tank 9.14 m long, 2.44 m wide, and .61 m deep and filled with water. To prevent pigs from jumping out of the tank, galvanized sheet metal was placed around the tank creating a .61 m vertical extension. A diagram of the tank is presented in figure 1. The study was done in a randomized complete block design with litters as blocks and four maze patterns as treatments. One pig from each litter was randomly assigned to each of four maze patterns. Two alternating and two non-alternating patterns were chosen from the eight possible patterns. The alternating patterns of left-right-left and right-left-right are presented in figure 2. The non-alternating patterns of left-left-left and right-fight-right are pre-
iJ
9.2 Meters
w
1 v
2.4 Meters Figure 1. Diagram of Water-Maze
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in pigs and specifically to determine which pattern or patterns in a water-maze would reflect maximum differences in learning ability. In addition, the relationship among measures of avoidance learning and water-maze learning was studied.
AVOIDANCE OF MAZE LEARNING IN PIGS
--
|
I
I
to~J
iii
Results and Discussion
jo'
---:;/----
Left--Right-Left
Totals were obtained for the three trials of a given day. The data were analyzed using analysis of variance, correlation and principal component techniques. The computer programs, Statistical Analysis Systems (Barr and Goodnight, 1971) and Univariate and Multivariate Analysis of Variance and Covariance: A Fortran IV Program (Finn, 1968), were used in analyzing the data.
,
, ,
Right-Left-Right
Figure 2. Alternating Maze Patterns
sented in figure 3. Learning ability was defined as the pig's ability to maneuver through three choice-points evenly spaced throughout the tank. The procedure for testing water-maze learning ability of pigs as follows: (1) pigs were tested 3 successive days with three trials daily with a maximum trial length of 2 min; (2) on day 1, pigs were conditioned to go through the water-maze and not allowed to retrace. Either a left or right choice at any choice-point allowed escape; (3) on day 2, pigs were introduced to their assigned escape pattern described in figures 2 and 3; (4) day 3 was repetitious of day 2. The criteria selected to reflect learning in the water-maze were total errors, total latency. These criteria were recorded on both days 2 and 3 of testing. An error was defined as swimming through a choice-point in the water-maze which would not allow escape, and a correct response was defined as swimming through a choice-point which would allow escape. Latency was defined as the time interval from entry into the tank until exit from the tank and could not exceed 2 min for any trial.
The means of avoidance learning scores on day 3 and maze learning responses on days 2 and 3 are presented in tables 1 and 2, respectively. On day 2 of testing in the water-maze, significantly more errors and latency occurred on non-alternating than on alternating patterns. Differences encountered with these maze patterns are possibly due to the design of the maze. The alternating patterns shown in figure 3 show that the second correct choice-point and the third correct choice-point in the maze are in a straight line with the movement of the pig through the maze. With the non-alternating patterns the pigs
Left- Left- Left R ight- R ight- Right Figure 3. Non-Alternating Maze Patterns
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i
575
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HAIVIMELL, K R A T Z E R AND BRAMBLE
TABLE 1. MEANS OF AVOIDANCE LEARNING SCORES - DAY 3
Avoidances
2,53 3.00 2.70 2.60
79.4
Avg e s c a p e latency, sec
2,86 3.03 3.16 3.89 100.3
aCoefficient o f variation = s / ~ (100).
must change their direction of movement to prevent errors. Consequently, if a pig's desire is to take the most direct route through the maze it would make fewer errors and probably spend less time on alternating patterns than on non-alternating patterns. Comparisons among patterns on day 3 showed no significant differences for total errors and total latency. The performance of pigs on the non-alternating patterns was the same as the performance shown by pigs on the alternating patterns. Learning is reflected when an animal
TABLE 2. MEANS OF WATER-MAZERESPONSES ON DAYS 2 AND 3 Maze pattern Mazelearning
Maze learning
Total errors
8.03 5.40 4.83 7.30b49.9
Total corrects Totallatency
8.03 8.40 9.30c8.87 25.8 4.62 3.94 3.42 4.41d29.9 Day 3
Total errors
5.47 e 5.97 5.53 4.37 f 48.2 9,13 9.40 9.30 9.30 12.4 2.93 3.08 3.21 2.63 g38.9
Totallatency
Maze pattern
LLL LRL RLR RRR C.V. a Day 2
Total corrects
TABLE 3. COMPARISONSOF DAY 2 AND DAY 3 MEANS OF WATER-MAZERESPONSES
aCoefficient o f variation = s/x (100).
b8.03 + 7.30 significantly (P < .01) greater than 5.40 + 4.83. c 9 . 3 0 significantly (P < .10) greater than 8.40.
d4.62 + 4.41 significantly (P < .01) greater than 3.94 + 3.42.
e5.47 significantly (P < .10) greater than 4.37. f 5 . 9 7 + 5.53 significantly (P < .10) greater than 5.47 + 4.37. g3.08 + 3.21 significantly (P < 2 . 9 3 + 2.63.
,10) greater than
LLL LRL
RLR
RRR
4.83 9.30 3.42
7.30 8,87 4,41
Day 2 Total errors Total corrects Total latency
8.03 8.03 4.62
5.40 8,40 3,94 Day 3
Total errors
5,47a 5.97
5.53
4.37 b
Total corrects
9,13c 9.40d
9.30
9.30
Total latency
2,93 e 3.08 g
3.21
2.63f
a5.47 significantly (P < .01) less than 8.03, b4.37 significantly (P < .01) less than 7.30. c9.13 significantly (P < .05) more than 8.03. d9.40 significantly (P < .05) more than 8.40. e2.93 significantly (P < .01) less than 4,62, f2.63 significantly (P < .01) less than 4.41. g3.08 significantly (P < .01) less than 3.94,
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Maze pattern Avoidance learning LLL LRL RLR RRR C.V. a
changes its responses in an adaptive manner. Comparisons were made between responses of day 2 and day 3 in the water-maze to determine if learning had occurred. If learning occurred the total errors and latency should decrease and the total correct responses should increase from day 2 to day 3. Since differences among patterns were inconsistent from day 2 to day 3, the comparisons between days were done separately for each maze pattern. Changes in responses from day 2 to day 3 are shown in table 3. In general, learning occurred on the alternating patterns but not on the non-alternating patterns, with the exception that, even though an increase in total corrects was observed on the right-right-right pattern it was not statistically significant. With regard to changes in responses on the alternating patterns, pigs on the left-left-left pattern showed significant increase in total corrects and a significant decrease in total latency. But pigs on alternating patterns did not show a decrease in errors; therefore, alternating patterns are not recommended for measuring learning abilities. Presented in tables 4 and 5 are the correlations of avoidance learning responses on day 3 and water-maze scores on day 2 and 3, respectively. There were significant differences
577
AVOIDANCE OF MAZE LEARNING IN PIGS TABLE 4. C O R R E L A T I O N S AMONG MEASURES OF AVOIDANCE L E A R N I N G AND WATER-MAZE L E A R N I N G ON DAY 2. A D J U S T E D F O R LITTERS AND P A T T E R N .
Maze learning Total errors Total corrects
Avoidances
Maze learning
Escape
Total
latency
errors
-- .03
.10
.15
-- .06
-- .06
.02
--
Total corrects
--.45**
Total latency
.65** --.38**
**P < .01.
among litters (P < .05) for water-maze learning on day 3 and significant differences among maze patterns on day 2 (P < .05). Therefore, correlations were adjusted for differences in maze patterns and litters. The correlation (r = -.34) between avoidances and average escape latency was significantly different from zero (P < .01). Pigs that make more avoidances also make faster escapes from shock. No significant correlations were observed between avoidance learning criteria and maze learning criteria on day 2 or 3 of testing. This finding is in agreement with previous results for pigs by Hammell (1973). Robustelli et al. (1963)found no significant correlation in rats between avoidance learning and maze learning. Their explanation applies to the results of this experiment and to quote: "The lack of correlation between the performances in the two tests might be attributed both to the different m o t i v a t i o n . . , and sensory requirements of the two tasks." In this experiment avoidance learning required perception of an auditory cue to avoid punishment whereas water-maze learning required spatial discrimination to escape from water. Principal-components analyses were used to study the relationships within the intercorrelations of avoidance and maze learning variables. In brief, a principal-component analysis reduces a matrix of correlations by extracting new
TABLE 5. CORRELATIONSAMONG MEASURES OF AVOIDANCE LEARNING AND WATERMAZE LEARNING ON DAY 3, ADJUSTED FOR LITTER AND PATTERN Avoidance learning
Avoidance learning
Maze learning
Escape Total Total Avoidances
latency
errors corrects
Escape latency
--
.34**
Maze
learning: Total errors Total corrects Total latency **P~.01.
-- .10
.06
.08
-- .02
-- .02
-- .05
--
-- .06
.71"*
.02
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Avoidance learning
variables called principal components which are correlated with the original variables but independent of each other. The first principalcomponent accounts for maximal variance among the original variables. The second principal-component accounts for maximal residual variance from the first principal-component. The third accounts for the residual from the first and second component, and so forth. By examining the correlations between the original variables and the principal-components one decides which variables overlap and which variables are separate. For a through explanation of principal-components analysis, see Overall and Klett (1972). Table 6 shows two principal-components for day 2. The first component was identified with maze learning by its significant ( P < .01) correlations with total errors (.87), total corrects ( - .69) total latency (.85). The second component was identified with avoidance, learning by its significant (P < .01) correlations with avoidances ( - .84) and average escape latency (.76). Table 7 shows three significant principal-
578
HAMMELL, K R A T Z E R AND BRAMBLE TABLE 6. PRINCIPAL-COMPONENTCORRELATIONS OF LEARNING SCORES ON DAY 2 Principal-component
Criteria
1
3
4
5
-- .02
-- .84**
.33
.41
.05
.16
.76**
.56
.29
.07
.03 .26 .01 1.36 27.18
--.17 -- .50 -- .33 .80 16.07
.21 .46 .11 .52 10.44
-- .40 --.01 .40 .33 .33
66.91
82.98
93.42
100.00
Maze learning Total errors Total corrects Total latency Eigenvaluea % of total variance Cumulative % of variance
.87** -- .69** .85** 1.99 39.73 39.73
aEigenvalues greater than 1 indicate a significant principal component. * * C o r r e l a t i o n s s i g n i f i c a n t (P ~ . 0 1 ) f o r values ~ . 5 0 .
components for day 3. The first principal component was identified with maze learning from its significant (P ( . 0 1 ) correlations with total errors (.93) and total latency (.91). This component was a reflection of slower times for those pigs that made more errors. The second principal-component was identified as an avoidance learning component because it was significantly (P ( . 0 1 ) correlated with avoidances ( - .81) and average escape latency (.80). Total corrects was significantly ( P ( . 0 1 )
correlated with the third principal-component on day 3. This was unlike the results from day 2 because on day 3, total corrects had small nonsignificant correlations with total errors and total latency. Since total errors and total latency appears to be independent of total corrects and total corrects did not increase significantly from day 2 to day 3, total corrects should not be used as a measure of learning. Since measures o f maze learning and
TABLE 7. PRINCIPAL-COMPONENTCORRELATIONS OF LEARNING SCORES ON DAY 3 Principal-component Criteria Avoidance learning Avoidances Average escape latency Maze learning Total errors Total corrects Total latency Eigenvaluea % of total variance Cumulative % of variance
1
2
3
4
5
-- .14 .08
-- .81"* .80**
-- .06 -- .22
.56 .55
.93** -- .04 .91"*
-- .01 .15 -- .18
-- .03 .97** .09
.00 .15 .04
-- .37 --.04 .36
1.71 34.31
1.35 26.06
1.01 20.24
.65 13.00
.27 5.49
34.31
61.27
81.51
94.51
100.00
aEigenvalues greater than 1 indicate a significant principal component. * * C o r r e l a t i o n s s i g n i f i c a n t ( P ~ . 0 1 ) f o r values ~ . 5 0 .
-- .05 .03
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Avoidance learning Avoidances Average escape latency
2
A V O I D A N C E O F M A Z E L E A R N I N G IN PIGS
Literature Cited Baldwin, B. A. and D. L. Ingrain. 1967. Behavioral thermoregulation in pigs. Physiol. and Behav. 2:15. Barnes, R. H., A. U. Moore and G. W. Pond 1970. Behavioral abnormalities in young adult pigs caused by malnutrition in early life. J. Nutr. 100:149. Barr, A. J. and J. H. Goodnight, 1971. Statistical analysis system. North Carolina State University, Raleigh. Finn, J. D. 1968. Univariate and multivariate analysis of variance and covariance: a fortran IV program. State University of New York, Bufffalo.
HammeU, D. L. 1973. Part I. Effect of protein restriction on reproduction in gilts and performance and learning of their offspring. Ph.D. Thesis. University of Kentucky, Lexington. Karas, G. G., R. L. Willham and D. F. Cox. 1962. Avoidance learning in swine. Psychol. Rep. 11:51. Kratzer, D. D. 1965. Learning behavior in swine. Dissertation Abstr. 26:4927. Ph.D. Thesis. Iowa State University, Ames. Kratzer, D. D. 1969a. Effects of age on avoidance learning in pigs. J. Anim. Sci, 28:175. Kratzer, D. D. 1971. Learning in farm animals. J. Anim. Sci. 32:1268. Overall, J. E. and C. J. Klett. 1972. Applied multivariate analysis. McGraw-HiU Book Co., Inc. New York. RobusteUi, F., J. L. McGough and D. Bouet. 1963. Relationship between avoidance conditioning and maze learning. Psychol. Rep, 13:103-106. Wickert, D. A. and G. R. Bart. 1966. Studies of learning ability in young pigs. J. Anita. Sci. 25:1280. WiUham R. L., G. G. Kares and D. C. Henderson. 1964. Partial acquisition and extinction of avoidance response in two breeds of swine. J. Comparative and Physiological Psychol. 57:117.
Downloaded from https://academic.oup.com/jas/article-abstract/40/3/573/4668068 by Iowa State University user on 23 January 2019
measures o f avoidance learning were associated w i t h different principal-components, the principal-components analyses verify the conclusion made earlier that maze learning and avoidance learning are separate p h e n o m e n o n .
579
(1962), Willham et al. (1964) and Kratzer (1965) used pigs as a model for studying the effects of x-irradation on learning ability of humans. Barnes et al. (1970) and Hammel (1973) used pigs as a model for studying the effects of protein deficiency on learning ability of humans. Several scientists have found factors that affect learning abilities of pigs. Wickert and Barr (1966) reported significant breed and sex differences in the ability of pigs to perform in a T-maze. Kratzer (1969a) also reported a significant difference in avoidance learning ability of Hampshire and Duroc breeds of pigs. Research by Baldwin and Ingram (1967) indicates that pigs may be conditioned to press a switch with their snouts and obtain heat from an infra-red lamp when "housed in a cold environment. The use of certain learning procedures may aid researchers in determining which pigs would most effectively control their environment. Kratzer (1971) suggests learning ability should be measured on several tasks to avoid inferences about learning that may apply only to a specific task. The number of techniques for measuring learning in pigs is limited. Karas et al. (1962) presented results with a shock-avoidance apparatus in which pigs were conditioned to jump a hurdle in response to a buzzer. Wickert and Barr (1966) reported on the performance of pigs in a T-maze. Pigs were isolated from their dams and then allowed to go through the maze. Time spent in the maze was the response criterion. The isolation of the pig from its dam and littermates was the driving stimulus. Additional quantitative procedure for measuring learning in pigs are needed. This research was done to study water-maze learning as a technique for measuring learning
573 JOURNAL OF ANIMAL SCIENCE, vol. 4 0 , n o . 3, 19"/5
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AVOIDANCE AND MAZE LEARNING IN PIGS 1
574
HAMMELL, KRATZER AND BRAMBLE
Experimental Procedure One hundred-twenty Hampshire x Yorkshire crossbred pigs, four pigs randomly selected from each of 30 litters, were tested for learning ability at 21 days of age in a Warner-type shuttle box adapted for swine. It consisted of a 1.83 x .61 x .61 m plywood box divided in the center by a 12.7 cm wooden barrier. The grid floor was constructed of 1.27 cm square, chrome plated bars spaced 1.27 cm apart. The floor was connected to a control box which activated the conditioned and unconditioned stimuli. The conditioned stimulus was a telephone buzzer attached to the shuttle box. The unconditioned stimulus was a sub-tetanizing level of shock delivered to the feet of the pigs via the grid floor. The response to be conditioned was movement over the central barrier. For a detailed explanation of the apparatus see Willham et al. (1964). The procedure for testing a 21-day-old pig in the shuttle box was as follows: (1) wet the pig's feet, (2) place the pig in the shuttle box on the right side of the central barrier, (3) activate the grid-half occupied by the pig, (4) start the trial with the sound of a buzzer for 6 sec, (5) if the conditioned response has not occurred, apply shock until the pig has cleared the central barrier with its front feet or a limit of 99.9 sec has elapsed. The pig could receive shock for a maximum of 93.9 sec, (6) 12-see inter-trial interval, (7) repeat steps 3 through 6 five times on the first 2 test days and 10 times on the third test day. Steps 4 through 6 were controlled automatically by instrumentation. The criteria used as measures of avoidance learning were adopted from Kratzer (1965) and were number of avoidances and escape latencies on the third day of testing. An avoidance was defined as the pig's jumping over the 12.7 cm central barrier in response to the 6.0-sec warning buzzer to avoid foot shock. Escape latency was defined as the time interval from unconditioned stimulus until response. The average escape latency was calculated because
the number of escapes, 10 minus the number of avoidances, could vary from pig to pig. Every pig in this experiment had at least one escape. Testing for avoidance learning ability was started when the pigs were 19 days of age. At 45 days of age pigs were tested in a three-choice-point water-maze. The maze was in a galvanized tank 9.14 m long, 2.44 m wide, and .61 m deep and filled with water. To prevent pigs from jumping out of the tank, galvanized sheet metal was placed around the tank creating a .61 m vertical extension. A diagram of the tank is presented in figure 1. The study was done in a randomized complete block design with litters as blocks and four maze patterns as treatments. One pig from each litter was randomly assigned to each of four maze patterns. Two alternating and two non-alternating patterns were chosen from the eight possible patterns. The alternating patterns of left-right-left and right-left-right are presented in figure 2. The non-alternating patterns of left-left-left and right-fight-right are pre-
iJ
9.2 Meters
w
1 v
2.4 Meters Figure 1. Diagram of Water-Maze
Downloaded from https://academic.oup.com/jas/article-abstract/40/3/573/4668068 by Iowa State University user on 23 January 2019
in pigs and specifically to determine which pattern or patterns in a water-maze would reflect maximum differences in learning ability. In addition, the relationship among measures of avoidance learning and water-maze learning was studied.
AVOIDANCE OF MAZE LEARNING IN PIGS
--
|
I
I
to~J
iii
Results and Discussion
jo'
---:;/----
Left--Right-Left
Totals were obtained for the three trials of a given day. The data were analyzed using analysis of variance, correlation and principal component techniques. The computer programs, Statistical Analysis Systems (Barr and Goodnight, 1971) and Univariate and Multivariate Analysis of Variance and Covariance: A Fortran IV Program (Finn, 1968), were used in analyzing the data.
,
, ,
Right-Left-Right
Figure 2. Alternating Maze Patterns
sented in figure 3. Learning ability was defined as the pig's ability to maneuver through three choice-points evenly spaced throughout the tank. The procedure for testing water-maze learning ability of pigs as follows: (1) pigs were tested 3 successive days with three trials daily with a maximum trial length of 2 min; (2) on day 1, pigs were conditioned to go through the water-maze and not allowed to retrace. Either a left or right choice at any choice-point allowed escape; (3) on day 2, pigs were introduced to their assigned escape pattern described in figures 2 and 3; (4) day 3 was repetitious of day 2. The criteria selected to reflect learning in the water-maze were total errors, total latency. These criteria were recorded on both days 2 and 3 of testing. An error was defined as swimming through a choice-point in the water-maze which would not allow escape, and a correct response was defined as swimming through a choice-point which would allow escape. Latency was defined as the time interval from entry into the tank until exit from the tank and could not exceed 2 min for any trial.
The means of avoidance learning scores on day 3 and maze learning responses on days 2 and 3 are presented in tables 1 and 2, respectively. On day 2 of testing in the water-maze, significantly more errors and latency occurred on non-alternating than on alternating patterns. Differences encountered with these maze patterns are possibly due to the design of the maze. The alternating patterns shown in figure 3 show that the second correct choice-point and the third correct choice-point in the maze are in a straight line with the movement of the pig through the maze. With the non-alternating patterns the pigs
Left- Left- Left R ight- R ight- Right Figure 3. Non-Alternating Maze Patterns
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i
575
576
HAIVIMELL, K R A T Z E R AND BRAMBLE
TABLE 1. MEANS OF AVOIDANCE LEARNING SCORES - DAY 3
Avoidances
2,53 3.00 2.70 2.60
79.4
Avg e s c a p e latency, sec
2,86 3.03 3.16 3.89 100.3
aCoefficient o f variation = s / ~ (100).
must change their direction of movement to prevent errors. Consequently, if a pig's desire is to take the most direct route through the maze it would make fewer errors and probably spend less time on alternating patterns than on non-alternating patterns. Comparisons among patterns on day 3 showed no significant differences for total errors and total latency. The performance of pigs on the non-alternating patterns was the same as the performance shown by pigs on the alternating patterns. Learning is reflected when an animal
TABLE 2. MEANS OF WATER-MAZERESPONSES ON DAYS 2 AND 3 Maze pattern Mazelearning
Maze learning
Total errors
8.03 5.40 4.83 7.30b49.9
Total corrects Totallatency
8.03 8.40 9.30c8.87 25.8 4.62 3.94 3.42 4.41d29.9 Day 3
Total errors
5.47 e 5.97 5.53 4.37 f 48.2 9,13 9.40 9.30 9.30 12.4 2.93 3.08 3.21 2.63 g38.9
Totallatency
Maze pattern
LLL LRL RLR RRR C.V. a Day 2
Total corrects
TABLE 3. COMPARISONSOF DAY 2 AND DAY 3 MEANS OF WATER-MAZERESPONSES
aCoefficient o f variation = s/x (100).
b8.03 + 7.30 significantly (P < .01) greater than 5.40 + 4.83. c 9 . 3 0 significantly (P < .10) greater than 8.40.
d4.62 + 4.41 significantly (P < .01) greater than 3.94 + 3.42.
e5.47 significantly (P < .10) greater than 4.37. f 5 . 9 7 + 5.53 significantly (P < .10) greater than 5.47 + 4.37. g3.08 + 3.21 significantly (P < 2 . 9 3 + 2.63.
,10) greater than
LLL LRL
RLR
RRR
4.83 9.30 3.42
7.30 8,87 4,41
Day 2 Total errors Total corrects Total latency
8.03 8.03 4.62
5.40 8,40 3,94 Day 3
Total errors
5,47a 5.97
5.53
4.37 b
Total corrects
9,13c 9.40d
9.30
9.30
Total latency
2,93 e 3.08 g
3.21
2.63f
a5.47 significantly (P < .01) less than 8.03, b4.37 significantly (P < .01) less than 7.30. c9.13 significantly (P < .05) more than 8.03. d9.40 significantly (P < .05) more than 8.40. e2.93 significantly (P < .01) less than 4,62, f2.63 significantly (P < .01) less than 4.41. g3.08 significantly (P < .01) less than 3.94,
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Maze pattern Avoidance learning LLL LRL RLR RRR C.V. a
changes its responses in an adaptive manner. Comparisons were made between responses of day 2 and day 3 in the water-maze to determine if learning had occurred. If learning occurred the total errors and latency should decrease and the total correct responses should increase from day 2 to day 3. Since differences among patterns were inconsistent from day 2 to day 3, the comparisons between days were done separately for each maze pattern. Changes in responses from day 2 to day 3 are shown in table 3. In general, learning occurred on the alternating patterns but not on the non-alternating patterns, with the exception that, even though an increase in total corrects was observed on the right-right-right pattern it was not statistically significant. With regard to changes in responses on the alternating patterns, pigs on the left-left-left pattern showed significant increase in total corrects and a significant decrease in total latency. But pigs on alternating patterns did not show a decrease in errors; therefore, alternating patterns are not recommended for measuring learning abilities. Presented in tables 4 and 5 are the correlations of avoidance learning responses on day 3 and water-maze scores on day 2 and 3, respectively. There were significant differences
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AVOIDANCE OF MAZE LEARNING IN PIGS TABLE 4. C O R R E L A T I O N S AMONG MEASURES OF AVOIDANCE L E A R N I N G AND WATER-MAZE L E A R N I N G ON DAY 2. A D J U S T E D F O R LITTERS AND P A T T E R N .
Maze learning Total errors Total corrects
Avoidances
Maze learning
Escape
Total
latency
errors
-- .03
.10
.15
-- .06
-- .06
.02
--
Total corrects
--.45**
Total latency
.65** --.38**
**P < .01.
among litters (P < .05) for water-maze learning on day 3 and significant differences among maze patterns on day 2 (P < .05). Therefore, correlations were adjusted for differences in maze patterns and litters. The correlation (r = -.34) between avoidances and average escape latency was significantly different from zero (P < .01). Pigs that make more avoidances also make faster escapes from shock. No significant correlations were observed between avoidance learning criteria and maze learning criteria on day 2 or 3 of testing. This finding is in agreement with previous results for pigs by Hammell (1973). Robustelli et al. (1963)found no significant correlation in rats between avoidance learning and maze learning. Their explanation applies to the results of this experiment and to quote: "The lack of correlation between the performances in the two tests might be attributed both to the different m o t i v a t i o n . . , and sensory requirements of the two tasks." In this experiment avoidance learning required perception of an auditory cue to avoid punishment whereas water-maze learning required spatial discrimination to escape from water. Principal-components analyses were used to study the relationships within the intercorrelations of avoidance and maze learning variables. In brief, a principal-component analysis reduces a matrix of correlations by extracting new
TABLE 5. CORRELATIONSAMONG MEASURES OF AVOIDANCE LEARNING AND WATERMAZE LEARNING ON DAY 3, ADJUSTED FOR LITTER AND PATTERN Avoidance learning
Avoidance learning
Maze learning
Escape Total Total Avoidances
latency
errors corrects
Escape latency
--
.34**
Maze
learning: Total errors Total corrects Total latency **P~.01.
-- .10
.06
.08
-- .02
-- .02
-- .05
--
-- .06
.71"*
.02
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Avoidance learning
variables called principal components which are correlated with the original variables but independent of each other. The first principalcomponent accounts for maximal variance among the original variables. The second principal-component accounts for maximal residual variance from the first principal-component. The third accounts for the residual from the first and second component, and so forth. By examining the correlations between the original variables and the principal-components one decides which variables overlap and which variables are separate. For a through explanation of principal-components analysis, see Overall and Klett (1972). Table 6 shows two principal-components for day 2. The first component was identified with maze learning by its significant ( P < .01) correlations with total errors (.87), total corrects ( - .69) total latency (.85). The second component was identified with avoidance, learning by its significant (P < .01) correlations with avoidances ( - .84) and average escape latency (.76). Table 7 shows three significant principal-
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HAMMELL, K R A T Z E R AND BRAMBLE TABLE 6. PRINCIPAL-COMPONENTCORRELATIONS OF LEARNING SCORES ON DAY 2 Principal-component
Criteria
1
3
4
5
-- .02
-- .84**
.33
.41
.05
.16
.76**
.56
.29
.07
.03 .26 .01 1.36 27.18
--.17 -- .50 -- .33 .80 16.07
.21 .46 .11 .52 10.44
-- .40 --.01 .40 .33 .33
66.91
82.98
93.42
100.00
Maze learning Total errors Total corrects Total latency Eigenvaluea % of total variance Cumulative % of variance
.87** -- .69** .85** 1.99 39.73 39.73
aEigenvalues greater than 1 indicate a significant principal component. * * C o r r e l a t i o n s s i g n i f i c a n t (P ~ . 0 1 ) f o r values ~ . 5 0 .
components for day 3. The first principal component was identified with maze learning from its significant (P ( . 0 1 ) correlations with total errors (.93) and total latency (.91). This component was a reflection of slower times for those pigs that made more errors. The second principal-component was identified as an avoidance learning component because it was significantly (P ( . 0 1 ) correlated with avoidances ( - .81) and average escape latency (.80). Total corrects was significantly ( P ( . 0 1 )
correlated with the third principal-component on day 3. This was unlike the results from day 2 because on day 3, total corrects had small nonsignificant correlations with total errors and total latency. Since total errors and total latency appears to be independent of total corrects and total corrects did not increase significantly from day 2 to day 3, total corrects should not be used as a measure of learning. Since measures o f maze learning and
TABLE 7. PRINCIPAL-COMPONENTCORRELATIONS OF LEARNING SCORES ON DAY 3 Principal-component Criteria Avoidance learning Avoidances Average escape latency Maze learning Total errors Total corrects Total latency Eigenvaluea % of total variance Cumulative % of variance
1
2
3
4
5
-- .14 .08
-- .81"* .80**
-- .06 -- .22
.56 .55
.93** -- .04 .91"*
-- .01 .15 -- .18
-- .03 .97** .09
.00 .15 .04
-- .37 --.04 .36
1.71 34.31
1.35 26.06
1.01 20.24
.65 13.00
.27 5.49
34.31
61.27
81.51
94.51
100.00
aEigenvalues greater than 1 indicate a significant principal component. * * C o r r e l a t i o n s s i g n i f i c a n t ( P ~ . 0 1 ) f o r values ~ . 5 0 .
-- .05 .03
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Avoidance learning Avoidances Average escape latency
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A V O I D A N C E O F M A Z E L E A R N I N G IN PIGS
Literature Cited Baldwin, B. A. and D. L. Ingrain. 1967. Behavioral thermoregulation in pigs. Physiol. and Behav. 2:15. Barnes, R. H., A. U. Moore and G. W. Pond 1970. Behavioral abnormalities in young adult pigs caused by malnutrition in early life. J. Nutr. 100:149. Barr, A. J. and J. H. Goodnight, 1971. Statistical analysis system. North Carolina State University, Raleigh. Finn, J. D. 1968. Univariate and multivariate analysis of variance and covariance: a fortran IV program. State University of New York, Bufffalo.
HammeU, D. L. 1973. Part I. Effect of protein restriction on reproduction in gilts and performance and learning of their offspring. Ph.D. Thesis. University of Kentucky, Lexington. Karas, G. G., R. L. Willham and D. F. Cox. 1962. Avoidance learning in swine. Psychol. Rep. 11:51. Kratzer, D. D. 1965. Learning behavior in swine. Dissertation Abstr. 26:4927. Ph.D. Thesis. Iowa State University, Ames. Kratzer, D. D. 1969a. Effects of age on avoidance learning in pigs. J. Anim. Sci, 28:175. Kratzer, D. D. 1971. Learning in farm animals. J. Anim. Sci. 32:1268. Overall, J. E. and C. J. Klett. 1972. Applied multivariate analysis. McGraw-HiU Book Co., Inc. New York. RobusteUi, F., J. L. McGough and D. Bouet. 1963. Relationship between avoidance conditioning and maze learning. Psychol. Rep, 13:103-106. Wickert, D. A. and G. R. Bart. 1966. Studies of learning ability in young pigs. J. Anita. Sci. 25:1280. WiUham R. L., G. G. Kares and D. C. Henderson. 1964. Partial acquisition and extinction of avoidance response in two breeds of swine. J. Comparative and Physiological Psychol. 57:117.
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measures o f avoidance learning were associated w i t h different principal-components, the principal-components analyses verify the conclusion made earlier that maze learning and avoidance learning are separate p h e n o m e n o n .
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