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Weighted means of heritability and repeatability estimates from the prior method by age and data source Weighted means of heritability and repeatability estimates from the prior method by distance Number of racing records by year and distance from 1971-1986 Means for racing time by year and distance from 1971-1986 Summary of racing time by month and distance Frequency distributions for number of horses per race by distance Summary of racing times at the five largest tracks for each of five racing distances Frequency distributions for number of tracks per horse by distance Frequency distributions for number of tracks per sire by distance Handicap weight means and standard deviations by distance

Twenty-four yearling Quarter Horse fillies were divided into three groups (I) very limited handling, (II) intermediate handling and (III) extensive handling. At about 14 months of age, each horse was preconditioned for 2 weeks and then run in a simple place-learning T-maze test in which it had to locate its feed. Thirty trials were run daily for 20 days, with the location of the feed changed each day. To retire from the maze, a horse had to meet the criterion: 11 correct responses in 12 tries, with the last eight being consecutive. Horses in Group II required the fewest trials to reach criterion. These horses also learned more and had the highest percentage of correct responses (P less than .05). Mean trainability tended to predict learning ability; however, trainability and trials to criterion were not significantly correlated. Mean emotionality scores indicated a tendency for horses in the intermediately handled group to be less emotional than those in Group I or III. Results indicated that horses with an intermediate amount of handling scored higher on an intermediate test of learning. All handled horses scored higher on learning tests than those not handled.