The contribution of meaning to the detection of task conflict

Abstract

The color-word Stroop task produces both information conflict (detection of the ink color vs. word meaning) and task conflict (respond to the ink color vs. read the word). In the present study we measured both reaction time and pupil dilation, and the neutral stimuli in our study were non-readable letter strings as well as meaningless non-readable stimuli (i.e., colored patches and abstract character strings). Our results showed slowest responses in the incongruent trials and fastest responses in the congruent trials. However, no differences were found between the investigated neutrals. In contrast, pupil dilation was largest in the incongruent trials and smallest in the neutral trials. Moreover, the more the neutral stimuli were meaningless, the less the pupil dilation that was observed. Our results suggest that non-word meaningless stimuli reduced task conflict (compared to all the investigated conditions). Neutral equivalence should be taken into consideration in Stroop and Stroop-like tasks.

Task and information conflicts in the numerical Stroop task

“…In addition, RTs were shorter in congruent than in neutral trials that were shorter than in incongruent trials. This dissociation between RT and pupil dilation has already been presented in previous Stroop pupillometry studies (Hershman et al, , 2021. Moreover, while RTs did not provide any evidence for the task conflict (i.e., no reverse facilitation), pupil dilation provided evidence for task conflict when the neutral condition did not include numerical information (experiment 1).…”

“…Namely, the use of neutral trials that contain digits (e.g., 2 & 2) would create task conflict similar to the congruent condition (e.g., 2 & 4) and thus would disable revealing the task conflict. Similar situations occur in the Stroop color-word task when one uses a word as a neutral stimulus (Hershman et al, , 2021. To examine this possibility, we carried out an experiment with digits as neutrals.…”

“…Pupils increase due to exposure to dark stimuli (Ellis, 1981), however, pupil dilation is also considered to be an index of mental effort in cognitive control tasks in general (Kahneman & Beatty, 1966;van der Wel & van Steenbergen, 2018) and in the Stroop color-word task in particular (Brown et al, 1999;Laeng et al, 2011;Siegle et al, 2004). Temporal analysis of the pupil dilation shows that the indications for task conflict, measured by the difference between different neutral and congruent conditions, appear relatively early, whereas the information conflict, indicated by the divergence of the curves of the incongruent and congruent conditions, starts later Hershman et al, , 2021. In particular, after about 500 ms post-stimulus onset, the pupils were larger for congruent than for neutral trials (i.e., reverse facilitation and task conflict), and about 1000 ms post-stimulus onset, the pupils were larger for incongruent than for congruent trials (the information conflict).…”

“…For example, if one focuses on congruency (with no importance for neutral trials) and defines the Stroop effect as the RT difference between congruent and incongruent trials, then information conflict and nothing else is central to one's conceptualization of the task and the potential of interference. Recently, Hershman et al (2021) suggested that meaningful or word-like stimuli activate different degrees of task conflict. The more word-like a stimulus is, the larger the potential for task conflict.…”

“…However, our Stroop color‐word studies suggest that these conditions induce task conflict because of the presentation of the digits (or the words). In contrast, color patches would produce no task conflict in the context of the numerical Stroop task, similar to the color‐word context (Hershman et al, 2021).…”