Latent Markov Models to Test the Strategy Use of 3-Year-Olds in a Rule-Based Feedback-Learning Task.

This study is the first to investigate how 3-year-olds learn simple rules from feedback using the Toddler Card Sorting Task (TCST). To account for intra- and inter- individual differences in the learning process, latent Markov models were fitted to the time series of accuracy responses using maximum likelihood techniques (Visser et al., 2002). In a first, exploratory study (N = 110, 3- to 5-years olds) a considerable group of 3-year olds applied a hypothesis testing learning strategy. A second study confirmed these results with a preregistered study (3-years olds, N = 60). Under supportive learning conditions, a majority of 3-year- olds was capable of hypothesis testing. Furthermore, older children and those with bigger working memory capacities were more likely to use hypothesis testing, even though the latter group perseverated more than younger children or those with smaller working memory capacities. 3-year-olds are more advanced feedback-learners than assumed.

Do infants have the horizontal bias?

A robust set of studies show that adults make more horizontal than vertical and oblique saccades, while scanning real-world scenes. In this paper we study the horizontal bias in infants. The directions of eye movements were calculated for 41 infants (M=8.40 months, SD=3.74, range=3.48-15.47) and 47 adults (M=21.74 years, SD=4.54, range=17.89-39.84) while viewing 28 real-world scenes. Saccade directions were binned to study the proportion of saccades in the horizontal, vertical and oblique directions. In addition, saccade directions were also modeled using a mixture of Von Mises distributions, to account for the relatively large amount of variance in infants data. Horizontal bias was replicated in adults and also found in infants, using both the binning and Von Mises approach. Moreover, a developmental pattern was observed in which older infants are more precise in targeting their saccades than younger infants. That infants have a horizontal bias is important in understanding infants' eye movements. Future studies should account for the horizontal bias in their designs and analyses.