How do infants perform two-step actions, as for example reaching for a toy to place it somewhere else? Do they plan their reach based on what’s happening next? Or do they tailor their placing action based on the previous reach?

We just published a modelling paper addressing this question.

Gottwald, J.M., Gredebäck, G., & Lindskog, M. (2019). Two-step actions in infancy – the TWAIN model. Experimental Brain Research. https://doi.org/10.1007/s00221-019-05604-0.
📖 online copy (publisher, open access)

The answer is: Both! We show that in addition to planning effects, there are transfer effects when 1.5 year-olds carry out these two-step actions. In this paper, we propose a model describing movement durations in reach-to-place sequences.

Here, you can find the data related to the publication at the Open Science Framework.