EXPRESS: Stimulus specificity in combined action observation and motor imagery of typing.

Combined action observation and motor imagery (AO+MI) can improve movement execution (ME) in healthy adults and certain patient populations. However, it is unclear how the specificity of the observation component during AO+MI influences ME. As generalised observation could result in more flexible AO+MI rehabilitation programs, this study investigated whether observing typing of target words (specific condition) or non-matching words (general condition) during AO+MI would have different effects on keyboard typing in healthy young adults. In Experiment 1, 51 students imagined typing a target word while watching typing videos that were either specific to the target word, or general. There were no differences in typing execution between AO+MI conditions, though participants typed more slowly after both AO+MI conditions compared to no observation or imagery. Experiment 2 repeated Experiment 1 in 20 students, but with a faster stimulus speed in the AO+MI conditions and increased cognitive difficulty in the control condition. The results showed that the slowed typing after AO+MI was likely due to a strong influence of task-switching between imagery and execution, as well as an automatic imitation effect. Both experiments demonstrate that general and specific AO+MI comparably impact ME. Additionally, slower ME following both AO+MI and a challenging cognitive task provides support for the motor-cognitive model of MI.