Problem solving is integral to goal-directed action—how to navigate an obstacle, open a latch, or grasp the handle of a tool. Traditionally, researchers focus on when in development children succeed at solving particular problems, but this outcome-oriented approach does not inform on underlying mechanisms. The current study focuses on how children solve problems by examining the real-time interplay among planning components. We encouraged 3- to 5-year olds (N = 32) and adults (N = 22) to grasp

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... hammer to pound a peg when the hammer handle pointed in different directions. We simultaneously recorded participants' movements, gaze, and neural activity using video microcoding, motion-tracking, head-mounted eye tracking, and EEG. When the handle pointed toward their non-dominant hand, participants had to use an adaptive underhand initial grip to implement the tool efficiently. Younger children ("non-adaptive child solvers") used a habitual overhand grip that interfered with wielding the hammer, whereas adults and older children ("adaptive child solvers") used an underhand grip. Adaptive and nonadaptive solvers differed in when and where they directed visual attention when the handle direction was revealed; neural processing prior to movement (readiness potential); and the straightness of their hand path as they initiated the reach. Non-adaptive child solvers immediately used the habitual solution and only later gathered visual information, leaving insufficient time to form a plan before acting. We suggest that the development of adaptive problem solving depends on this real-time "tug of war" between habits and information gathering and processing.