Toshiaki Tachibana

Open-Field Test for Rats: Correlational Analysis

96 male rats were tested in open field in dim-light condition or bright-light condition for 3 min. per day for 5 days. The validity of 7 open-field test measures was assessed on the basis of the concept which was defined operationally using the test situation as the external criterion. Ambulation in the first 1 min. and rearing showed not only validity but also some generality. An interactive measure (ambulation in the first 1 min. and defecation) was proposed as a new significant measure. Larger intercorrelations among measures were obtained in a less stressful situation. In view of the results, an interpretation of previous conflicting results was proposed. Considerable constant factor-loading pattern across days and groups was noted, and this suggested the validity of the factor structure of an open-field test measure. Scores obtained on Day 1 showed some heterogeneity among scores obtained during 5 days.

Schemata and Attitudes toward Persons with Intellectual Disability in Japan

375 parents of pupils were asked to respond to 14 questions on attitudes toward persons with intellectual disability. About 30% of variance in attitude was explained by a set of variables. The effects of schemata concerning person with intellectual disability had a great effect on attitudes toward such persons. The guess of a greater contribution of heredity as the basis of intellectual disability and of fewer such persons in the future of their own families than in the general population was associated with greater negative attitudes toward persons with intellectual disability. As these estimations relate to teachable information, the attitudes might be improved.

Reproducibility across Experiments of Behavioral Results Obtained under Strictly Standardized Conditions: Another View of the Results of the Collaborative Behavioral Teratology Study:

The data of the Collaborative Behavioral Teratology Study were reanalyzed. The degree of reproducibility of the treatment effect across experiments was assessed as the magnitude of fluctuation in strength of association (η2) for the replication experiment. There was no evidence that fluctuation of treatment effects across experiments was greater for behavioral measures than for nonbehavioral ones, suggesting the conventional belief that low reproducibility of results in behavioral teratology reflects the low reliability of the behavior test per se is unwarranted. Although the distributions of obtained treatment effects were almost symmetric and unimodal for most measures, the ranges were considerable. Considering that experiments were conducted under strictly standardized conditions across experiments, finding of the considerable ranges indicates that inconsistency in results across experiments cannot be remedied adequately by employing solely a standardized method. Basing in the main their results in terms of conventional significance tests, research workers in the collaborative study concluded that excellent reproducibility of behavioral data was demonstrated. The logic underlying the statistically nonsignificant interaction used in the original work was examined critically. A serious limitation upon the significance test for assessing the reproducibility of results was pointed out, and a warning issued about customary reliance only on a significance test.

Significance Test in Studies of Nonrandomly Assigned Subjects: A Call for More Discussion

There is a fundamental difficulty with a significance test in studies in which subjects are nonrandomly assigned, e.g., differences in strain, sex, age groups, and species, etc. The implausibility of the assumption of random sampling and the use of the significance test in such studies is pointed out. Inference without reliance on the significance test is needed not only in studies of subjects nonrandomly assigned but also in those in which assignment of subjects is random. It is emphasized that inference without the significance test remains a standard scientific approach, in spite of the widespread use of many statistical tests. A call is made for more discussion of the problem.

LITTER EFFECTS IN OPEN-FIELD BEHAVIOR AND DISTORTION OF TYPE I ERROR RATE WITH INDIVIDUAL ANIMALS AS THE UNIT OF STATISTICAL ANALYSIS

Using open-field test data of male rats, a correlation provided an estimate of the magnitude of dependency among litter mates. A simulation experiment was performed to estimate the magnitudes of Type I error rate distortions when individual scores instead of litter mean scores were employed as the unit of statistical analysis. The results showed a rather large correlation among litter mates in defecation, latency of defecation, and latency of urination, suggesting that it is better to avoid treating the individual animal as the unit of statistical analysis. However, the magnitude of correlations in the remaining measures was negligible. As to Type I error rate, except for defecation, latency of defecation, and latency of urination, the obtained values obtained were not seriously affected. A very seriously inflated distortion in the error rate was found for body weight.

REPLY TO VORHEES' COMMENTS: WHAT IS THE PROPER UNIT OF ANALYSIS FOR THE COLLABORATIVE BEHAVIORAL TERATOLOGY STUDY DATA?

Vorhees (1989) argued critically that my reanalysis of the Collaborative Behavioral Teratology Study data was performed on the basis of improper unit of analyses. It was shown that his criticism is unwarranted. The erroneous logic underlying the collaborative studys conclusion that excellent reproducibility of data was obtained was confirmed.

CASES OF SPRAGUE-DAWLEY RATS WHICH DID NOT RESPOND TO AN 'ALARM SUBSTANCE' IN THE FORCED SWIMMING TEST

The fact found by Abel and his group that rats produce an ‘alarm substance’ while swimming was examined by employing a single-subject approach. Sprague-Dawley rats were tested in the forced swimming test situation in fresh water and in water soiled by another rat. In Exp. 1, Sprague-Dawley rats from Japan SLC, Inc. were used. No evidence of responding to the ‘alarm substance’ was found. Then, further experiments were conducted employing methods similar to those of Abel and his group. In Exp. 2, Sprague-Dawley rats from Charles River, Japan, were used. In Exp. 3, the water depth and inner diameter in a cylinder used were the same as those used by Abel and his group, and the water was soiled more thoroughly. In Exp. 4, the level of water contamination was raised to four times that employed in Exps. 1 and 2. However, the series of experiments yielded no evidence of the ‘alarm substance.’ Breeder differences among subjects might explain the discrepancy in results.