Effects of task-irrelevant features over cognitive control processes
Final Report Abstract
Every object or person we encounter can be defined as a complex combination of colors, orientations, motion directions, sounds and smells. However, any purposeful behavior usually requires processing of only certain stimulus features: finding a car on a parking lot would primarily require analysis of shapes and colors. Not surprisingly, theories of cognitive control focused on the mechanisms that enable selective processing of task-relevant stimulus features. Importantly, some findings suggest that selective processing of task-relevant features is imperfect: under certain circumstances even task-irrelevant features may influence behavior. This project focused on describing conditions under which task-irrelevant features matter. The main hypothesis tested in this project was that task-irrelevant features will matter most when the target stimulus is difficult to differentiate from non-targets. Processing task-irrelevant features may help the differentiation between the target and non-targets and lead to measurable effects of task-irrelevant features on behavior. To test this hypothesis, this project made use of an interesting and counterintuitive empirical finding that adding more identical non-targets, e.g., yellow bars, actually makes the target, e.g., a red bar, easier to find. Across several experiments, the effects of task-irrelevant features were consistently stronger for displays with few non-targets relative to many non-targets. A computational model of response speed indicated that, to account for this behavioral result, it is necessary to assume that the target is more difficult to find when presented with a few non-targets. Electrophysiological recordings corroborated this finding. Further studies indicated that task-irrelevant features influence neural processes related to selecting the target amongst non-targets. Finally, computational modeling of response accuracy showed that task-relevant and taskirrelevant stimulus features are processed independently of each other. This project has shown that cognitive control is a flexible process – when the target and non-targets are easy to differentiate, only the task-relevant features are processed; when the differentiation is difficult, additional processes are recruited and task-irrelevant features matter. The results of this project offer a platform against which to evaluate further research on cognitive control. Finally, these findings can help identify situations under which people are most vulnerable to influences of task-irrelevant stimulus properties.
Publications
-
(2013). Visual search for feature singletons: Multiple mechanisms produce sequence effects in visual search. Journal of Vision, 13(3):22, 1-16
Rangelov, D., Müller, H. J., & Zehetleitner, M.
-
(2013). What are task-sets: A single, integrated representation or a collection of multiple control representations?, Frontiers in Human Neuroscience, 7:524
Rangelov, D., Töllner, T., Müller, H.J., & Zehetleitner, M.
-
(2014). Local feature suppression effect in face and non-face stimuli, Psychological Research, 1-12
Zinchenko, A., Kim, H., Danek, A., Müller, H.J., & Rangelov, D.
-
(2014). Non-binding relationship between visual features. Frontiers in Human Neuroscience, 8:749
Rangelov, D., & Zeki, S.
-
Failure to pop out: feature singletons do not capture attention under low signal-to-noise ratio conditions. Journal of Experimental Psychology: General, 146(5), 651-671, 2017
Rangelov, D., Müller, H.J., & Zehetleitner, M.
