A computational approach to modeling population differences

Age-Related Degree and Criteria Differences in Semantic Categorization

Individual differences in semantic categorization are commonplace. Individuals apply a word like SPORTS to different instances because they employ different conditions for category membership (vagueness in criteria) or because they differ regarding the extent to which they feel the term can be applied given fixed conditions (vagueness in degree). Three individuals may, for instance, disagree as to whether chess and hiking are SPORTS, because one believes SPORTS are competitive in nature, while the other two require SPORTS to be effortful (vagueness in criteria). On the basis of whether they consider hiking sufficiently effortful or not, the latter two individuals might still disagree as to whether to call it a SPORT (vagueness in degree). We investigated whether there are systematic age-related differences in semantic categorization by analyzing the categorization decisions of 1,868 adults for eight semantic categories with a formal model that allows the two sources of categorization differences to be disentangled. We found that young and older adults assess instances differently with respect to the categorization conditions and that older adults employ a lower threshold for category membership than young adults do. We recommend that these criteria and degree differences are taken into account in studies of age-related semantic processing.

The representation of ontological category concepts as affected by healthy aging: normative data and theoretical implications

Attributes associated with concept representations, such as familiarity, typicality, and age of acquisition, have been shown to be important influences on lexical-semantic processing. In most previous studies of healthy and pathological aging, these attributes are not equated for younger and older adults separately on the stimuli used. In this study, normative data were collected to test whether there exist any age differences in these attributes. The results demonstrate that the ratings given by younger and older adults on natural and manmade category items correlated positively. However, age differences were also apparent, whereby older adults provided higher ratings overall than younger adults. Suggestions and hypotheses are presented to explain this pattern of age differences, which relate to how category concepts may be represented by healthy younger and older adults. Also, the possible implications for these differential age ratings on lexical-semantic processing are discussed. The age differences apparent in this study demonstrate the need to consider age-appropriate normative ratings in the selection of stimuli for use in lexical-semantic processing studies of aging, and the normative data presented provide a means of equating category stimuli. The complete list of all the means is available at www.psychonomic.org/archive.