Shifting Attention Between Visual Dimensions as a Source of Switch Costs

Abstract

Task-switching experiments have documented a puzzling phenomenon: Advance warning of the switch reduces but does not eliminate the switch cost. Theoretical accounts have posited that the residual switch cost arises when one selects the relevant stimulus-response mapping, leaving earlier perceptual processes unaffected. We put this assumption to the test by seeking electrophysiological markers of encoding a perceptual dimension. Participants categorized a colored letter as a vowel or consonant or its color as "warm" or "cold." Orthogonally to the color manipulation, some colors were eight times more frequent than others, and the letters were in upper- or lowercase. Color frequency modulated the electroencephalogram amplitude at around 150 ms when participants repeated the color-classification task. When participants switched from the letter task to the color task, this effect was significantly delayed. Thus, even when prepared for, a task switch delays or prolongs encoding of the relevant perceptual dimension.

How Task Set and Task Switching Modulate Perceptual Processes: Is Recognition of Facial Emotion an Exception?

“…One caveat to note is that in our face perception task expression was relevant with respect to the response categories -emotional and neutral expressions were mapped onto the two responses in the face task. In the study by Elchlepp et al (2017), which showed that switching from the letter task prolonged colour processing, the ERP contrast based on the frequency (probability) of colour presentation was orthogonal (incidental) to the required 'warm/cold' colour classification (the manipulation of colour probability was also not mentioned to participants before or during the experiment). Similarly, in Elchlepp et al's (2015) Experiment 1, which showed that the ERP effect of word frequency was delayed by a switch from the perceptual (colour symmetry) task to the lexical task and strongly attenuated in the perceptual task, the lexical frequency contrast was orthogonal to the semantic categorisation task (and it was not mentioned to participants until the post-experiment debriefing).…”

“…Hence, we sought to minimise the face-letter spatial separability by: (1) superimposing relatively large transparent letter outlines on faces (see Figure 1), and (2) varying the exact size of the letter and its location on the face, whilst ensuring that the letter was always superimposed on a substantial portion of the eyes-nosemouth region of the face. Our reasoning (analogous to that of Elchlepp et al, 2015 andElchlepp et al, 2017) is that if perceptual encoding of emotional expression is independent of task-set we should find its electrophysiological 'signature' (the EEE) uninfluenced by switching from the letter task. Our analyses will also further interrogate the "automaticity" of recognition of emotional expression.…”

“…However, contrary to Meiran and Marciano’s ( 2002 ) study, they also found that increasing the CSI reduced the switch-related delay in dimension selection considerably – though it did not eliminate it. Finally, in a recent EEG study ( Elchlepp, Best, Lavric, & Monsell, 2017 ), we asked participants to classify a letter as vowel/consonant, or its colour as “warm”/“cold”. A prepared switch to the colour task (relative to repeating it) delayed, by 17 ms, an ERP marker of colour processing starting at ~150 ms following stimulus onset.…”

How to withhold or replace a prepotent response: An analysis of the underlying control processes and their temporal dynamics

“…We estimated the s-LRP latency difference between fast and slow change RT waveforms using a cross-correlation method (Elchlepp, Best, Lavric & Monsell, 2016). This method does not return an onset latency for each waveform but a value representing how much in time one waveform has to be shifted to achieve a maximal correlation with the other waveform.…”

Does Learning Influence the Detection of Signals in a Response-Inhibition Task?

“…500 ms in Experiment 1) to ensure that there was ample time for participants to reorient their attention (see e.g. Elchlepp, Best, Lavric, & Monsell, 2017).…”