Concurrent with the decline in dental caries has been an increase in the prevalence of dental fluorosis, a side-effect of exposure to greater than optimal levels of fluoride during amelogenesis. The mechanisms that underlie the pathogenesis of dental fluorosis are not known. We hypothesize that genetic determinants influence an individual's susceptibility or resistance to develop dental fluorosis. We tested this hypothesis using a mouse model system (continuous eruption of the incisors) where genotype, age, gender, food, housing, and drinking water fluoride level can be rigorously controlled. Examination of 12 inbred strains of mice showed differences in dental fluorosis susceptibility/resistance. The A/J mouse strain is highly susceptible, with a rapid onset and severe development of dental fluorosis compared with that in the other strains tested, whereas the 129P3/J mouse strain is least affected, with minimal dental fluorosis. These observations support the contribution of a genetic component in the pathogenesis of dental fluorosis.

The effect of adult social reinforcement on the cooperative play of a five-year old girl in a preschool setting was assessed under two conditions: (1) presented randomly throughout the school day, and (2) presented contingent on cooperative play. Only in the latter condition was a significant change in cooperative play observed.

Adult social reinforcement and access to materials in the preschool were made contingent on the verbalizations of a 4-yr-old Negro girl with an extremely low frequency of talking. Though the teachers' social attention was always given immediately for all spontaneous speech, if the child's spontaneous verbalizations were requests for materials, those materials were withheld until she had responded to the teachers' questions about those materials. When she was silent, the teachers withheld their attention and the materials. A high frequency of verbal behavior was quickly established. When both teacher attention and materials were provided only when the child was not verbalizing, the child's frequency of talking immediately decreased. When social attention and materials were again made contingent upon spontaneous speech and answering questions, the child's frequency of talking quickly increased to its previous high level. The content of the child's verbal behavior which increased was primarily a repetition of requests to the teachers with little change noted in the non-request verbalizations, or verbalizations to other children. A further experimental analysis demonstrated that social interaction per se was not the reinforcer which maintained the increased verbalization; rather, for this child, the material reinforcers which accompanied the social interaction appeared to be the effective components of teacher attention.Children in an economically deprived area lack many skills which would enable them to function effectively in the public schools or in the middle-class society, of which public schools are an integral part. The most damaging deficiency appears to be a lack of verbal and language skills (Bereiter and Engelmann, 1966) Harris, Wolf, and Baer, 1964). These studies, which investigated the relationship between the behaviors of teachers and the behaviors of preschool children, have indicated that the "attention" of the teacher can function as a strong reinforcer to establish, modify, and maintain the behavior of preschool children.This development has provided information about principles of behavior and how these principles affect human behavior. It has also provided a technology for therapeutic intervention in human problems and for increasingly more sophisticated analyses of human behavior. The present study was undertaken to increase the frequency of verbal- During free-play periods, the children could move from one to another of the unstructured activities usually found in preschool programs such as a block area, a doll area, a painting area, or a sand box. Some materials such as blocks were available to the children, and others such as paint were dispensed by the teachers. During the free-play periods, the three teachers always attended to, talked to, and interacted with the children and occasionally provided snacks (fruit, cookies, crackers, etc.) contingent upon generally appropriate play behavior. PROCEDURES AND RESULTS RecordingThree observers recorded data during the morning free-play periods, an...