title: Cost-benefit and distributional analyses of accessory stimuli.
abstract: Accessory stimuli (AS) are task-irrelevant events (typically an auditory tone) that speed reaction time (RT). With two conditions (AS-present, AS-absent) it is unclear whether AS-presence causes benefits or AS-absence causes costs, possibly due to the expectancy violations. The current study added a third condition where AS were absent in blocks and not expected (pure blocks); in other blocks, AS occurred with a probability of 0.5 (mixed blocks), allowing cost-benefit analysis comparing AS-absent RTs in pure and mixed blocks. Results demonstrated RTs were slower when AS were absent, regardless of whether the absence occurred in a mixed block or a pure block, suggesting AS do provide a benefit to RT. Additionally, AS-facilitation across the RT distribution was analysed using cumulative distribution frequencies  and ex-Gaussian parameter estimation. Both provided converging evidence that AS-facilitation increases towards the slower end of the RT distribution. The implications for the utility of AS paradigms are discussed.
authors.affiliation: School of Psychology, Keele University, Dorothy Hodgkin Building, Keele, Staffordshire, ST5 5BG, UK. j.a.grange@psy.keele.ac.uk
authors.forename: James A
authors.initials: JA
authors.lastname: Grange
authors.forename: Andrew
authors.initials: A
authors.lastname: Lody
authors.forename: Sophie
authors.initials: S
authors.lastname: Bratt
mesh_terms: D000161:Acoustic Stimulation; D000293:Adolescent; D001307:Auditory Perception / Q000502:physiology*; D003220:Conflict, Psychological; D005260:Female; D006801:Humans; D008297:Male; D011930:Reaction Time / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult