Stroop-like interference in a match-to-sample task: Further evidence for semantic competition?

The Stroop-matching task as a tool to study the correspondence effect using images of graspable and non-graspable objects

The Stroop-matching task is a variation of the Stroop task in which participants have to compare a Stroop stimulus attribute (color or word) to a second stimulus. The Stroop-matching response conflict (SMRC) represents an interference related to the processes involved in selection/execution of manual responses. In the present study, we developed a variation of the Stroop-matching task in which the Stroop stimuli were matched to graspable objects (a cup) with intact or broken handles laterally oriented (Experiment 1) or to colored bars laterally presented (Experiment 2). It allowed testing the presence of the correspondence effect for lateralized handles and bars and its possible influence on SMRC. Two different intervals (100 and 800 ms) were also included to investigate time modulations in behavioral performance (reaction time and accuracy). Fifty-five volunteers participated in the study. In both experiments, significant SMRC was found, but no interaction occurred between SMRC and correspondence effect, supporting that the hypothesis of different and relatively independent psychological mechanisms is at the basis of each effect. Because significant facilitation for ipsilateral motor responses (correspondence effect) occurred for graspable objects but not for lateralized bars, the attentional shift/spatial-coding view was not able to completely explain our data, and therefore, the grasping affordance hypothesis remained as the most plausible explanation. The time course of facilitation observed in the first experiment and by others indicates the importance of further studies to better understand the time dynamic of facilitation/inhibition of motor responses induced by graspable objects.

Inhibitory mechanisms involved in Stroop-matching and stop-signal tasks and the role of impulsivity

Stroop-like and stop-signal tasks are commonly used to evaluate "inhibition", a multifaceted concept fundamental to better understanding of executive functions. Both tasks demand inhibitory processes for their execution; the first requires inhibition of an irrelevant attribute, while the second involves the inhibition of a prepotent motor response. Impulsivity and decision-making represent two other factors that could be associated to executive control and to inhibitory dyscontrol. In this study we developed a behavioral protocol combining the Stroop-matching (a variation of the classic Stroop task) and the stop-signal tasks to investigate possible interactions between the inhibitory mechanisms involved in both tasks. Moreover, we searched for associations between behavioral performance of healthy participants, and self-reported impulsivity and decision-making processes assessed by the BIS-11 scale and IGT, respectively. Our results showed that the primary-task reaction time in the Stroop-matching task influenced the ability to inhibit motor responses in the stop-signal task. Moreover, impulsiveness scores (but not decision-making) were associated to behavioral performance. Importantly, motor and attentional impulsiveness correlated differently to performance depending on the existence of stop-signal trials in the task. Our protocol revealed promising findings concerning the interaction between different inhibitory processes and their association with impulsivity levels.