title: The relationship between executive functions and fluid intelligence in schizophrenia.
abstract: An enduring question is unity vs. separability of executive deficits resulting from impaired frontal lobe function. In previous studies, we have asked how executive deficits link to a conventional measure of fluid intelligence, obtained either by standard tests of novel problem-solving, or by averaging performance in a battery of novel tasks. For some classical executive tasks, such as the Wisconsin Card Sorting Test (WCST), Verbal Fluency, and Trail Making Test B (TMTB), frontal deficits are entirely explained by fluid intelligence. However, on a second set of executive tasks, including tests of multitasking and decision making, deficits exceed those predicted by fluid intelligence loss. In this paper we discuss how these results shed light on the diverse clinical phenomenology observed in frontal dysfunction, and present new data on a group of 15 schizophrenic patients and 14 controls. Subjects were assessed with a range of executive tests and with a general cognitive battery used to derive a measure of fluid intelligence. Group performance was compared and fluid intelligence was introduced as a covariate. In line with our previous results, significant patient-control differences in classical executive tests were removed when fluid intelligence was introduced as a covariate. However, for tests of multitasking and decision making, deficits remained. We relate our findings to those of previous factor analytic studies describing a single principal component, which accounts for much of the variance of schizophrenic patients' cognitive performance. We propose that this general factor reflects low fluid intelligence capacity, which accounts for much but not all cognitive impairment in this patient group. Partialling out the general effects of fluid intelligence, we propose, may clarify the role of additional, more specific cognitive impairments in conditions such as schizophrenia.
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina ; Laboratory of Cognitive and Social Neuroscience (LaNCyS), UDP-INECO, Foundation Core on Neuroscience (UIFCoN), Diego Portales University Santiago, Chile ; Neuropsychology Department, Institute of Neurosciences Favaloro University Buenos Aires, Argentina.
authors.forename: María
authors.initials: M
authors.lastname: Roca
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina ; Neuropsychology Department, Institute of Neurosciences Favaloro University Buenos Aires, Argentina.
authors.forename: Facundo
authors.initials: F
authors.lastname: Manes
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina ; Neuropsychology Department, Institute of Neurosciences Favaloro University Buenos Aires, Argentina.
authors.forename: Marcelo
authors.initials: M
authors.lastname: Cetkovich
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina.
authors.forename: Diana
authors.initials: D
authors.lastname: Bruno
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina ; Laboratory of Cognitive and Social Neuroscience (LaNCyS), UDP-INECO, Foundation Core on Neuroscience (UIFCoN), Diego Portales University Santiago, Chile ; Universidad Autónoma del Caribe Barranquilla, Colombia.
authors.forename: Agustín
authors.initials: A
authors.lastname: Ibáñez
authors.affiliation: Neuropsychology Research Department, Institute of Cognitive Neurology (INECO) Buenos Aires, Argentina ; Neuropsychology Department, Institute of Neurosciences Favaloro University Buenos Aires, Argentina.
authors.forename: Teresa
authors.initials: T
authors.lastname: Torralva
authors.affiliation: MRC Cognition and Brain Sciences Unit Cambridge, UK ; Department of Experimental Psychology, University of Oxford Oxford, UK.
authors.forename: John
authors.initials: J
authors.lastname: Duncan
keywords: decision making; executive function; fluid intelligence; frontal lobe; multitasking; schizophrenia