Biomedical subjects

Gert Storms

Publications and source records attributed to Gert Storms.

14 recordsLinked to original sources

PubMed2006

Age-of-acquisition differences in young and older adults affect latencies in lexical decision and semantic categorization.

An ongoing discussion about the role of age of acquisition (AoA) in word processing concerns the confound with word frequency. This study removed possible frequency confounds by comparing AoA and word familiarity differences in young (18-23 years) and older (52-56 years) adults. A first study investigated the differences in AoA and word familiarity ratings. The norms of AoA and familiarity were significantly different for young and older adults whereas these were previously considered equivalent [Morrison, C. M., Hirsh, K. W., Chappell, T., & Ellis, A. W. (2002). Age and age of acquisition: An evaluation of the cumulative frequency hypothesis. European Journal of Cognitive Psychology, 14, 435-459]. In the second study, AoA and familiarity effects were significantly different for the older and young adults in a lexical decision task. The third study replicated these findings in a semantic artifact/naturally occurring categorization experiment, thus providing further evidence for AoA-effects when word processing requires semantic mediation. Results from both studies were in line with the hypothesis that AoA effects on word processing cannot be accounted for by word frequency or other possible confounds.

Adolescent↗

PubMed2005

Category content and structure in schizophrenia: an evaluation using the instantiation principle.

In numerous studies, researchers have suggested anomalies in semantics in patients with schizophrenia. In this study, the authors addressed whether one such anomaly might reflect a difference in knowledge content or in the structure or organization of this information. Using a category member production task and a typicality rating task, the authors assessed knowledge content and found that patients' and control participants' knowledge about categories of foods and animals was very similar. In terms of structure, their findings from a mathematical model of category judgment (the instantiation model; E. Heit & L. W. Barsalou, 1996) revealed a similar category structure in patients and control participants. In conclusion, the authors suggest that the content and organization of categories in patients with schizophrenia is similar to that in healthy control participants.

Adult↗

PubMed2005

Does the order of head noun and modifier explain response times in conceptual combination?

We describe a speeded sensibility judgment experiment in which noun-noun combinations in the Indonesian language were used that parallels Gagné and Shoben's (1997) study of combinations in the English language. Like English, Indonesian is read from left to right and contains noun-noun combinations that are formed by juxtaposing the nouns. However, unlike in English, the order of the modifier and the head noun is reversed. This difference between English and Indonesian combinations allowed us to assess whether sensibility judgments of combinations are affected primarily by the left-right order of the nouns or by different functional roles of the nouns (i.e., modifier vs. head noun). As in Gagné and Shoben's study, the modifier's relation frequency contributed significantly to predicting sensibility judgment times in a regression analysis, but the head noun's relation frequency did not. We discuss the implications of this finding for models of conceptual combination.

Humans↗

PubMed2004

Normative data for the Boston Naming Test in native Dutch-speaking Belgian children and the relation with intelligence.

This paper reports the results of a normative study of the 60-item version of the Boston Naming Test (BNT) in a group of 371 native Dutch-speaking Flemish children between the ages of 6 and 12 years. Analysis of test results revealed that BNT performance was significantly affected by age and gender. The gathered norms were shown to be significantly lower than published norms for comparable North-American children. Error analysis disclosed remarkable similarities with data from elderly subjects, with verbal semantic paraphasias and 'don't know' responses occurring most frequently. Finally, BNT scores were shown to correlate strongly with general intelligence as measured with the Raven Progressive Matrices. The relation between both measures can be of help in the diagnosis of identification naming deficits and impaired word-retrieval capacities.

Belgium↗

PubMed2004

Assessing the informational value of parameter estimates in cognitive models.

Mathematical models of cognition often contain unknown parameters whose values are estimated from the data. A question that generally receives little attention is how informative such estimates are. In a maximum likelihood framework, standard errors provide a measure of informativeness. Here, a standard error is interpreted as the standard deviation of the distribution of parameter estimates over multiple samples. A drawback to this interpretation is that the assumptions that are required for the maximum likelihood framework are very difficult to test and are not always met. However, at least in the cognitive science community, it appears to be not well known that standard error calculation also yields interpretable intervals outside the typical maximum likelihood framework. We describe and motivate this procedure and, in combination with graphical methods, apply it to two recent models of categorization: ALCOVE (Kruschke, 1992) and the exemplar-based random walk model (Nosofsky & Palmeri, 1997). The applications reveal aspects of these models that were not hitherto known and bring a mix of bad and good news concerning estimation of these models.

Algorithms↗

PubMed2004

Dutch norm data for 13 semantic categories and 338 exemplars.

A data set is described that includes eight variables gathered for 13 common superordinate natural language categories and a representative set of 338 exemplars in Dutch. The category set contains 6 animal categories (reptiles, amphibians, mammals, birds, fish, and insects), 3 artifact categories (musical instruments, tools, and vehicles), 2 borderline artifact-natural-kind categories (vegetables and fruit), and 2 activity categories (sports and professions). In an exemplar and a feature generation task for the category nouns, frequency data were collected. For each of the 13 categories, a representative sample of 5-30 exemplars was selected. For all exemplars, feature generation frequencies, typicality ratings, pairwise similarity ratings, age-of-acquisition ratings, word frequencies, and word associations were gathered. Reliability estimates and some additional measures are presented. The full set of these norms is available in Excel format at the Psychonomic Society Web archive, www.psychonomic.org/archive/.

Humans↗

PubMed2004

Linear separability in superordinate natural language concepts.

Two experiments are reported in which linear separability was investigated in superordinate natural language concept pairs (e.g., toiletry-sewing gear). Representations of the exemplars of semantically related concept pairs were derived in two to five dimensions using multidimensional scaling (MDS) of similarities based on possession of the concept features. Next, category membership, obtained from an exemplar generation study (in Experiment 1) and from a forced-choice classification task (in Experiment 2) was predicted from the coordinates of the MDS representation using log linear analysis. The results showed that all natural kind concept pairs were perfectly linearly separable, whereas artifact concept pairs showed several violations. Clear linear separability of natural language concept pairs is in line with independent cue models. The violations in the artifact pairs, however, yield clear evidence against the independent cue models.

Adolescent↗

PubMed2004

Measures of similarity in models of categorization.

This paper concerns the use of similarities based on geometric distance in models of categorization. Two problematic implications of such similarities are outlined. First, in a comparison between two stimuli, geometric distance implies that matching features are not taken into account. Second, missing features are assumed not to exist. Only nonmatching features enter into calculations of similarity. A new model is constructed that is based on the ALCOVE model (Kruschke, 1992), but it uses a feature-matching similarity measure (see, e.g., Tversky, 1977) rather than a geometric one. It is an on-line model in the sense that both dimensions and exemplars are constructed during the categorization process. The model accounts better than ALCOVE does for data with missing features (Experiments 1 and 2) and at least as well as ALCOVE for a data set without missing features (Nosofsky, Kruschke, & McKinley, 1992). This suggests that, at least for some stimulus materials, similarity in categorization is more akin to a feature-matching procedure than to geometric distance calculation.

Distance Perception↗

PubMed2003

Scaling and clustering in the study of semantic disruptions in patients with schizophrenia: a re-evaluation.

Some recent studies of semantics in schizophrenia have employed multidimensional scaling and clustering techniques to analyse verbal fluency and triadic comparison data. The conclusions have been: (i) patients generate fewer words in fluency tasks and display more variable similarity groupings of words in triadic tasks, and (ii) this is due to deficits in semantics. We analysed data from both tasks. On the verbal fluency task, patients produced significantly fewer responses than controls. The results also showed little patient-specific inter-individual consistency. Similarly, for triadic comparison data, we did not find much patient-specific inter-individual consistency. When correlating patients' results at different measurement times with means of controls, the data of individual patients (at either of the two measurement times) were not predicted better from their data at the other measurement time than from controls. This latter finding suggests little patient-specific intra-individual consistency and, thus, pleads against idiosyncratic semantic deficits. Our findings do not refute the hypothesis that schizophrenia is associated with semantic disruptions. However, our results demonstrate that because of severe statistical restrictions and requirements associated with some scaling and clustering techniques, these methods may not be as useful in this enterprise as previously thought.

Cluster Analysis↗

PubMed2003

On the use of scaling and clustering in the study of semantic deficits.

In the past decade, several studies have used scaling and clustering techniques to document semantic storage deficits in patients with Alzheimer's disease and in schizophrenia. In this article the authors argued that many of the conclusions drawn from these studies are unjustified by the data. They reviewed the methodology used in these studies and presented data from simulation studies to further investigate the validity of their conclusions. The authors elaborate on the criteria needed to exclude alternative accounts of the data and present empirical data from patients with Alzheimer's disease and normal control participants to demonstrate that analyses of the patients' proximity data do not provide unambiguous evidence for a generalized semantic storage deficit.

Aged↗

PubMed2003

The instantiation principle re-evaluated.

Three experiments are presented in which different aspects concerning Heit and Barsalou's (1996) instantiation principle were investigated. Mean typicalities of subordinate categories within superordinates were predicted very accurately for all investigated concepts. Multiple instantiations were shown to yield somewhat better predictions than single instantiation. The instantiation principle also successfully predicted mean typicalities on a different level (i.e., in lower-level concepts). An alternative account of Heit and Barsalou's findings was also proven wrong. Finally, correspondence between empirically obtained and predicted standard deviations is argued to be dubious, because of several possible sources of bias in the observed and predicted values.

Adolescent↗

PubMed2003

Decision-bound theory and the influence of familiarity.

In this article, we derive a nonparametric prediction from decision-bound theory (DBT). The crucial aspect that is tested is whether or not familiarity of a stimulus affects response time in categorization. We show that, for our design, DBT, extended with some reasonable and testable assumptions, predicts no familiarity effect. Our prediction is nonparametric in that, rather than fit a specific instantiation of general DBT, we posit only some general assumptions of this theory and derive the prediction from these assumptions. It is found that familiarity did have a strong impact on response time for at least half of our participants. We suggest that DBT is in itself incomplete and should be extended to account for the full range of available data.

Adolescent↗

PubMed2003

A relevance theory of induction.

A framework theory, organized around the principle of relevance, is proposed for category-based reasoning. According to the relevance principle, people assume that premises are informative with respect to conclusions. This idea leads to the prediction that people will use causal scenarios and property reinforcement strategies in inductive reasoning. These predictions are contrasted with both existing models and normative logic. Judgments of argument strength were gathered in three different countries, and the results showed the importance of both causal scenarios and property reinforcement in category-based inferences. The relation between the relevance framework and existing models of category-based inductive reasoning is discussed in the light of these findings.

Adolescent↗

PubMed2002

Fruits and vegetables categorized: an application of the generalized context model.

In the study reported in this paper, we investigated the categorization of well-known and novel food items in the categories fruits and vegetables. Predictions based on Nosofsky's (1984,1986) generalized context model (GCM), on a multiplicative-similarity prototype model, and on an instantiation model as applied in Storms, De Boeck, and Ruts (2001) were compared. Despite suggestions in the literature that prototype models predict categorization from large categories better than exemplar models do, our results showed that the exemplar-based GCM yielded clearly better predictions than did a (multiplicative-similarity) prototype model.

Adult↗