Multi-task integration facilitates implicit motor learning

Introduction: In this study we explore how dual task integration, triggered by structural similarity of the primary and secondary task, facilitates implicit motor learning. We were particularly interested in how manipulating motor load in a dual-task situation affects learning of a constant segment embedded in a pursuit tracking task. Furthermore we examined if dualtask effects could be attributed to task integration by temporally correlating task characteristics and increasing difficulty of primary and secondary task. Method: Whilst in Experiment 1 one group of participants, the “single group”, performed a pursuit tracking task only, another (the “random”) group executed the tracking task while simultaneously counting randomly presented high-pitch tones plus ignoring random low pitch tones. The last group, the structure group, received random low-pitch tones plus high-pitch tones that were temporally coupled to the tracking task and occurred 250ms before each extreme of the curve.
In Experiment 2 the motor difficulty of the secondary task was increased. Participants now had to tap one foot on high pitch and the other foot on low pitch tones. In Experiment 3 the difficulty of the primary task was also increased by instructing participants to use their nondominant hand. Results: Results indicate that implicit motor learning depends on the difficulty and similarity of both the primary and secondary tasks. Learning is hampered in the presence
of a dual task but only when there is no structural similarity between primary and secondary task and no stringent sensory-motor load forcing participants to exploit optimization strategies. Our results support theories of task integration in terms of beneficial effects of temporal correlation between tasks. Other types of integration such as predictability or automaticity need further research.