Abstract
We studied the dynamics of lexical decisions by asking participants to categorize lexical and nonlexical stimuli and recording their mouse movements toward response buttons during the choice. In a previous report we revealed greater trajectory curvature and attraction to competitors for Low Frequency words and Pseudowords. This analysis did not clarify whether the trajectory curvature in the two conditions was due to a continuous dynamic competition between the response alternatives or if a discrete revision process (a "change of mind") took place during the choice from an initially selected response to the opposite one. To disentangle these two possibilities, here we analyse the velocity and acceleration profiles of mouse movements during the choice. Pseudowords' peak movement velocity occurred with 100ms delay with respect to words and Letters Strings. Acceleration profile for High and Low Frequency words and Letters Strings exhibited a butterfly plot with one acceleration peak at 400ms and one deceleration peak at 650ms. Differently, Pseudowords' acceleration profile had double positive peaks (at 400 and 600ms) followed by movement deceleration, in correspondence with changes in the decision from lexical to nonlexical response buttons. These results speak to different online processes during the categorization of Low Frequency words and Pseudowords, with a continuous competition process for the former and a discrete revision process for the latter.
Highlights
Lexical decisions have been extensively studied in cognitive psychology and neuroscience, but most studies focused on the analysis of response time under different conditions
We conducted a kinematic study of mouse movements during lexical decisions with the aim to understand how such decisions unfold dynamically in time and whether the underlying decision process can be described as a continuous competition between response alternatives or a discrete process with sharp changes of mind [12,13,14]
We have previously reported the analysis of the spatial aspects of the mouse movements, which revealed spatial attraction toward the opposite category for Low Frequency words and Pseudowords, which have higher ambiguity compared to High Frequency words and Letters Strings [10]
Summary
Lexical decisions have been extensively studied in cognitive psychology and neuroscience, but most studies focused on the analysis of response time under different conditions (e.g., lexical vs. non-lexical stimuli) (see [1,2]). Recent studies using continuous kinematic measures (i.e., measuring eye or mouse movements during the choice) permitted to shed light on the dynamic properties of the moment-to-moment decision process and have been applied to a number of paradigms that include numerical and colour comparisons, categorization of ambiguous figures, and semantic categorization, among others [3,4,5,6,7]. Tracking Second Thoughts during Visual Lexical Decision
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