Method
Participants
In total, 45 18- to 20-month-olds (mean age = 18 months 19 days [18;19], range =
17;19–20;16, 25 girls and 20 boys) and 45 22- to 26-month-olds (mean age = 24;3,
range = 22;11–26;9, 16 girls and 29 boys)1 were randomly assigned to one of the three
conditions with the restriction that 15 infants from each age group were tested in each
condition. Participants were recruited through the local community and were primarily
middle-class volunteers.