An item/order trade-off explanation of word length and generation effects

The item-order hypothesis suggests that under certain conditions increased item processing can lead to deficits in order processing, and that this produces a dissociation in performance between item and order tasks. The generation effect is one such example. The word length effect is seen as another instance where this trade-off might be observed. The following experiments compare word length and generation effects under serial recall and single item recognition conditions. Short words are better recalled than long words on the serial recall task but long words were better recognised than short words. The results are consistent with the item-order approach and support a novel explanation for the word length effect.     

Typical dreams: stability and gender differences

Although the variability of dream content is large, typical dream themes that occur quite often and are reported by many people can be identified (e.g., being chased, falling, flying, failing an examination, being unable to find a toilet or restroom). The present study is an investigation of the stability of the rank order of the dream themes and of gender differences in the content of dreams. The authors administered A. L. Zadra and T. A. Nielsen's (1997) Typical Dream Questionnaire to 444 participants. The findings indicated that most of the 55 dream themes occurred at least once in most of the participants' lifetimes. In addition, the correlation coefficients for the rank order of the themes were very high; that is, the relative frequencies were stable. The gender differences in the present study were in line with content analytic findings; for example, men reported dreams about physical aggression more often than did women. Overall, previous research and the present data indicate that available research results of the measurement of typical dream themes are reliable and valid. The question of the meaning of these themes or the relationship between typical dream contents and waking life experiences, however, has not yet been answered and is open to future research.     

Motor adaptation to different dynamic environments is facilitated by indicative context stimuli

When humans are exposed to external forces while performing arm movements, they adapt by compensating for these novel forces. The basis of this learning process is thought to be a neural representation that models the relation between all forces acting upon the system and the kinematic effects they produce, called inverse dynamic model (IDM). The present study investigated whether and how the predictability of a given external force affects the selection of an appropriate motor response to compensate for such force. Adult human subjects (N=32) held a handle that could rotate around the elbow joint and learned to perform goal-directed forearm flexion movements, while an external velocity-dependent negative damping force was applied that assisted forearm movement. Subjects were randomly assigned to two groups. In the associative group, the applied damping force was always associated with a specific initial position. Thus, after initial learning, the force application became predictable. In the non-associative group, where the same movements were performed, the applied force was independent of the initial position, so that no association between force and location could be formed. We found that only the associative group significantly reduced target error when damping was present. That is, the location cue aided these subjects in generating dynamic responses in the appropriate limb. Our results indicate that motor adaptation to different dynamic environments can be facilitated by indicative stimuli.     

Distance cognition in virtual environmental space: Further investigations to clarify the route-angularity effect

Two experiments with 72 participants in total investigated the route-angularity effect. This effect is shown when a greater number of turns along a route increase the estimated length of this route. In this study it was shown that the route-angularity effect is likely to be a memory-based effect depending on task difficulty. The important factor seems to be how heavily memory is loaded during learning. The route-angularity effect even appears in intentional learning, when memory is loaded heavily. Under this learning condition participants know beforehand that they have to estimate distances. All experiments were conducted in a controlled virtual environment, which allows a reliable investigation of distance estimations in environmental space.     

Inferential bridging relations reveal distinct neural mechanisms: evidence from event-related brain potentials

This study investigates the online comprehension of Determiner Phrases (DPs) as a function of the given-new distinction in two-sentence texts in German and further focuses on DPs whose interpretation depends on inferential information (so-called 'bridging relations'). Previous reaction time studies report an advantage of given over new information. In the present study, this difference is reflected in distinct neural mechanisms: event-related potentials reveal that previously introduced (i.e., given) DPs elicit a reduced N400, while new DPs show an enhanced N400 followed by a P600. Crucially, inferentially bridged DPs, which are hypothesized to share properties with new and given information, first pattern with given DPs (showing an attenuated N400) and then with new DPs (showing an enhanced P600). The data demonstrate that salience relations between DPs and prior context ease DP integration and that additional cost arises from the establishment of independent reference. They further reveal that processing cost associated with the interpretation of bridged DPs results from the anaphoric complexity of introducing an independent referent.     

Decomposing retrieval and integration in memory for actions: a multinomial modeling approach

Typically, action phrases are recalled better if participants are asked to enact the phrases than if they are just asked to remember them. When investigating which processes constitute this enactment effect a difficulty is that observable effects in standard memory tests are ambiguous because such tests require several processes. In the present article, we introduce a multinomial model that decomposes observable memory performance into a retrieval parameter and a parameter concerning the item-specific processing and integration of an action phrase. These parameters are estimated from free recall and cued recall performance. The model fitted the data of two experiments designed to test it. Experiment 1 demonstrated the basic usefulness of the model by showing expected differences in the integration parameter in the absence of unexpected differences in the retrieval parameter. Experiment 2 extended the conditions under which the model is useful by showing expected differences in the retrieval parameter even in the presence of unexpected differences in the integration parameter. Together, these findings support our theoretical framework according to which enactment generally boosts integration of action phrases, but increases retrieval only for phrases with context cues.     

Spatial knowledge of children with spina bifida in a virtual large-scale space

The spatial knowledge of 18 children with spina bifida and 18 healthy control children (matched according to sex, age, and verbal IQ) was investigated in a computer-simulated environment. All children had to learn a route through a virtual floor system containing 18 landmarks. Controlling for cognitive abilities, the results revealed that children with spina bifida showed impaired route knowledge but not an impaired landmark knowledge. Thus the results suggest that children with spina bifida are not impaired in all large-scale abilities similarly. The impairments of the children with spina bifida are more accentuated in more behaviour based measurements, which indicates a relation to the reduced mobility of the children with spina bifida.     

The item-order hypothesis reconsidered: The role of order information in free recall

According to the item-order approach of free recall, in pure short lists the free recall of unrelated items is organized according to their order of presentation in the study list. The approach was applied in the present study to experimenter-performed tasks (EPTs) and subject-performed tasks (SPTs). It claims that EPTs provide better serial order information than SPTs. Consequently, free recall of EPTs should be more organized along the presentation order of the items than the free recall of SPTs. In three experiments, some specific aspects of this approach were studied. Firstly, it was demonstrated that serial retrieval is not strongly used spontaneously and that its use is overestimated in the literature because it is usually evoked by an order reconstruction test which follows free recall testing. Secondly, a serial retrieval strategy in free recall can be encouraged by explicit instructions. Finally, the present experiments showed that a serial output strategy alone does not allow one to predict performance in free recall. The implications of these findings for the item-order approach will be discussed.     

Design-effects in prospective and retrospective memory for actions

There is ample evidence that memory for action phrases such as "open the bottle" is better in subject-performed tasks (SPTs), i.e., if the participants perform the actions, than in verbal tasks (VTs), if they only read the phrases or listen to them. It is less clear whether also the sole intention to perform the actions later, i.e., a prospective memory task (PT), improves memory compared with VTs. Inconsistent findings have been reported for within-subjects and between-subjects designs. The present study attempts to clarify the situation. In three experiments, better recall for SPTs than for PTs and for PTs than for VTs were observed if mixed lists were used. If pure lists were used, there was a PT effect but no SPT over PT advantage. The findings were discussed from the perspective of item-specific and relational information.