Lexical decision and the diffusion model: An investigation into the mental lexicon
The lexical decision task is one of the most widely used tasks in psychology (Ratcliff, McKoon, & Gomez, 2004). Through the years, it has generally been used to investigate memory and lexical access (psycholinguistics). The lexical decision task is one way to study the organization and properties of the mental lexicon, how words are stored in the brain. The general assumption underlying the lexical decision task is that the speed and accuracy of responding to word stimuli indicate the efficiency with which word representations are activated or retrieved from lexical memory (Wangermakers, Zeelenberg, Steyvers, Shiffrin, Raaijmakers, 2004).
By manipulating the variables by which words themselves differ or the ways in which they are presented, we can begin to shed light on these cognitive processes by analyzing and interpreting how these manipulations affect a subject’s reaction time and accuracy in classifying a string of letters as a word or not a word. Based on the data that is collected, models can be used to represent how these manipulations affect the cognitive processes and certain theoretical inferences can be made, specifically related to the metal representation of words in the mind and how words are categorized and stored in the mind (i.e. the mental lexicon).
The factors that influence lexical access include word frequency, recency, and the presence of semantically related words and are all addressed in both types of models (search and network). By controlling and changing the variables of words or how they are presented, we can examine how these changes affect the timing of responses, which allows us to theorize about how these changes affect the processing in the mental lexicon. In three studies we manipulate the properties of words themselves, as well as manipulating conditions under which words are seen (priming) while subjects are performing a lexical decision task. We then fit the data from these investigations to the EZ Diffusion Model (Wagenmakers, van der Maas, & Grassman, 2007). By fitting the EZ diffusion to the results of the lexical decision task, do we gain insight to the cognitive processes of facilitation? The EZ diffusion may lend psychological plausibility of describing a response to manipulations of the lexical decision task.
