The specificity of prospective memory costs

A current issue in the field of prospective memory (i.e., memory for intentions) is the extent to which intentions interfere with ongoing activities. A question of interest is whether this interference is specific to stimuli that are relevant to the intention or whether interference is more general in its influence. Participants performed a lexical decision task (LDT) with an embedded prospective memory (PM) task in which they had to remember to press a computer key if a pre-specified target appeared (e.g., GIRL). Results demonstrated a consistent pattern of results. Increased reaction time costs were observed on trials where there was a match between PM targets and non-target ongoing stimuli. That is, when a prospective memory target was a word, then reaction time costs were observed on non-target word LDT trials and there were no costs on non-target nonword trials. Similarly, if a PM target was a nonword (e.g., UEBL) then costs were observed on non-target nonword LDT trials relative to non-target word trials. Evidence from three experiments suggests that task interference is specific to the type of stimulus (word or nonword) that is relevant to the intention. We refer to this finding as a Stimulus Specific Interference Effect (SSIE).