Category inference as a function of correlational structure, category discriminability, and number of available cues

Two experiments investigated category inference when categories were composed of correlated or uncorrelated dimensions and the categories overlapped minimally or moderately. When the categories minimally overlapped, the dimensions were strongly correlated with the category label. Following a classification learning phase, subsequent transfer required the selection of either a category label or a feature when one, two, or three features were missing. Experiments 1 and 2 differed primarily in the number of learning blocks prior to transfer. In each experiment, the inference of the category label or category feature was influenced by both dimensional and category correlations, as well as their interaction. The number of cues available at test impacted performance more when the dimensional correlations were zero and category overlap was high. However, a minimal number of cues were sufficient to produce high levels of inference when the dimensions were highly correlated; additional cues had a positive but reduced impact, even when overlap was high. Subjects were generally more accurate in inferring the category label than a category feature regardless of dimensional correlation, category overlap, or number of cues available at test. Whether the category label functioned as a special feature or not was critically dependent upon these embedded correlations, with feature inference driven more strongly by dimensional correlations.     

the media's portrayal of urban and rural school violence: a preliminary analysis

Although the juvenile arrest rate has declined in the last few years, public awareness of juvenile crime has not diminished (Snyder 1996; Schiraldi 1998). The recent rash of rural school shootings has, in fact, heightened public awareness of juvenile crime and delinquent behavior. This research examines acts of school violence that have been committed by juveniles in three rural school districts and analyzes how the newspaper media present these acts relative to similar acts committed by juveniles in urban school settings. Our content analysis of the Wall Street Journal, Louisville Courier Journal, New York Times, St. Louis Post Dispatch, Los Angeles Times, and Washington Post reveals that these newspapers present school violence in these two settings very differently and that these differences are reflected in the way the political system reacts to such incidents.     

Long-term memory for pictures under conditions of thematically related foils

Memory for pictures was investigated under conditions of difficult foil discriminability and lengthy retention intervals. The foils preserved the theme of the studied stimulus, but differed in the number and quality of nonessential physical details. In each experiment, subjects viewed colored photographs, black-and-white photographs, elaborated line drawings, and unelaborated line drawings, followed by an old/new (Experiment 1) or a four-alternative forced-choice (Experiment 2) test given either immediately, 1 day, 1 week, or 4 weeks following study; Experiment 3 replicated Experiment 1 but with a 12-week delay. For the old/new procedure, performance was best on colored photographs, with performance differences among the four stimulus types still significant after 4 weeks. For the forced-choice test, performance on colored photographs and unelaborated line drawings was best, with performance differences among stimulus types also still significant after 4 weeks. A confusion analysis indicated that errors were based on physical similarity, even after 12 weeks. These results refute the hypothesis that the memorial representations for pictorial variations converge to a common, thematic code after lengthy delays; instead, non-thematic, analogue information is encoded and preserved for lengthy time periods.     

Influence of manipulated category knowledge on prototype classification and recognition

The recognition and classification of category members was explored, following a variable number of learning trials. In Experiment 1, subjects received 1 or 9 learning trials, followed by a recognition-then-classification test containing old, new, prototype, and foil patterns. In Experiment 2, subjects received 1, 6, or 12 trials, and made either classification or recognition judgments. In each experiment, classification accuracy for all item types was at near-chance -performance after a single trial but steadily increased with increased learning trials. On the transfer test, oldness judgments were highest for the category prototype after a single trial. However, with increased learning trials, oldness judgments increased for old instances and decreased for the category prototype and new instances. We suggest that false recognition of the category prototype, especially after a single learning trial, need not reflect an abstraction process. We discuss the possibility that an abstracted prototype may emerge with additional learning as an unfamiliar, ideal point.     

Delayed memory for visual—haptic exploration of familiar objects

Long-term memory of haptic, visual, and cross-modality information was investigated. In Experiment 1, subjects briefly explored 40 commonplace objects visually or haptically and then received a recognition test with categorically similar foils in the same or the alternative modality both immediately and after 1 week. Recognition was best for visual input and test, with haptic memory still apparent after a week's delay. Recognition was poorest in the cross-modality conditions, with performance on the haptic-visual and visual-haptic cross-modal conditions being nearly identical. Visual and haptic information decayed at similar rates across a week delay. In Experiment 2, subjects simultaneously viewed and handled the same objects, and transfer was tested in a successive cue-modality paradigm. Performance with the visual modality again exceeded that with the haptic modality. Furthermore, initial errors on the haptic test were often corrected when followed by the visual presentation, both immediately and after 1 week. However, visual test errors were corrected by haptic cuing on the immediate test only. These results are discussed in terms of shared information between the haptic and visual modalities, and the ease of transfer between these modalities immediately and after a substantial delay.     

The modulating influence of category size on the classification of exception patterns

Generalization gradients to exception patterns and the category prototype were investigated in two experiments. In Experiment 1, participants first learned categories of large size that contained a single exception pattern, followed by a transfer test containing new instances that had a manipulated similarity relationship to the exception or a nonexception training pattern as well as distortions of the prototype. The results demonstrated transfer gradients tracked the prototype category rather than the feedback category of the exception category. In Experiment 2, transfer performance was investigated for categories varying in size (5, 10, 20), partially crossed with the number of exception patterns (1, 2, 4). Here, the generalization gradients tracked the feedback category of the training instance when category size was small but tracked the prototype category when category size was large. The benefits of increased category size still emerged, even with proportionality of exception patterns held constant. These, and other outcomes, were consistent with a mixed model of classification, in which exemplar influences were dominant with small-sized categories and/or high error rates, and prototype influences were dominant with larger sized categories.