Contrary to the belief that praise is a more effective form of incentive than reproof to use in the case of school children, the writer, in an experimental study 1 found that after one application the two, on the whole, were of equal value. These rather surprising results at once opened up the question of whether reproof, if used over a given period of time, would not lose some of its effectiveness. Previous studies, using the practice experiment technique with children as subjects, have shown that encouragement brought about increasingly better work throughout the period of practice, but no such studies are available to give us information in regard to the effect of the continuous use of discouragement. Kirby, 2 used 1350 New York school children from the Grades III and IV classes to determine the value of encouragement upon their performance in addition. He had each child practice adding for 75 minutes, but this time was distributed differently for the different groups. The form of encouragement used was the competition of each child with the record he made on the previous day's performance, and not rivalry with the other children of the group. The results obtained showed a median gain of 48 per cent, but as no control group was used, we have no means of determining how much of this was due to encouragement, and how much to practice.

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R IVALRY, either group or individual, has proved to be an effective incentive to increased efficiency in the fields of industry and sport. Its value for purely mental work is somewhat doubtful, as it is generally believed to increase the quantity of the work, while at the same time decreasing the quality. Because of the lack of experimental data on the subject, the writer has attempted, in the experiment reported on the following pages, to study the value of group rivalry as an incentive to increased efficiency in school work, not only from the point of view of the effect upon the quantity and quality of the work, but in its relation to age, sex and individual differences.Before giving a detailed description of the present study, an attempt will be made to summarize briefly studies made previous to this, but which deal with the same general problem. Allport, 1 in his "Social Psychology", has summarized the studies of this sort made up to the publication of his book in 1924, and this summary will be quoted here. "We may refer again to the experiment of Triplett upon rivalry in the turning of fishing reels. Forty subjects were used in this investigation. Twenty of them gained markedly in the competitive trials over their average for solitary work. Ten were little affected by the competition. These were for the most part older children. And ten actually lost in speed under the influence of rivalry. These last showed evidences of emotional excitement and a loss of motor control. Young, nervous and excitable subjects are prone to overstimulation through rivalry, with a consequent lowering of efficiency in competitive performance. Triplett found a higher percentage of girls than of boys susceptible to increase of performance through competition."The effect of rivalry, like that of social facilitation, varies inversely with the ability of the worker. In 1914 Dr. W. Moede published an account of rivalry in speed of tapping and strength of hand grip. Seventeen boys between twelve and fourteen years

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Students of child psychology have emphasized the periodicity of the play behavior of children of different ages and have investigated the forms of play which are characteristic of each age. It is the purpose of this paper to bring together in systematic form the studies which relate to the play of the different stages of development from birth to maturity.Among writers, there is no agreement as to how many play periods there are in the child's development, what names shall be applied to these periods nor how long each one of them lasts. Among the best classifications of age periods in play behavior are those of Baldwin (8), Croswell (31), Curtis (32), Gulick (50), Johnson (66), King (70), Kirkpatrick (71), Lee (72), Lehman and Witty (80), Pyle (103), Puffer (102), Reaney (104), and Wood (128).Several investigators have attempted to explain the periodicity of play in terms of its causes. Lee (72), Waddle (123), and Norsworthy and Whitley (98) ascribe the different plays of different ages to "instincts." Blanchard (10) and Gulick (50) maintain that the child's play interests depend upon chronological age, physiological age, mental age and environmental situations. Lehman and Wilkerson (78) report that chronological age is more powerful than mental age in determining the child's play behavior. Reaney (104) has subdivided the play of the childhood years into four different periods, based upon chronological age. Many investigators have stressed the fact that the transition from one form of play to another is gradual and often barely perceptible. Curtis (32), Lee (72), and Lehman and Witty (80) point out that the different play periods are not separated by distinct dividing lines.In the classification of play, the following stages of development have been arbitrarily used by the writer: (1) Babyhood (birth to three years) ; (2) Childhood (three to six years) ; (3) Youth (six to eleven or twelve years); (4) Adolescence (eleven or twelve ta twenty-one years).