Assessing Beliefs about 'Environmental Illness/Multiple Chemical Sensitivity'

Knowledge representation was used to characterize beliefs in patients with Environmental Illness/Multiple Chemical Sensitivity (EI/MCS). EI/MCS patients, allergy and asthma patients, doctors and controls made relatedness judgments on concepts relevant to EI/MCS. Associative networks showed that EI/MCS patients viewed these concepts differently from others. Multiple chemical exposure was central in EI/ MCS networks, with many links to every other concept, but was only peripherally connected in the other subject networks. Similarity comparisons to an EI/MCS prototype network discriminated EI/MCS patients from the other control populations, as did an index based on critical concept pairs. This approach shows promise for distinguishing patient groups using belief structure.

The salience of temporal cues in the developing structure of event knowledge

Two experiments used a novel method called Pathfinder to examine whether the salience of temporal cues embedded in event structure increases developmentally and whether people link event actions by simple adjacency relationships or embed them in an organized whole. A sequential format for eliciting knowledge was compared with a less structured format for dinner and bedtime events. Adults and their 8- and 10-year-old children demonstrated well-developed script organizations regardless of format, and organization improved across this age range. In Experiment 1, temporal cues were not a salient basis of comparison for 6-year-olds, but in Experiment 2 they could use temporal cues when instructed to do so. The results suggest that temporal salience increases between 6 and 10 years and that temporal knowledge of event actions is highly organized in this age range. Furthermore, children's event knowledge functions partly in the interaction between their developing event knowledge and the support provided by sequential constraints in the environment.

The basis of transfer in artificial grammar learning

In two experiments, we examined the extent to which knowledge of sequential dependencies and/or patterns of repeating elements is used during transfer in artificial grammar learning. According to one view of transfer, learners abstract the grammar's sequential dependencies and then learn a mapping to new vocabulary at test (Dienes, Altmann, & Gao, 1999). Elements that are repeated have no special status on this view, and so a logical prediction is that learners should transfer as well after exposure to a grammar without repetitions as after exposure to a grammar with them. On another view, repetition structure is the very basis of transfer (Brooks & Vokey, 1991; Mathews & Roussel, 1997). Learners were trained on grammars with or without repeating elements to test these competing views. Learners demonstrated considerable knowledge of sequential dependencies in their training vocabulary but did not use such knowledge to transfer to a new vocabulary. Transfer only occurred in the presence of repetition structure, demonstrating this to be the basis of transfer.

Meaning, memory structure, and mental processes

Although people experience little difficulty in recognizing printed words and comprehending sentences, they cannot do it instantaneously. Experimental psychologists have recently measured the speed of these mental processes by applying a reaction-time method. The method provides new data concerning the organization and retrieval of familiar semantic information in human memory. It has been found that close relations between the meanings of words help people to recognize and pronounce the words faster, especially when the words are hard to see because of visual distortions. Close relations between word meanings also facilitate the comprehension of some sentences, as indicated by how long a person takes to decide whether the sentences are true or false. The facilitation is not universal, however. When the relation between the meanings of two words must be analyzed carefully, their proximity may actually inhibit mental processing. These results, along with additional findings, support the hypothesis that human memory includes a semantic network that represents various categories of objects at distinct locations linked to specify their relations with each other. The memory structure probably influences a number of different mental processes that use it. One possible access route to the network is through a set of detectors designed to accumulate sensory information and signal the presence of particular words. There also appear to be processes for searching and comparing pieces of knowledge after a person finds the memory locations of designated categories. Further research using the reaction-time method may provide a more detailed inventory of what facts are retrieved directly from memory and what are computed from other stored information (36).

Lexical ambiguity, semantic context, and visual word recognition

Some alternative hypotheses about the recognition of ambiguous words are considered. According to the selective-access hypothesis, prior semantic context biases people to access one meaning of an ambiguous word rather than another in lexical memory during recognition. In contrast, the nonselectiveaccess hypothesis states that all meanings of the word are accessed regardless of the context. We tested certain versions of these hypotheses by having students decide whether selected strings of letters were English words. The stimuli included test sequnces of three words in which the second word had two distinct possible meanings, whereas the first and third words were related to these meanings in various ways. When the first and third words were related to the same meaning of the ambiguous second word (e.g., SAVE-BANK-MONEY), the reaction time to recognize the third word decreased. But when the first and third words were related to different meanings of the second word (e.g., RIVER-BANK-MONEY), the reaction time for the third word was not reliably different from a control sequence with unrelated words. These and other data favor the selective-access hypothesis. Selective access to lexical memory is discussed in relation to models of word recognition.