Influence of irrelevant information on human performance: effects of S-R association strength and relative timing

Six experiments examined effects of stimulus-response (S-R) association strength and relative timing on the magnitude of consistency effects for irrelevant information in Stroop-like tasks. Keypresses were made to two-dimensional stimuli (a colour or location word surrounded by a coloured rectangle or arrow), with the irrelevant information presented simultaneously with or prior to the relevant information. With simultaneous presentation, irrelevant information affected performance regardless of whether its S-R association was weak or strong, if the relevant S-R association was weak (e.g., colour word to keypress). However, a weak irrelevant S-R association (location word to keypress) had little effect when paired with a strong relevant S-R association (arrow direction to keypress), except when the stimulus onset asynchrony (SOA) between the irrelevant and relevant information was 300 ms. When the relevant information was colour, the effect of an irrelevant colour word persisted at a 500-ms SOA but that of an irrelevant physical colour did not, reflecting different decay functions for irrelevant verbal and non-verbal information. The persisting effect of an irrelevant colour word was reduced by articulatory suppression and eliminated at extended SOAs of 3 s. The results indicate that whether the consistency effect patterns are symmetric or asymmetric is determined by the relative strengths of the relevant and irrelevant S-R associations, as specified by the criteria of conceptual and mode similarity. The magnitude of the consistency effect is also a function of the temporal overlap of the resulting response activation, which is determined primarily by mode similarity.