Abstract
Ongoing debate surrounds the capacity and characteristics of the focus of attention. The present study investigates whether a pattern of larger recency effects and smaller primacy effects reported in previous working memory studies is specific to task conditions used in those studies, or generalizes across manipulations of task-demand. Two experiments varied task-demands by requiring participants to remember lists of letters and to then respond to a subsequent two-item probe by indicating either the item that was presented later in the list (judgment of recency) or the item was presented earlier (judgment of primacy). Analyses tested the prediction that a WM task emphasizing later items in a list (judgment of recency) would encourage exaggerated recency effects and attenuated primacy effects, while a task emphasizing earlier items (judgment of primacy) would encourage exaggerated primacy effects and attenuated recency effects. Behavioral results from two experiments confirmed this prediction. In contrast to past studies, fMRI contrasts revealed no brain regions where activity was significantly altered by the presence of recency items in the probe, for either task condition. However, presence of the primacy item in the probe significantly influenced activity in frontal lobe brain regions linked to active maintenance, but the location and direction of activation changes varied as a function of task instructions. In sum, two experiments demonstrate that the behavioral and neural signatures of WM, specifically related to primacy and recency effects, are dependent on task-demands. Findings are discussed as they inform models of the structure and capacity of WM.
Highlights
A wide variety of research suggests strict limits on the mind’s ability to maintain and manipulate information over the short term—an ability often referred to as working memory (WM; e.g., Luck and Vogel, 1997; Cowan, 2001; McElree, 2006)
The magnitude of the recency effect was calculated by subtracting the reaction time on correct recency trials from the reaction time on correct middle trials, dividing this value by the reaction time on correct middle trials, and multiplying the product by 100. Accuracy for both task-types was well above chance (JOR: M = 0.85, SD = 0.07; judgment of primacy (JOP): M = 0.86, SD = 0.07) and average reaction times in milliseconds for correct trials were as follows www.frontiersin.org η2p = 0.57], a main effect of serial position [F(3, 57) = 19.19, p < 0.0005, η2p = 0.77], and an interaction between task and serial position [F(3, 57) = 9.21, p = 0.001, η2p = 0.62]. These analyses confirm performance differences associated with the serial position of the correct response, and the interaction of task and serial position found in the reaction time data suggests that serial position dynamics are not identical across tasks
In judgment of recency (JOR) there was no significant primacy effect [e.g., primacy trials and middle trials were equivalent, F(1, 19) = 0.75, p = 0.39, η2p = 0.04] but a significant recency effect [recency trials were faster than middle trials, F(1, 19) = 18.44, p < 0.0005, η2p = 0.49], while in JOP there was a significant primacy effect [primacy trials were faster than middle trials, F(1, 19) = 57.71, p =< 0.005, η2p = 0.75], but no recency effect [recency trials and middle trials were equivalent, F(1, 19) = 2.57, p = 0.13, η2p = 0.12]
Summary
A wide variety of research suggests strict limits on the mind’s ability to maintain and manipulate information over the short term—an ability often referred to as working memory (WM; e.g., Luck and Vogel, 1997; Cowan, 2001; McElree, 2006). The present paper explores one explanation for divergent conclusions about the architecture and capacity of WM, and concentrates on the contributions of the “focus of attention” (FOA, or the most immediate state of WM) to WM capacity (Cowan, 1995) Using both behavioral and neuroimaging (fMRI) methods, we test the hypothesis that subtle features of the tasks used to probe WM function (e.g., task instructions and response requirements) can lead to important performance differences (e.g., which item in a list is remembered the quickest), fundamental changes in the pattern of brain activity evoked by the WM task, and to different conclusions about the FOA and its involvement in WM. Primacy and recency effects reflect separate memory stores (Talmi et al, 2005) or states (Nee and Jonides, 2011), and in general the neuroimaging findings have been consistent with this interpretation
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
