Abstract
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.
Highlights
One of the major functions of human cognitive control is to guide our focus of attention to relevant information and, ideally, ignore any irrelevant information or interference
Two four-way ANOVAs with mixed effects were conducted on mean response times (RTs) and error rates (ERs) to compare different conditions
Consistent with the previous study (Li et al, 2019a), we found that bivalent features produced response-congruency effects even when participants do not know the bivalent features and related task rules yet
Summary
One of the major functions of human cognitive control is to guide our focus of attention to relevant information and, ideally, ignore any irrelevant information or interference. Dreisbach and Haider (2008) for the first time demonstrated the shielding function of the categorization rules in a task-switching paradigm with univalent targets. In their experiment, eight targets were German words in green or red. Dreisbach and Haider (2008) reported that participants who applied the target-response associations still processed the irrelevant color feature of the words, as was indicated by a significant interaction between Response repetition effect (response-repeat, response-switch) and Color switching effect (repeat, switch): When the response was repeated (trial n–1 and trial n had the same response), color switching delayed the responses, but when the response was switched, color switching facilitated the responses. For participants who applied the move/non-move categorization rule, this interaction was completely absent
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