Effects of Overlap Between Consecutive Words on Speeded Typing Inform About Representation of Serial Order Within Words

Typing is an everyday activity that requires people to use the correct serial order of phonological and orthographic forms of words. The evidence until now shows that different forms of representation of serial order have mixed contributions to typing performance. It is not clear whether and how representational overlap between subsequent words impacts the speed of typing. In three experiments, we used speeded typing of six-letter words. Including conditions with secondary task load to counteract potential ceiling effects, we varied whether subsequent words had partial overlap with respect to a chaining representation (e.g., kirsch → schaum; same triplet in different position) or, in addition, overlapped with respect to a potential positional representation (e.g., berlin → dublin, same triplet in the same position). Differently from previous findings (e.g., Snyder & Logan, 2014), Experiments 1 and 2 suggest that (a) chaining as well as positional coding are involved as representations of serial order and (b) partial overlap of representation of serial order leads to costs in typing speed. Experiment 3 demonstrated that full overlap speeds up typing. Across all experiments, the overlap effects were most revealed in the latency of the first keystroke, indicating the planning of motor programs. Taken together, the results suggest that even in highly practiced tasks such as typing, the activation of representations of serial order has side effects beyond the production of the current sequence.