Task interference from event-based intentions can be material specific

Task interference occurs in prospective memory tasks when an intention deleteriously affects performance on an ongoing activity in some way. Several studies have shown that task interference can manifest itself in slower latencies to perform an ongoing task. Recent evidence demonstrates that associating intentions to certain performance contexts affects prospective memory performance (see, e.g., Cook, Marsh, & Hicks, 2005). In the present study, an intention was associated with a particular stimulus class, such as pictures or words. We found that task interference could be reduced when participants could reliably predict that the material about to be processed was irrelevant to the intention. This material-specific interference effect was found on a trial-by-trial basis in a random sequence of two different kinds of materials across two experiments and with blocking manipulation in another experiment. These results demonstrate that task interference is not a monolithic construct; rather, it results from dynamic and flexible attentional allocation strategies that can change on a trial-by-trial basis.