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 str ength and relative timing on the magnitude of consistency effects for irrel evant information in Stroop-like tasks. Keypresses were made to two-dimensi onal 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, irrelev ant information affected performance regardless of whether its S-R associat ion was weak or strong, if the relevant S-R association was weak (e.g., col our 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 col our word persisted at a 500-ms SOA but that of an irrelevant physical colou r did not, reflecting different decay functions for irrelevant verbal and n on-verbal information. The persisting effect of an irrelevant colour word w as reduced by articulatory suppression and eliminated at extended SOAs of 3 s. The results indicate that whether the consistency effect patterns are s ymmetric or asymmetric is determined by the relative strengths of the relev ant and irrelevant S-R associations, as specified by the criteria of concep tual and mode similarity. The magnitude of the consistency effect is also a function of the temporal overlap of the resulting response activation, whi ch is determined primarily by mode similarity.