Anne Fleur Kortekaas-Rijlaarsdam

CHAPTER 5 102 phases consisted of (1) a fixation cross presented for 1000 ms followed by (2) two stimuli presented in the center of either visual half field presented until the child responded or a maximum of 4000 ms elapsed. The stimuli consisted of six different Greek characters (θ, γ, δ, ε, η, and ζ for version 1, and φ, α, ρ, σ, ψ, and μ for version 2) that were randomly assigned to one of six conditions (A, B, C, D, E or F). Parallel versions of the task were used to avoid test-retest effects. There were three reward probability conditions (70%, 85% and 100%), see below. Learning phase In the learning phase, participants were presented with trials containing a stimulus pair and they had to select the stimulus associated with the highest reward rate. There were three fixed pairs (AB, CD and EF) comprising of six stimuli (A-F). There were three reward probability conditions: In the “continuous reward condition” (pair AB) choosing A always resulted in a reward, while choosing B always resulted in a penalty. In the “85% reward condition” (pair CD) the reward rate associated with stimulus C was 85% (in 15% of trials, a penalty was obtained), while the reward rate of stimulus D was 15%. In the “70% reward condition” (pair EF) the reward rate associated with stimulus E was 70% (in 30% of the trials negative feedback was obtained), while the reward rate associated with stimulus F was 30%. For each child, stimuli were randomly allocated to the three conditions. A reward consisted of a ‘thumbs up’ accompanied by a picture of €0.20 coin gain, while penalty consisted of ‘thumbs down’ accompanied by a picture of €0.20 coin loss. Feedback was presented for 1500 ms. The learning phase consisted of learning blocks of 60 trials with a minimum of one and a maximum of five blocks, depending on performance rates. The learning phase was terminated when participants performed above-chance level in the learning phase (choosing the stimulus with the highest reward rate in the pairs AB, CD and EF in more than 70, 65 and 60% respectively, see Königs et al., 2016). Children that did not perform above change level after five blocks (i.e., no learning occurred), did not enter the test- phase. The dependent variable was learning task performance, which was defined as the accuracy (% correct) in the last block of the learning phase, divided by the number of learning blocks completed to satisfy learning phase criteria (higher values reflected better performance) (see (Königs et al., 2016)). Trials from the training and test phase suspected of anticipatory responses (reaction time <200 ms) were excluded (0.3% of trials). Test phase In the test phase (120 trials) participants were instructed to select the stimulus with the highest reward rate of the existing stimulus combinations (AB, CD and EF) as well