Deriving semantic structure from category fluency: Clustering techniques and their pitfalls
ForfatterVoorspoels, Wouter; Storms, Gert; Longenecker, Julia; Verheyen, Steven; Weinberger, Daniel R.; Elvevåg, Brita
Assessing verbal output in category fluency tasks provides a sensitive indicator of cortical dysfunction. The most common metrics are the overall number of words produced and the number of errors. Two main observations have been made about the structure of the output, first that there is a temporal component to it with words being generated in spurts, and second that the clustering pattern may reflect a search for meanings such that the ‘clustering’ is attributable to the activation of a specific semantic field in memory. A number of sophisticated approaches to examining the structure of this clustering have been developed, and a core theme is that the similarity relations between category members will reveal the mental semantic structure of the category underlying an individual's responses, which can then be visualized by a number of algorithms, such as MDS, hierarchical clustering, ADDTREE, ADCLUS or SVD. Such approaches have been applied to a variety of neurological and psychiatric populations, and the general conclusion has been that the clinical condition systematically distorts the semantic structure in the patients, as compared to the healthy controls. In the present paper we explore this approach to understanding semantic structure using category fluency data. On the basis of a large pool of patients with schizophrenia (n = 204) and healthy control participants (n = 204), we find that the methods are problematic and unreliable to the extent that it is not possible to conclude that any putative difference reflects a systematic difference between the semantic representations in patients and controls. Moreover, taking into account the unreliability of the methods, we find that the most probable conclusion to be made is that no difference in underlying semantic representation exists. The consequences of these findings to understanding semantic structure, and the use of category fluency data, in cortical dysfunction are discussed.
SiteringCortex (2013), online before print
Følgende lisensfil er knyttet til denne innførselen:
Viser innførsler relatert til tittel, forfatter og emneord.
Latent semantic variables are associated with formal thought disorder and adaptive behavior in older inpatients with schizophrenia Holshausen, Katherine; Harvey, Philip D.; Elvevåg, Brita; Foltz, Peter; Bowie, Christopher R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)Introduction: Formal thought disorder is a hallmark feature of schizophrenia in which disorganized thoughts manifest as disordered speech. A dysfunctional semantic system and a disruption in executive functioning have been proposed as possible mechanisms for formal thought disorder and verbal fluency impairment. Traditional rating scales and neuropsychological test scores might not be sensitive ...
Expectations of increased and decreased pain explain the effect of conditioned pain modulation in females Bjørkedal, Espen; Flaten, Magne Arve (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)Chronic pain is believed to be related to a dysfunction of descending pain modulatory mechanisms. Functioning of descending pain modulation can be assessed by various methods, including conditioned pain modulation (CPM). CPM refers to the inhibition of one source of pain by a second noxious stimulus, termed the conditioning stimulus. This procedure can activate an endogenous pain inhibitory mechanism ...
Invisible emotional expressions influence social judgments and pupillary responses of both depressed and non-depressed individuals. Laeng, Bruno; Sæther, Line; Holmlund, Terje; Wang, Catharina E.; Waterloo, Knut; Eisemann, Martin; Halvorsen, Marianne (Journal article; Tidsskriftartikkel; Peer reviewed, 2013)We used filtered low spatial frequency images of facial emotional expressions (angry, fearful, happy, sad, or neutral faces) that were blended with a high-frequency image of the same face but with a neutral facial expression, so as to obtain a “hybrid” face image that “masked” the subjective perception of its emotional expression. Participants were categorized in three groups of participants: healthy ...