Modeling panel detection frequencies by queuing system theory: an application in gas chromatography olfactometry

In continuous vigilance tasks, the number of coincident panel responses to stimuli provides an index of stimulus detectability. To determine whether this number is due to chance, panel noise levels have been approximated by the maximum coincidence level obtained in stimulus-free conditions. This study proposes an alternative method by which to assess noise levels, derived from queuing system theory (QST). Instead of critical coincidence levels, QST modeling estimates the duration of coinciding responses in the absence of stimuli. The proposed method has the advantage over previous approaches that it yields more reliable noise estimates and allows for statistical testing. The method was applied in an olfactory detection experiment using 16 panelists in stimulus-present and stimulus-free conditions. We propose that QST may be used as an alternative to signal detection theory for analyzing data from continuous vigilance tasks.     

Involvement and outcomes in short-term interpersonal cognitive problem solving groups

This study examined the extent to which patterns of involvement in interpersonal cognitive problem solving (ICPS) groups were predictive of improvements in ICPS skills. Thirty-one 7–8-year-old children were assigned to experimental or control groups. Participants in the experimental group participated in six sessions of ICPS group work. All participants were tested for the ICPS skills of alternative solutions thinking (AST) and consequential thinking (CT) immediately before and after the group work period. As predicted, the experimental group showed significantly greater improvements in AST and CT skills than the control group. Means-end thinking was significantly correlated with improvements in AST and CT, level of involvement and positive behaviour within the groups were predictive of improvements in AST but not CT. Findings indicated the importance of group dynamics for ICPS outcomes and are discussed in relation to their theoretical and practical implications.     

Water temperature determines neurochemical and behavioural responses to forced swim stress: an in vivo microdialysis and biotelemetry study in rats

Forced swimming is a behavioural stress model increasingly used to investigate the neurocircuitry of stress responses. Although forced swim stress clearly is a psychological stressor (anxiety, panic), its physical aspects are often neglected. There are indications that behavioural and neurochemical responses to swim stress depend on the water temperature. Thus, we investigated the responsiveness of hippocampal serotonergic neurotransmission (important in the coordination of stress responses), and of behaviour and core body temperature to forced swimming at different water temperatures (19, 25 and 35 degrees C). In vivo microdialysis and biotelemetry in freely-behaving rats were used. Dialysates were analysed for serotonin (5-HT) and its metabolite 5-HIAA (5-hydroxyindoleacetic acid) by HPLC with electrochemical detection. Forced swimming in water at 25 and 19 degrees C decreased core body temperature by 8 and 12 degrees C, respectively. A rapid and pronounced increase in hippocampal 5-HT and 5-HIAA was found in rats that swam at 35 degrees C, whereas biphasic responses in 5-HT and 5-HIAA were observed at 25 and 19 degrees C. Also swim stress behaviour and post-stress home cage behaviour depended on the water temperature. Comparing the serotonergic and core body temperature changes revealed that a combination of two different 5-HT and 5-HIAA responses seems to shape the neurotransmitter response. Swimming-induced increases in hippocampal extracellular concentrations of 5-HT and 5-HIAA occurred at all water temperatures, but these increases were temporarily quenched, or concentrations were transistently decreased, when core body temperature fell below 31 degrees C in water at 25 or 19 degrees C. These data demonstrate that water temperature is a key factor determining the impact of forced swim stress on behaviour and neurochemistry, and underscore that changes in these parameters should be interpreted in the light of the autonomic responses induced by this stressor.     

The role of orthography in speech production revisited

The language production system of literate adults comprises an orthographic system (used during written language production) and a phonological system (used during spoken language production). Recent psycholinguistic research has investigated possible influences of the orthographic system on the phonological system. This research has produced contrastive results, with some studies showing effects of orthography in the course of normal speech production while others failing to show such effects. In this article, we review the available evidence and consider possible explanations for the discrepancy. We then report two form-preparation experiments which aimed at testing for the effects of orthography in spoken word-production. Our results provide clear evidence that the orthographic properties of the words do not influence their spoken production in picture naming. We discuss this finding in relation to psycholinguistic and neuropsychological investigations of the relationship between written and spoken word-production.     

Memory of imagined actions: Imagining oneself or another person

Summary In two experiments, three modes of action encoding were compared: overt enactment, self-imagination, and imagination of another person performing the actions. Overt enactment and imagining self-performance of an action are mainly assumed to involve motor-kinesthetic representations, whereas imagining another person is thought to place more demands on the visual representational system. Previous paired-associate learning data on memory of action verbs showed that motor-kinesthetic imagery hinders pair integration, but that pair integration is facilitated by visual imagery. The comparison of free and cued recall of actions learned from lists of concrete nouns supports the assumption that the representational properties of overt enactment and self-imagination differ from those involved in the imagining of another person.     

Pair-relational encoding of performed nouns and verbs

Summary Subjects had to learn lists of noun pairs and verb pairs. They were informed in advance about the test types and were tested for free recall (FR) and cued recall (CR). Three classes of encoding instructions were used: standard learning instructions, item-specific enactment instructions (to perform the denoted action of the verb or a typical action for the noun, and to do the same plus finding separate goals for the two elements of each pair), and enactment instructions that were completed by explicit instructions to integrate the word pairs (find a common goal, and find a common goal plus rating your success). There was no effect of encoding instructions on FR of nouns. There was a better FR under all enactment instructions than under standard instructions for verbs. CR decreased after item-specific enactment instructions, in contrast with standard learning instructions, but more for nouns than for verbs. CR increased after the instructions to integrate the pairs, in contrast with item-specific enactment instructions, but more for nouns than for verbs. It was concluded that enactment provides excellent item-specific information that can hardly be enhanced further, and that the item-specific information provided by concrete nouns is fundamentally good and is difficult to enhance by enactment. It is further assumed that enactment not only provides excellent item-specific information, but also hinders pair integration. Therefore, CR decreases after enactment. This decrease can only be overcome when subjects actively try to integrate the word pairs.