This page contains information about an online mouse-tracking study investigating the development of conflict adaptation. Three groups of participants (6-7 year olds, 9-10 year olds, and adults) will respond with mouse clicks to two child-friendly versions of the Simon task (the Size-Simon and the Arrow-Simon task). The tasks are presented in two single blocks as well as an alternating block. From this experiment, both within- and across-task Congruency Sequence Effects will be analysed. **Funding** This study is funded by the Deutsche Forschungsgemeinschaft (DFG) and is part of the Research Unit FOR 2718 "Modal and amodal cognition: Functions and interactions" (https://uni-tuebingen.de/de/169941) **Associated publications** The full adult dataset is reported as Experiment 2 in: Potamianou, H. & Bryce, D. (in press). How flexible is cognitive control? (Mouse) tracking conflict adaptation across context similarities. *Psychological Research*. https://doi.org/10.1007/s00426-023-01874-0