Individual differences in task-switching paradigms

Previous attempts to completely eliminate task-switch costs by improving advance preparation (e.g., Schneider, 2016, 2017) and by extensive practicing task rules (e.g., Zhao, Wang & Maes, 2018) had limited success; most researchers reported significant “residual” switch costs in typical task-switching paradigms, suggesting incomplete preparation of tasks. In most task-switching studies it was ignored that participants may have different switching abilities and/or strategies. It has been shown, however, that some participants perform better than others, showing only small switch costs for specific target-response mappings (Lindsen & De Jong, 2010), or reduced switch costs after extended practice of task rules (Stoet & Snyder, 2007). Other researchers have claimed that a few select participants showed superior performance in multi-tasking as well as other cognitive and perceptual tasks (Haaf & Rouder, 2017, 2018; Ramon et al., 2016; Robertson, Noyes, Dowsett, Jenkins & Burton, 2016; Strayer & Watson, 2012). It is therefore possible that in task-switching a few participants may also perform considerably better than others, showing minimal or no errors and no switch costs across different conditions. The present thesis aimed to study individual differences in task switching by monitoring group-average as well as individual performance under different conditions. Chapter 1 provides an overview of different task-switching paradigms and accounts to explain task-switch costs and residual switch costs. In particular, I discuss studies that considered individual differences in various tasks and experimental paradigms. In order to detect superior performance in task switching and to study individual differences, I conducted an experiment and two follow-up studies that are documented in Chapter 2. I employed Generalised Linear Mixed-effects Models (GLMMs; Bolker et al., 2009) on single-trial RTs in order to investigate whether individual participants exhibit comparable switching effects and whether best performers vary across different conditions, paradigms, and experiments. Seven psychological scales and a Raven intelligence test were also employed in order to better understand possible factors that may be related to differences in performance in task switching. The results of Chapter 2 suggest that there are considerable individual differences in task switching and that smaller individual switch costs may be due to more efficient preparation during cue-stimulus intervals. Furthermore, I suggest that efficient task preparation may be linked to better executive control, general intelligence, higher motivation, and lower levels of impulsivity. Since efficient preparation after task-cueing plays an important role in reducing or even eliminating switch costs, Chapter 3 sought to facilitate faster cue-based preparation, thereby reducing switch costs in typical participants. Previous research has suggested that task-switch costs are smaller for “transparent” compared to “non-transparent” or standard cues (e.g., Logan & Schneider, 2006; Schneider, 2016). In three experiments I compared “non-priming” cues with carefully designed “priming” cues that indicate the upcoming target feature and response mappings. I found that participants who used priming cues showed smaller and non-significant switch costs in their response times, independent of the interval between cue and target stimulus. These participants also showed more homogenous task-switching performance. In a related EEG study that investigated the temporal dynamics of preparation I provide evidence that priming cues elicited significantly larger cue-locked positivity in switch trials compared to repeat trials at electrode Pz, in different cue-stimulus intervals. Similar to previous results on transparent cues, this suggests that preparation can be facilitated (e.g., Karayanidis & Jamadar, 2014). Gender-related individual differences in task switching are investigated in Chapter 4. Previous reports on gender differences have been controversial (e.g., Polunina, Bryun, Sydniaeva & Golukhova, 2018; Stoet, O’Connor, Conner & Laws, 2013). In Chapter 4 I studied whether gender differences are present in the preparation phase of task-switching by manipulating the cue-stimulus interval. The results of the experiment in Chapter 4 suggest that females may have a slight advantage in task switching for longer preparation intervals. While individual switch costs varied considerably for female and male participants, females showed smaller congruency effects in trials with task repetition. I suggest that female participants were faster than males in task preparation. In addition, some females seemed to employ a different strategy in repeat trials. For example, they may have performed different tasks by recalling cue-stimulus-response associations without applying the task rules. In Chapter 5, I summarise possible reasons that may lead to superior switching performance and discuss other factors that may account for different switching performance across individuals. Limitations and future directions of research are also outlined. I suggest that individual differences should be considered and reported in order to improve model and hypothesis testing and to make results more replicable. Finally, I discuss whether superior switching abilities can be related to other tasks and situations

Exploring the Limitations of the Shielding Function of Categorization Rules in Task-Switching

Applying categorization rules narrows attention toward the relevant features of a target and helps participants to ignore the irrelevant features of the target. This is called the shielding function of categorization rules. Here we explored the limitation of the shielding function in two task-switching experiments. In Experiment 1, we assigned each target a single digital numeral as an additional feature in addition to conventional bivalent features as in the previous task-switching experiments with bivalent tasks. In the first two stages of Experiment 1, half of the participants learned the numeral-response associations and the other half used an alternative numeral-categorization rule to infer the response. Without participants applying conventional task-switching rules, the switching costs disappeared. Moreover, when participants performed tasks by numeral-response associations the bivalent features interfered with response retrieval and caused response-congruency effects, whereas when participants applied the numeral-categorization rule, the bivalent features were shielded away and thereby the response-congruency effects disappeared. In the third stage, in which all participants applied task-switching rules by discriminating between bivalent features (i.e., filling and orientations), we found task-switching costs and response-congruency effects. In Experiment 2, new bivalent features produced stronger interference compared to Experiment 1. As a consequence, participants in both the association group and the numeral-categorization rule group showed significant response-congruency effects in the first two stages, where task-switching rules were not introduced. It follows that the shielding function of categorization rules has limits—strong interference from bivalent features can break down the shielding function. In addition, participants in the association group showed task-switching costs without being informed about the task-switching rules. We propose that strong proactive interference can produce task-switching costs even without the use of task-switching rules

Task-switching costs disappear if non-Chinese participants respond to Chinese characters

In experiments with univalent target stimuli, task-switching costs can be eliminated if participants are unaware of the task rules and apply cue-target-response associations. However, in experiments with bivalent target stimuli, participants show task-switching costs. Participants may exhibit switch costs even when no task rules are provided in the instructions because they can infer the task rules. We tested this prediction by controlling the meaningfulness of cues and targets and therefore the ability to apply the task rules in 2 groups of participants. We compared the performance of Chinese and non-Chinese participants, who responded to Chinese numerals in an odd/even and high/low number task. In Experiment 1, Chinese participants, who knew Chinese characters and understood the task rules, showed task-switching costs. Non-Chinese participants on the other hand, who did not know Chinese characters, exhibited no switch costs. They applied a “target-first” strategy which means that they processed the target stimulus before the cue. In Experiment 2, we confirmed the absence of task-switching costs in Chinese participants using traditional Chinese numerals as target stimuli. Further, to determine how the target-first strategy affects switch costs, we manipulated the sequence of cue and target presentations. We conclude that task- switching costs can be eliminated more easily than previously thought, even for bivalent stimuli. The occurrence of task-switching costs depends on the approach used by participants and this may answer the puzzling question why humans typically do show task-switching costs whereas pigeons and monkeys do not

Advances in Single Nucleotide Polymorphisms of Vitamin D Metabolic Pathway Genes and Respiratory Diseases

Vitamin D is a fat-soluble vitamin. It is an essential vitamin for human body. It has a classical effect on regulating calcium and phosphorus metabolism. Participate in cellular and humoral immune processes by regulating the growth, differentiation and metabolism of immune cells. A large number of studies in recent years have shown that vitamin D deficiency increases the incidence of respiratory diseases. Respiratory diseases mainly include bronchial asthma, chronic obstructive pulmonary disease, tuberculosis, acute upper respiratory tract infection and pneumonia. Vitamin D metabolic pathway genes play a very important regulatory role in the transformation of vitamin D into active vitamin D, including CYP2R1,,CYP27B1, CYP24A1, VDBP, VDR five genes. Genetic polymorphism of genes is the molecular basis of individual differences and disease development. Therefore, this paper summarizes the research on single nucleotide polymorphism of vitamin D metabolic pathway gene and respiratory diseases. In order to provide a new idea for future treatment

Exploring individual differences in task switching

Previous research has shown that there are significant task-switching costs even when participants have time to prepare for task switching after cueing. We investigated individual differences in task switching by monitoring errors and response times of individual participants. In Experiment 1A, 58 participants were encouraged to finish the session early by completing 200 consecutive trials without making an error. In case of a mistake, they had to repeat their effort until the experimental session expired. Using this demanding procedure, 16 participants managed to complete early. Among these 16 we identified 9 best performers who showed no significant switch costs. We conducted follow-up Experiment 1B on these best performers by systematically varying cue-stimulus intervals and inter-trial intervals. The results confirmed that these participants had no significant RT and ER switch costs when they had time to prepare the task between cue and target onset. However, significant switch costs emerged when cue and target stimulus were presented simultaneously. In Experiment 1C, using three classical task-switching paradigms, we compared the best performers with 9 controls who had made frequent errors in Experiment 1A. Although the best performers responded faster and made fewer errors, they only showed reduced switch costs in a pre-cued paradigm that had been extensively practiced. In two other paradigms with simultaneous presentation of cue and target stimulus, best performers had switch costs and showed considerable individual differences similar to the controls. We conclude that there are considerable individual differences in task switching and that smaller individual switch costs are mainly related to efficient task preparation. We speculate that efficient task preparation may be linked to better executive control and general intelligence

Processing Speed Predicts Mean Performance in Task-Switching but Not Task-Switching Cost.

In several studies, it has been suggested that task-switching performance is linked to processing speed. Here we argue that the relation between processing speed and high-level cognitive ability found in previous studies may be due to confounded measurements of processing speed and task-switching ability. In the present study, we required participants to complete an inspection time (IT) task to probe their processing speed. We employed conventional task-switching paradigms but applied a linear integrated speed-accuracy score (LISAS) which combines latency and accuracy scores to express task-switching ability. The results of regression analyses show that IT predicted average performance in task-switching paradigms. However, IT did not relate to any specific effects common in the task-switching task, which contradicts previous results. Our results suggest independent mechanisms of processing speed and tasks that require a high level of cognitive flexibility and control

EREG is a risk factor for the prognosis of patients with cervical cancer

BackgroundCervical cancer continues to threaten women's health worldwide. Identifying critical oncogenic molecules is important to drug development and prognosis prediction for patients with cervical cancer. Recent studies have demonstrated that epiregulin (EREG) is upregulated in various cancer types, which contributes to cancer progression by triggering the EGFR signaling pathway. However, the role of EREG is still unclear.MethodsIn this study, we first conducted a comprehensive biological analysis to investigate the expression of EREG in cervical cancer. Then, we investigated the correlations between EREG expression level and clinicopathological features. In addition, we validated the effects of EREG expression on the proliferation and apoptosis of cervical cancer cells.ResultsBased on the public database, we found that the expression of EREG was higher in advanced cervical cancer samples. Survival analysis showed that EREG was a risk factor for the prognosis of cervical cancer. In vitro experiments demonstrated that EREG knockdown undermined proliferation and promoted apoptosis in cancer cells.ConclusionEREG plays a vital role in the progression of cervical cancer, which contributes to hyperactive cell proliferation and decreased cell apoptosis. It might be a valuable target for prognosis prediction and drug development for cervical cancer in the future