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Doctor of Philosophy




Lupker, Stephen J.


In the Stroop task, smaller congruency effects (i.e., the color-naming difference between incongruent items, e.g., the word RED in the color blue, and congruent items, e.g., RED in red) are found in conditions in which incongruent items are frequent vs. infrequent. Although the traditional explanation for these “Proportion-Congruent effects” is that attention to task-relevant information is more focused in frequently-conflicting conditions (a process involving adaptation to conflict frequency), Proportion-Congruent paradigms typically have not controlled for the impact of more general learning processes, particularly 1) learning of word-response contingencies (contingency learning), 2) learning about the predictive nature of the stimuli (stimulus informativeness), and 3) learning about response rhythm in the task (temporal learning), processes which could produce the Proportion-Congruent effects obtained in most situations. The present research examined the possibility that those non-conflict learning processes are indeed the whole story in Proportion-Congruent effects. Several different approaches were used. First, the proportion of congruent and incongruent items in a list was manipulated in a variant of the Stroop task in which no individual stimulus was repeated, creating a situation in which neither contingency learning nor stimulus informativeness could have influenced task performance. Second, manipulating the proportion of neutral (i.e., consonant strings) and incongruent items in a list allowed the creation of a parallel situation in the classic color-word Stroop task. A Proportion-Congruent effect and a similar, Proportion-Neutral effect, emerged in both tasks even though contingency learning and stimulus informativeness could have played no role in producing those effects. Further, attempts to examine the influence of temporal learning failed to show any evidence of that process contributing to those effects either. The final set of experiments involved a congruency-proportion manipulation specific to individual words within the same list. Contrary to the idea that the Proportion-Congruent effect obtained in this situation results from contingency learning, a concurrent working memory load impaired contingency learning in a non-conflict color identification task but spared the Proportion-Congruent effect in the Stroop task, favoring a conflict-adaptation interpretation of this effect. Overall, these results support the existence of a process of adaptation to conflict frequency in the human control system.

Summary for Lay Audience

This research was an examination of the processes that individuals use when dealing with distraction created by irrelevant but salient events (e.g., the type of situation created when a smartphone notification occurs while driving). The more specific focus was on the processes that individuals use when they can anticipate that a distracting event will occur. For example, it has normally been assumed that individuals can learn to increase attention to the current goal in situations in which distracting events are frequent. As a result of using this process of adaptation to distraction frequency, distraction becomes less disruptive in those situations than in situations in which distracting events are infrequent. Although many theories of how we deal with distraction assume that humans can and do use this process, recent research has suggested that the crucial experimental finding on which that assumption is based upon (i.e., that distraction is less disruptive in frequently distracting vs. infrequently distracting situations) actually results from more general learning processes for which the distracting vs. non-distracting nature of the event is irrelevant, e.g., people simply learn to produce the response that is typical for a certain event even when that event contains distracting information. In this research, I re-examined this conclusion by creating a series of experimental situations in which general learning processes were prevented from occurring, controlled for in the statistical analyses, or impaired by reducing the cognitive resources necessary to use them. In all of those situations, the crucial finding of reduced distraction in frequently distracting vs. infrequently distracting conditions emerged, suggesting that general learning processes are not the whole story in producing such findings. Instead, what these results suggest is that, consistent with most theorizing in this research area, humans possess and use the ability to adapt attention so as to deal with distraction more effectively when distracting events occur more frequently.

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.