2a. shows the median proportion of children of different age groups across the five trials of Task 1. Error bars represent 95% confidence intervals. 2b shows the individual marble insertions of 3 children chosen at random from each age cohort. Each column represents the order in which items were inserted within a single trial. Grey columns indicate trials not performed due to error-free performance in the three previous trials. Stars represent trials in which that age group performed above chance according to one-sample wilcoxen (4-year-olds: (1^{st}: W = 1, n = 9, p>0.05; 2^{nd}: W = 36, n = 12, p>0.1; 3^{rd}: W = 38, n = 12, p>0.1; 4^{th}: W = 29, n = 10, p>0.1; 5^{th}: W = 71, n = 13, p<0.05; 5-year-olds: 1^{st}: W = 12, n = 8, p = >0.05, 2^{nd}: W = 7, n = 10, p>0.5, 3^{rd}: W = 29, n = 12, p>0.1, 4^{th}: W = 63, n = 14, p = 0.05; 5^{th}: W = 82, n = 15, p<0.05; 7-year-olds: 1^{st}: W = 28, n = 9, p>0.05; 2^{nd}: W = 11, n = 9, p>0.05, 3^{rd}: W = 41, n = 9, p<0.02; 4^{th}: W = 59, n = 14, p>0.05; 5^{th}: W = 100, n = 14, p<0.001; 8-year-olds: 1st: W = 52, n = 11, p<0.05; 2nd: W = 45, n = 11, p<0.05; 3rd: W = 66, n = 11, p<0.005; 4th: W = 52, n = 11, p<0.05; 5th: W = 66, n = 11, p<0.005; 9/10-year-olds: 1st: W = 75, n = 12, p<0.005; 2nd: W = 45, n = 11, p<0.002; 3rd: W = 78, n = 12, p<0.005; 4^{th}: W = 82, n = 13, p<0.005; 5th: W = 78, n = 12, p<0.005).

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