ROBERT DEITCHMAN, PATRICK MALONEY, KEVIN WALSH AND RICHARD H. HAUDE. University of Akron

Transcription

1 Perceptzlal and Motor Skills, 1977,45, Perceptual and Motor Skills 1977 VISUAL OBSERVING BEHAVIOR IN THE ALBINO RAT: EFFECTS OF NATURE AND COMPLEXITY OF VISUAL STIMULI AND STAGE OF ESTRUS1 ROBERT DEITCHMAN, PATRICK MALONEY, KEVIN WALSH AND RICHARD H. HAUDE University of Akron S~mnzary.-The effect of varying levels of complexity within two types of visual stimuli on observing behavior of albino rats (60 females, 30 males, CD Strain, Charles River) was examined. Measures of frequency and duration of looking, as well as measures of general activity, were recorded. Differences in duration of observing as a function of group membership and type of stimuli were obtained. Activity was affected by the level of complexity. A re-examination of the concept of complexity is suggested. Further delineation of variables affecting observing behavior is also needed. Sex differences in various nonsexual behaviors of rodents have been reported since the 1920's. In adult rats females show cyclical variations in activity levels while males do not ( Wang, 1923). These variations have been shown to be correlated with the estrous cycle in female rodents, since prior to achieving sexual maturity these differences fail to appear and also when females are gravid or during post partum lactation, differential activity levels are not found. Following the demonstration of the relationship between estrous cycling and general activity level, other avenues of research relative to the estrous cycle have since been explored. Sloanaker (1925) reported a significant decrease in food intake for female rodents in the estrous phase of their cycle. More recently Tarttelin and Gorski ( 1971 ) have found this rhythmic reduction of food intake to be linked to the secretion of various hormones. These authors noted that where the maximal reduction of food intake occurs, blood estrogens are at or near their maximum levels. Greater "emotionality" in female rats has also been hypothesized to occur at the estrous phase of the cycle. This position has been supported by the observation of a reduction of defecation and an increase in ambulatory activity in the open field (Anderson, 1940; Gray & Levine, 1964). However, Drewett ( 1973) has argued that the decreased amounts of defecation exhibited by estrous rats merely reflects the reduction in food consumption caused by the elevated levels of blood estrogen, while Archer (1973; Birke & Archer, 1975) has objected to the dependent variables used to assess the dimensions of "emotionality." For example, open-field defecation, a common index of emotionality, showed little 'The authors wish to express their appreciation to Philip Hovatter and Albert Farres for their technical assistance in siide preparation and classification.

2 1304 R. DEITCHMAN, ET AL. relationship to supposed measures of "emotionality" taken in other types of tests, e.g., emergence tests, active avoidance learning. Since it has been clearly shown that there are definite behavioral changes correlated with estrous cycling, it seems reasonable to assume that other behavioral changes may also be similarly related. The present study was addressed to the question of the effects sf estrous on looking or visual observing behavior since sex differences in looking behavior as a function of visual stimulus complexity are known to occur. As an alternative to1 older approaches to the study of visual stimulus complexity, we propose a technique developed by Burkholder, Deitchman, Haude, and Sanders ( 1975) which allows a more direct measurement of looking or observing behavior. This technique relies upon an infrared photobeam within a small observing chamber in the larger experimental chamber. The rat must insert its head into the observing chamber to observe the stimulus being projected by a slide projector. The frequency and duration of looking at any given slide are then recorded electronically. Preferences are established by recording the frequency of approaches made to the slide and their corresponding durations. An activity platform is also installed in the experimental chamber so that all three measures may be recorded simultaneously. The entire apparatus has been fully described elsewhere (Burkholder, et at., 1375). METHOD Subjects were 60 female and 30 male CD Strain Charles River Albino rats, each 92 days of age at the beginning of testing. All were individually housed. Two categories of visual stimuli were included in the array presented to each animal, geometric slides and social slides. The geometric slides showed arrays of 1, 2, 5, 15, or 25 elements arranged in a black and white checkerboard pattern. The amount of black vs white surface was equivalent within each slide. Equal illumination levels for all colmplexities were confirmed by use of a Macbeth Illuminometer. The social slides depicted a close-up photograph of either one or two rats engaged in various postures such as grooming, naso-anal sniffing, aggressive behavior, mounting, etc. These slides were photographed against a uniform black field to control for extraneous visual stimuli. As with the geometric slides, five levels of social complexity, all equated for illumination level and determined by the number of animals in the siide and the postures engaged in, were used. From least to most complex the content of the social slides was a single animal, a pair of animals together, not touching, a pair of animals, one engaged in a naso-anal sniff, a pair of animals engaged in a mutual naso-naso sniff, a pair of animals standing on their hind legs engaged in an aggressive display. This ordering was determined by four independent judges. Interrater reliability was 95. Females were randomly assigned to either the estrous or non-estrous group. Estrous states were established through vaginal smearing and microscopic exarni-

3 VISUAL OBSERVING BY ALBINO RATS 1305 nation of the cellular composition of the smears according to procedures described by Wang (1923).2 All females were tested in the visual looking apparatus on the appropriate night of the estrous cycle. Two different sequences of slide presentation were used. Sequence I used 15 geometric slides ( 3 of each of the 5 complexity levels) presented prior to the 15 social slides (also 3 of each of the 5 con~plexity levels). The order of the 15 slides within each stimulus category was established by a table of random numbers. Sequence I1 was the identical procedure with the exception that social slides were presented first. Each slide was presented for 30 sec. Between presentations of the social and geometric slides there was a 30-sec. blackout period. Males and females were randomly assigned to Sequence I or Sequence 11. RESULTS AND DISCUSSION The three measures, frequency of observing, duration of observing, and general activity, were each subjected to analysis of ~ariance.~ The mean and standard deviation for each measure for the various groups and type and level of complexity are shown in Table 1. These analyses showed, first, that the sequence of stimulus category presentation (Sequence I vs Sequence 11) had no significant effect on any of the three measures. Second, there were significant differences among the three groups in duration of observing (Fz,si = 3.27, p <.O5). Non-estrous females exhibited TABLE 1 MEAN FREQUENCY, DURATION, AND ACWITY DATA AVERAGED OVER TRIALS GROUP, TYPE, AND LEVEL OF COMPLEXITY AND CORRESPONDING STANDARDEVIATIONS FOR Frequency Duration Activity M SD M SD M SD Group* Male Estrous Non-estrous TYW Social Geometric Level *.n = 30 for each group. "Induction of pseudopregnancy in female rats may be carried out by mechanical stimulation of the cervix uteri. Occasionally it may result from taking vaginal smears. Some researchers have abandoned using smears for this reason and determine estrus level by behavioral observation. The authors feel that smears provide a much more precise estimate of stage of estrus and note low reliabilities of behavioral observations in exact determination of estrus. 3All analyses were performed by use of BMD08V-Analysis of Variance.

4 1306 R. DEITCHMAN, ET AL. the largest duration (M = 7.27), followed by estrous females (M = 6.47) and males (M = 5.06). The duration measure also was significantly different between the two slide categories (Fl,si = 5.58, p <.025). Social slides (M = 6.79) were viewed for greater duration than geometric slides (M = 5.75 ). No significant differences in frequency of observing were noted. Third, there were no significant differences in the activity measures among the three groups. Despite the failure to replicate earlier research showing significant activity differences between estrous and non-estrous females, estrous animals did have higher mean activity scores (M = ) than non-estrous animals (M = ). Significant differences in activity were shown among the five complexity levels (F4,X48 = 5.37, $ <.005). No difference in activity appeared between social and geometric slides. There were no significant interactions in any of the analyses. The results indicate that duration of observing behavior is affected by the type of stimulus material used. Preferences for social over geometric slides were established. Also the physiological state of the organism (estrous-non-estrous) affects observing behavior. Sex differences along this dimension also exist. The level of complexity present in the stimulus will affect the activity level of the animal. The possibility exists that variations in activity levels between estrous and non-estrous females may be overridden by the type and level of complexity in the stimuli. The efficacy of using males as controls for non-estrous females should also be examined. In the present study males were not consistently more similar to non-estrous animals than estrous animals. Interestingly the content of the stimuli affects observing. Since social and geometric slides were not equivalent in the responses they elicited, research using only one content dimension may not be readily generalizable to other content dimensions. Further research examining how content affects complexity preference needs to be conducted. Clearly then the areas of preference complexity, visual observing, and a wide range of responses to visual stimulation need to be expanded. This should be done since both type and level of complexity, as well as physiological state of the organism, have been shown to affect these dimensions. Observing responses must be directly quantifiable and our current definitions of what constitutes complexity in visual stimulation needs reexamination. Perhaps instead of an a prior; arbitrary definition of complexity, we should ascertain what behaviors are elicited by various visual arrays and then define complexity in terms of these behaviors. REFERENCES ANDERSON, E. E. The sex hormones and emotional behavior: I. The effect of sexual receptivity upon timidity in the female rat. JozdrnaZ of Genetic Psychology, 1949, 56,

5 VISUAL OBSERVING BY ALBINO RATS 1307 ARCHER, J. Tests for emotionality in rats and mice: a review. Animal Behaviom, 1973, 21, BIRKE, L. I. A., & ARCHER, J. Open-field behaviour of oestrous and dioestrous rats: evidence against an 'emotionality' interpretation. Animal Behaviour, 1975, 23, BURKHOLDER, J., DEITCHMAN, R., HAUDE, R., & SANDERS, R. Observing behavior in the albino rat: a within-subjects' comparison of increasing levels of visual complexity. Perceptad and Motor Skills, 1975, 41, DREWETT, R. R. Oestrus and dioestrus components of the ovarian inhibition on hunger in the rat. Animal Behuuiozsr, 1973, 21, GRAY, J. A., & LEVINE, S. The effect of induced oestrus on emotional behaviour in selected strains of rats. Natwe, London, 1964, 201, SLOANAKER, J. F. The effect of sexual phenomena on voluntary activity in the rat. American Journal of Physiology, 1925, 71, TARITELIN, M. F., & GORSKI, R. A. Variations in food and water intake in the normal and acyclic female rat. Physiology and Behaviour, 1971, 7, WANG, G. H. The relation between 'spontaneous' activity and oestrus cycle in the white rat. Compa~ative Psychological Momgraphs, 1923, 2, Accepted November 4, 1977.