Two is better than one, but mine is better than ours: preschoolers' executive function during co-play.

The current study investigated how playing with another individual may influence 3- and 4-year-olds' executive function in the Less-Is-More (LIM) task, where children point to the tray with the smaller amount of treats so as to obtain the larger amount of treats in the other tray. In Experiment 1, 35 Singaporean children were tested with a self version and a co-player-split version of the LIM task. Results showed that children appeared to be less impulsive when playing with a co-player than when playing individually. Experiment 2 further investigated how the intention of the co-player, collective profit oriented versus individual profit oriented, may influence children's executive function. In total, 96 children were tested with a self version, a co-player-share version, and a co-player-opponent version. Results showed that the co-playing facilitation effect appeared in only the co-player-opponent version. Together, the results of the current study showed that when preschoolers play with an individual who shares a common goal with them, they may become more efficient in executive control.