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The acquisition, maintenance, and extinction of autoshaped responding in pigeons were studied under partial and continuous reinforcement. Five values of probability of reinforcement, ranging from .1 to 1.0, were combined factorially with five values of intertrial interval ranging from 15 to 250 sec for different groups. The number of trials required before autoshaped responding emerged varied inversely with the duration of the intertrial interval and probability of reinforcment, but partial reinforcement did not increase the number of reinforcers before acquisition. During maintained training, partial reinforcement increased the overall rate of responding. A temporal gradient of accelerated responding over the trial duration emerged during maintenance training for partial reinforcement groups, and was evident for all groups in extinction. Partial reinforcement groups responded more than continuous reinforcement groups over an equivalent number of trials in extinction. However, this partialreinforcment extinction effect disappeared when examined in terms of the omission of "expected" reinforcers.

BackgroundEarly childhood services have been identified as a key setting for promoting healthy eating and physical activity as a means of preventing overweight and obesity. However, there is limited evidence on effective nutrition and physical activity programs in this setting. The purpose of this study was to evaluate Munch and Move, a low-intensity, state-wide, professional development program designed to support early childhood professionals to promote healthy eating and physical activity among children in their care.MethodsThe evaluation involved 15 intervention and 14 control preschools (n = 430; mean age 4.4 years) in Sydney, New South Wales, Australia and was based on a randomised-control design with pre and post evaluation of children's lunchbox contents, fundamental movement skills (FMS), preschool policies and practices and staff attitudes, knowledge and confidence related to physical activity, healthy eating and recreational screen time.ResultsAt follow up, FMS scores for locomotor, object control and total FMS score significantly improved by 3.4, 2.1 and 5.5 points more (respectively) in the intervention group compared with the control group (P < 0.001) and the number of FMS sessions per week increased by 1.5 (P = 0.05). The lunchbox audit showed that children in the intervention group significantly reduced sweetened drinks by 0.13 serves (i.e., 46 ml) (P = 0.05).ConclusionThe findings suggest that a low intensity preschool healthy weight intervention program can improve certain weight related behaviours. The findings also suggest that change to food policies are difficult to initiate mid-year and potentially a longer implementation period may be required to determine the efficacy of food policies to influence the contents of preschoolers lunchboxes.

Food-deprived pigeons were given brief meals of grain following the presentation of a light on a response key. Pecking the key had no consequence. Virtually all of the pigeons pecked the ligated key. The number of trials prior to the first peck varied inversely with the value of the mean interval between light onsets. Trials to criterion was a negative power function of the value of the intertrial interval. The addition of a second stimulus, never followed by food, retarded the acquisition of toe keypeck, particularly at short intertrial intervals. During steady state performance, the value of two measures of response strength, rate and probability of responding, increased as a function of the duration of the intertrial interval.

There is substantial scope for childcare services to modify their policies and practices to be more supportive of child physical activity.