title: A neuropsychological assessment of dual-task costs in closed-head injury patients using Cohen's effect size estimation method.
abstract: A test of whether patients suffering from a severe closed-head injury (CHI) were affected by disproportionate dual-task costs compared to those of healthy control participants was carried out through a direct comparison of CHI effects on dual-task (psychological refractory period, or PRP) performance and on single-task performance. In the dual-task condition of the present experiment, independent choice-responses were required to two sequential stimuli presented at a variable stimulus onset asynchrony (SOA). A significant delay of the reaction time (RT) to the second stimulus was reported by both CHI patients and controls at short (SOA) compared to long SOA, i.e., a PRP effect. The PRP effect was more pronounced for CHI patients than controls. In the single-task condition, a single choice-response was required to a stimulus presented in isolation. The RT produced by CHI patients in the single-task paradigm was longer than the RT produced by controls. CHI effects on dual-task performance and on single-task performance were compared following (1) their transformation into Cohen's ds, and (2) the application of a correction algorithm taking into account the different reliability of single-task and dual-task measures. The analysis of Cohen's ds revealed that CHI effects on performance were, if anything, smaller in the dual-task condition than in the single-task condition. The results imply that CHI patient's slower responding in single- and dual-task performance reflects a single common cause--slowing of the central processing.
authors.affiliation: Department of Developmental Psychology, University of Padova, Via Venezia 8, 35131, Padova, Italy. dar@unipd.it
authors.forename: Roberto
authors.initials: R
authors.lastname: Dell'Acqua
authors.forename: Paola
authors.initials: P
authors.lastname: Sessa
authors.forename: Harold
authors.initials: H
authors.lastname: Pashler
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention; D002755:Choice Behavior; D003118:Color Perception; D005260:Female; D007839:Functional Laterality; D016489:Head Injuries, Closed / Q000523:psychology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000706:statistics & numerical data*; D010364:Pattern Recognition, Visual; D010897:Pitch Discrimination; D011594:Psychometrics; D011597:Psychomotor Performance; D011930:Reaction Time; D012016:Reference Values; D012033:Refractory Period, Psychological; D014705:Verbal Behavior