Latent structure in measures of associative, semantic, and thematic knowledge.

There has been much debate about the relation between knowledge for meaning (semantic memory) and knowledge for words in context (associative memory). Many measures of that knowledge exist, but do they all measure the same thing? In this study, scaling, clustering, and factor-analytic techniques were used to reveal the structure underlying 13 variables. Semantic similarity determined from lexicographic measures is shown to be separable from the associative strength determined from word association norms, and these semantic and associative measures are in turn separable from abstract representations derived from computational analyses of large bodies of text. The three-factor structure is at odds with traditional views of word knowledge. The expression of long-term knowledge about words and the concepts they represent may be better viewed in terms of associative, semantic, and thematic information.

A database of associative strengths from the strength-sampling model: a theory-based supplement to the Nelson, McEvoy, and Schreiber word association norms.

The strength-sampling model of free association (Nelson, McEvoy, & Dennis, 2000) claims that the probability of word association in free-association norms results from a sampling process. For a given cue word, each response word has an underlying distribution of strength values. In the free-association task, presentation of the cue word activates a random sample of strengths, one for each response. The highest strength wins, and its response is reported. In the present work, gradient descent was used to compute the theoretical mean strengths for each cue-response pair in the Nelson, McEvoy, and Schreiber (2004) norms. The resulting database may be downloaded from www.psychonomic.org/archive/.

Separating bias and sensitivity in judgments of associative memory.

Ratings of the degree of association between words are linearly related to normed associative strengths, but the intercept is high, and the slope is shallow (the judgments of associative memory [JAM] function). Two experiments included manipulations intended to decrease the intercept and increase the slope. Discrimination training on many pairs of words and constraining ratings to sum to a constant both reduced the intercept but failed to change the slope. The intercept of the JAM function appears to contain a bias component that can be manipulated independently of the slope, which reflects sensitivity to associative strengths.

Judgments of associative memory.

Judgments of associative memory (JAM) were indexed by ratings given to pairs of cue and response words. The normed probabilities, p(response|cue), were obtained from free association norms. The ratings were linearly related to the probabilities. The JAM functions were characterized by high intercepts ( approximately 50 on a 100 point scale) and shallow slopes (<0.5). The JAM function generalized across materials and method of rating. The function was not affected by expectancies or semantic similarity. Attempts to alter the function by making alternative responses more available were unsuccessful. A computer simulation model (MINERVA 2) exhibited the linear JAM function and successfully accounted for more complex phenomena (like the joint influence of forward and backward associative strengths on ratings). The shallow JAM slope appears to result from a fundamental lack of discrimination among associative strengths. The high intercept appears to result partly from an independent post-mnemonic source of bias producing over-estimation of association.

An efficient method for estimating semantic similarity based on feature overlap: reliability and validity of semantic feature ratings.

Two studies were conducted in which human participants rated pairs of words according to the perceived degree to which the words' referents shared semantic features. The participants found thetask intuitive, simple, and quick to complete. The ratings were reliable and valid. Interrater and interstudy correlations were high, and ratings were good predictors of known feature overlap values obtained from existing semantic feature norms.

Attentional capture triggers an attentional blink.

Two experiments examined the possibility that attention directed to a distractor during rapid serial visual presentation (RSVP) can produce an attentional blink (AB). A to-be-ignored distractor (D1) preceded a target word (T2) by a variable lag in RSVP streams of black false-font distractors. D1 was highlighted by color and was a word, a string of consonants, a string of digits, or a string of false-font characters. Recall of T2 was significantly suppressed at short D1-T2 lags (the AB) but only when D1 contained letters; the AB was completely absent when D1 was composed of digits or false-font characters. Thus, the AB can be triggered by a highlighted distractor if the distractor shares features with a target.

Semantic distance norms computed from an electronic dictionary (WordNet).

WordNet, an electronic dictionary (or lexical database), is a valuable resource for computational and cognitive scientists. Recent work on the computing of semantic distances among nodes (synsets) in WordNet has made it possible to build a large database of semantic distances for use in selecting word pairs for psychological research. The database now contains nearly 50,000 pairs of words that have values for semantic distance, associative strength, and similarity based on co-occurrence. Semantic distance was found to correlate weakly with these other measures but to correlate more strongly with another measure of semantic relatedness, featural similarity. Hierarchical clustering analysis suggested that the knowledge structure underlying semantic distance is similar in gross form to that underlying featural similarity. In experiments in which semantic similarity ratings were used, human participants were able to discriminate semantic distance. Thus, semantic distance as derived from WordNet appears distinct from other measures of word pair relatedness and is psychologically functional. This database may be downloaded from www.psychonomic.org/archive/.

Sources of interference in the attentional blink: target-distractor similarity revisited.

Observers monitored streams of words or letters (10 items/sec) for one or two targets. An attentional blink (AB) effect was observed in which identification of the first target temporarily impaired identification of the second target. Target identification was impaired when the distractors were composed of either letters or false-font characters (cf. Maki, Couture, Frigen, & Lien, 1997). An asymmetrical AB effect was observed with letters and mathematical symbols; the AB effect was largest for symbol targets and letter distractors. The characters used in these experiments were rated on their meaningfulness, familiarity, and other stimulus properties. The rating data showed that pixel density best accounted for the asymmetrical target-distractor similarity effects. Modulation of the AB effect by target-distractor similarity appears to result partly from low-level masking. But masking effects may be reduced by attentional capture by target features.

Multimedia comprehension skill predicts differential outcomes of web-based and lecture courses.

College students (134 women and 55 men) participated in introductory psychology courses that were offered largely online (on the World Wide Web) or in a lecture format. Student comprehension skills were inferred from their scores on a multimedia comprehension battery. The learning of content knowledge was affected interactively by comprehension skill level and course format. Differences between format increased with comprehension skill such that the Web-based course advantage became greater as comprehension skill increased. This same pattern was not seen when self-reports of comprehension ability were used as the predictor. Furthermore, comprehension skill did not predict course satisfaction. Generally, students of all skill levels preferred the lecture courses.