A change of task prolongs early processes: evidence from ERPs in lexical tasks.

PublishedJournal ArticleSwitching tasks costs time. Allowing time to prepare reduces the cost, but usually leaves an irreducible "residual cost." Most accounts of this residual cost locate it within the response-selection stage of processing. To determine which processing stage is affected, we measured event-related potentials (ERPs) as participants performed a reading task or a perceptual judgment task, and examined the effect of a task switch on early markers of lexical processing. A task cue preceding a string of blue and red letters instructed the participant either to read the letter string (for a semantic classification in Experiment 1, and a lexical decision in Experiment 2) or to judge the symmetry of its color pattern. In Experiment 1, having to switch to the reading task delayed the evolution of the effect of word frequency on the reading task ERP by a substantial fraction of the effect on reaction time (RT). In Experiment 2, a task switch delayed the onset of the effect of lexical status on the ERP by about the same extent that it prolonged the RT. These effects indicate an early locus of (most of) the residual switch cost: We propose that this reflects a form of task-related attentional inertia. Other findings have implications for the automaticity of lexical access: Effects of frequency, lexicality, and orthographic familiarity on ERPs in the symmetry task indicated involuntary, but attenuated, orthographic and lexical processing even when attention was focused on a nonlexical property.Economic and Social Research Counci

The temporal dynamics of switching tasks

The topic of this thesis is cognitive control: how the brain organises itself to perform the many tasks it is capable of and how it switches flexibly among them. Task-switching experiments reveal a substantial cost in reaction time and accuracy after a switch in tasks. This "switch cost" is reduced by preparation (suggesting anticipatory task-set reconfiguration), but not eliminated. The thesis focuses on the sources of the "residual" cost. Most accounts attribute it to response selection being prolonged on a task-switch trial by task conflict, e.g. by 'task-set inertia' — persisting activation/inhibition of the previous task's S-R rules — or their associative reactivation by the stimulus. Four experiments used event-related potentials (ERPs) to determine which stages of task processing are influenced by a change in tasks, looking for delays in process-specific markers in the ERP. Experiments 1 and 2 showed that a prepared switch to a reading task from a perceptual judgement delayed early ERP markers of lexical access by a large fraction of the RT switch cost, suggesting that a substantial part of the residual cost arises in processes earlier than response selection, possibly due to task-related attentional inertia. Markers of lexical access observed in the non-lexical task were larger on switch than repeat trials, providing the first electrophysiological evidence of task-set inertia. Experiment 3 examined the effects of an unprepared switch in the same way. ERP waveforms were modulated by a switch before markers of lexical access were evident, suggesting additional processing demands compete for resources with lexical access. A simple delay, however, was not found; post-stimulus task-set reconfiguration does not just insert an extra processing stage. Experiment 4 looked for a delay in the onset of an early ERP marker of emotional processing when the task switched between categorising facial expression and classifying a superimposed letter. No such delay was found in this case, and ERP markers of emotion processing were present to the same extent in the letter task. This suggests that, given appropriate spatial attention, processing facial emotion unfolds automatically, independent of attention allocation to the facial features. Experiments 5-7 further explored the link between conflict due to processing the irrelevant stimulus dimension and the ERP post-stimulus negativity that accompanies the residual cost. The negativity could be elicited even on trials of non-switching blocks by prior training on classifying the irrelevant attribute of the stimulus using the same responses. But this effect did not seem to result from the trained class of irrelevant attribute attracting more attention. Finally, Experiment 8 followed up an incidental observation in Experiment 1 to establish the novel observation that a task-switching context abolishes the usual ERP correlate of withholding a response in a go/no-go paradigm, suggesting an interesting interaction between task-set control and response inhibition.Economic and Social Research Council (ESRC

Stochastic inversion of linear first kind integral equations I. Continuous theory and the stochastic generalized inverse

The dataset associated with this paper is in ORE; see http://hdl.handle.net/10871/17644© 2015 American Psychological AssociationThis article may not exactly replicate the final version published in the APA journal. It is not the copy of record.This paper is made available in accordance with publisher policies. The final published version of this article is available from the publisher’s site. at http://www.apa.org/pubs/journals/xhp/index.aspxBefore reusing this item please check the rights under which it has been made available. Some items are restricted to non-commercial use. Please cite the published version where applicable.The present study explores the link between attentional reorienting and response inhibition. Recent behavioral and neuroscience work indicates that both might rely on similar cognitive and neural mechanisms. We tested two popular accounts of the overlap: The ‘circuit breaker’ account, which assumes that unexpected events produce global suppression of motor output, and the ‘stimulus detection’ account, which assumes that attention is reoriented to unexpected events. In Experiment 1, we presented standard and (unexpected) novel sounds in a go/no-go task. Consistent with the stimulus detection account, we found longer RTs on go trials and higher rates of commission errors on no-go trials when these were preceded by a novel sound compared with a standard sound. In Experiment 2, novel and standard sounds acted as no-go signals. In this experiment, the novel sounds produced an improvement on no-go trials. This further highlights the importance of stimulus detection for response inhibition. Combined, the two experiments support the idea that attention is oriented to novel or unexpected events, impairing no-go performance if these events are irrelevant but enhancing no-go performance when they are relevant. Our findings also indicate that the popular circuit breaker account of the overlap between response inhibition and attentional reorienting needs some revision.European Research CouncilFPU Fellowshi

Task switching without knowledge of the tasks.

CogSci 2012 - 34th annual meeting of the Cognitive Science Society, Sapporo, Japan, 1-4 August 2012Task-cuing paradigms are typically taken to explore control of task-set. However, they can be construed as requiring not selection of a task-set, just retrieval of a cue+stimulus-->response (CSR) mapping. In this paper we considered performance in a task-cuing paradigm in which participants saw a color cue that indicated whether they should classify a digit as odd/even or high/low using one of two responses. Half the participants were instructed in terms of tasks (Task group) whilst the others were required to learn the CSR mappings without mention of tasks (CSR group). Predicted performance under CSR conditions was modeled using an APECS connectionist network. Both the model and CSR group produced small switch costs, mostly due to incongruent stimuli, and large congruency effects that reduced with practice. In contrast, the Task group produced a larger switch-cost and a smaller, stable congruency effect

Processing differences across regular and irregular inflections revealed through ERPs

Research strongly suggests that printed words are recognized in terms of their constituent morphemes, but researchers have tended to consider the recognition of derivations and inflections in separate theoretical debates. Recently, Crepaldi et al. (2010) proposed a theory that claims to account for the recognition of both derivations and inflections. We investigated brain potentials in the context of masked priming to test two key predictions of this theory: (a) that regular inflections should prime their stems to a greater degree than irregular inflections should prime their stems; and (b) that priming for regular inflections should arise earlier in the recognition process than priming for irregular inflections. Significant masked priming effects were observed for both regular and irregular inflections, though these effects were greater for regular inflections. ERP data further suggested that masked priming effects for regular and irregular inflections had different time courses. Priming for regular but not irregular inflections emerged in a time window reflecting processing up to 250 ms post target onset, and while priming for regular and irregular inflections was observed in a time window reflecting processing 400-600 ms post target onset, these effects arose earlier and were of greater magnitude for the regular inflections. These findings support a form-then-meaning characterisation of the visual word processing system such as that proposed by Crepaldi et al. (2010) and raise challenges for alternative approache

Face recognition and brain potentials: Disruption of configural information reduces the face inversion effect

Copyright © 2012 Cognitive Science Society.The face inversion effect (FIE) refers to the decline in performance in recognizing faces that are inverted compared to the recognition of faces in their normal upright orientation (Yin, 1969). Event-related potentials (ERPs) were recorded while subjects performed an Old/New recognition study on normal and Thatcherised faces presented in upright and inverted orientation. A large difference in processing between normal upright faces and normal inverted faces was observed at occipital-temporal sites about 165 ms following stimulus onset, mainly in the right hemisphere. Thus electrophysiological activity, which corresponds to the previously described N170, had larger amplitude and was delayed for normal inverted faces as compared to normal upright ones. By contrast, the activity for Thatcherised inverted faces was not significantly changed or delayed as compared to Thatcherised upright stimuli. These results combine to show how the effect of face inversion on the N170 is reliably greater when the faces are normal rather than Thatcherised. Finally, these finding complement, at a neural level, our behavioral studies which suggest that the loss of some configural information affects the FIE

How task set and task switching modulate perceptual processes: Is recognition of facial emotion an exception?

Data Accessibility Statement: The data are available on the UK data service Reshare, http://doi.org/10.5255/UKDA-SN-855092This is the final version. Available on open access from Ubiquity Press via the DOI in this recordIn Part 1 we review task-switching and other studies showing that, even with time for preparation, participants’ ability to shift attention to a relevant attribute or object before the stimulus onset is limited: there is a ‘residual cost’. In particular, several brain potential markers of perceptual encoding are delayed on task-switch trials, compared to task-repeat trials that require attention to the same attribute as before. Such effects have been documented even for a process often considered ‘automatic’ – visual word recognition: ERP markers of word frequency and word/nonword status are (1) delayed when the word recognition task follows a judgement of a perceptual property compared to repeating the lexical task, and (2) strongly attenuated during the perceptual judgements. Thus, even lexical access seems influenced by the task/ attentional set. In Part 2, we report in detail a demonstration of what seems to be a special case, where task-set and a task switch have no such effect on perceptual encoding. Participants saw an outline letter superimposed on a face expressing neutral or negative emotion, and were auditorily cued to categorise the letter as vowel/consonant, or the face as emotional/neutral. ERPs exhibited a robust emotional-neutral difference (Emotional Expression Effect) no smaller or later when switching to the face task than when repeating it; in the first half of its time-course it did not vary with the task at all. The initial encoding of the valence of a fixated facial emotional expression appears to be involuntary and invariant, whatever the endogenous task/attentional set

Is preparing for a language switch like preparing for a task switch? (article)

This is the author accepted manuscript. The final version is available from APA via the DOI in this recordThe dataset associated with this article is located in ORE at https://doi.org/10.24378/exe.403There is another ORE record for this publication: http://hdl.handle.net/10871/36569A key index of top-down control in task switching-preparation for a switch-is underexplored in language switching. The well-documented EEG "signature" of preparation for a task switch-a protracted positive-polarity modulation over the posterior scalp-has thus far not been reported in language switching, and the interpretation of previously reported effects of preparation on language switching performance is complicated by confounding factors. In an experiment using event-related potentials (ERPs) and an optimized picture-naming paradigm that addressed these confounds the language was specified by an auditory cue on every trial and changed unpredictably. There were two key manipulations. First, the cue-stimulus interval allowed either generous (1,500 ms) or little (100 ms) opportunity for preparation. Second, to explore the interplay between bottom-up and top-down language selection, we compared a highly transparent and familiar "supercue"-the name of the language spoken in that language to a relatively opaque cue (short speeded-up fragment of national anthem). Preparation for a switch elicited a brain potential strongly reminiscent of the posterior switch positivity documented in task switching. As previously shown in task switching, its amplitude inversely predicted the performance "switch cost," demonstrated by our ERP analyses contingent on reaction time (RT). This overlap in the electrophysiological correlates of preparing to switch tasks and languages suggests domain-general processes for top-down selection of task-set and language for production. But, the surprisingly small language switch cost following the supercue in the short CSI suggests that rapid and (possibly automatic) bottom-up selection-not typically observed in task switching-may also occur. (PsycINFO Database RecordThe research described in this paper was supported by a PhD scholarship to the second author from the Economic and Social Research Council (ESRC, UK)

The face inversion effect and evoked brain potentials: Complete loss of configural information affects the N170

Copyright © 2012 Cognitive Science Society.The face inversion effect (FIE) is a reduction in recognition performance for inverted faces compared to upright faces that is greater than that typically observed with other stimulus types (e.g. houses; Yin, 1969). Nevertheless, the demonstration that the inversion effect in recognition memory can be as strong with images of dogs as with faces when the subjects are experts in specific dog breeds (Diamond & Carey, 1986), suggests that there may be other factors, such as expertise, which give rise to the FIE. Event-related potentials (ERPs) were recorded while subjects performed an Old/New recognition study on normal and scrambled faces presented in upright and inverted orientations. We obtained the standard result for normal faces: The electrophysiological activity corresponding to the N170 was larger and delayed for normal inverted faces as compared to normal upright ones. On the other hand, the ERPs for scrambled inverted faces were not significantly larger or delayed as compared to scrambled upright stimuli. These results, in combination, show how the effect of inversion on the N170 is reliably greater when the faces are normal compared to scrambled, which suggests the disruption of configural information affects the FIE.University of Exete

Perceptual learning and inversion effects: Recognition of prototype-defined familiar checkerboards.

PublishedJournal ArticleResearch Support, Non-U.S. Gov'tThe face inversion effect is a defection in performance in recognizing inverted faces compared with faces presented in their usual upright orientation typically believed to be specific for facial stimuli. McLaren (1997) was able to demonstrate that (a) an inversion effect could be obtained with exemplars drawn from a familiar category, such that upright exemplars were better discriminated than inverted exemplars; and (b) that the inversion effect required that the familiar category be prototype-defined. In this article, we replicate and extend these findings. We show that the inversion effect can be obtained in a standard old/new recognition memory paradigm, demonstrate that it is contingent on familiarization with a prototype-defined category, and establish that the effect is made up of two components. We confirm the advantage for upright exemplars drawn from a familiar, prototype-defined category, and show that there is a disadvantage for inverted exemplars drawn from this category relative to suitable controls. We also provide evidence that there is an N170 event-related potential signature for this effect. These results allow us to integrate a theory of perceptual learning originally proposed by McLaren, Kaye, and Mackintosh (1989) with explanations of the face inversion effect, first reported by Yin.University of ExeterNational Key Fundamental Research (973) Progra