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In dieser Arbeit wird in mehreren Experimenten untersucht, wie gut junge und alte Erwachsene Sätze mit unterschiedlich komplexer syntaktischer Struktur verstehen können. Zentrales Thema dabei sind die Schwierigkeiten, die ältere Erwachsene mit der Objekt-vor-Subjekt-Wortstellung haben. Untersucht wird, inwiefern diese beobachteten Altersunterschiede durch eine reduzierte verbale Arbeitsgedächtniskapazität der älteren Erwachsenen erklärt werden können. Dabei stellt sich die Frage, ob die Defizite ein generelles verbales Arbeitsgedächtnis betreffen oder ob es ein eigenes Verarbeitungs-system für syntaktische Informationen gibt, dessen Kapazität mit dem Alter abnimmt. Es wurde versucht, die postulierte reduzierte Arbeitsgedächtniskapazität der älteren Erwachsenen an jungen Erwachsenen zu simulieren, indem deren Arbeitsgedächtniska-pazität durch eine Zusatzaufgabe künstlich eingeschränkt wurde. Weiterhin wurden die Altersunterschiede bei syntaktisch komplexen zentraleingebetteten Relativsätzen mit denen bei syntaktisch einfacheren koordinierten Hauptsätzen verglichen. Um die Studienteilnehmer mit den seltenen objektinitialen Strukturen zu konfrontieren und ihre Erfahrung mit solchen Sätzen zu verändern, wurden schließlich sowohl junge als auch alte Erwachsene mit Sätzen mit Objekt-vor-Subjekt-Wortstellung trainiert.
The limited capacity of working memory forces people to update its contents continuously. Two aspects of the updating process were investigated in the present experimental series. The first series concerned the question if it is possible to update several representations in parallel. Similar results were obtained for the updating of object features as well as for the updating of whole objects, participants were able to update representations in parallel. The second experimental series addressed the question if working memory representations which were replaced in an updating disappear directly or interfere with the new representations. Evidence for the existence of old representations was found under working memory conditions and under conditions exceeding working memory capacity. These results contradict the hypothesis that working memory contents are protected from proactive interference of long-term memory contents.
A mathematical model of working-memory capacity limits is proposed on the key assumption of mutual interference between items in working memory. Interference is assumed to arise from overwriting of features shared by these items. The model was fit to time-accuracy data of memory-updating tasks from four experiments using nonlinear mixed effect (NLME) models as a framework. The model gave a good account of the data from a numerical and a spatial task version. The performance pattern in a combination of numerical and spatial updating could be explained by variations in the interference parameter: assuming less feature overlap between contents from different domains than between contents from the same domain, the model can account for double dissociations of content domains in dual-task experiments. Experiment 3 extended this idea to similarity within the verbal domain. The decline of memory accuracy with increasing memory load was steeper with phonologically similar than with dissimilar material, although processing speed was faster for the similar material. The model captured the similarity effects with a higher estimated interference parameter for the similar than for the dissimilar condition. The results are difficult to explain with alternative models, in particular models incorporating time-based decay and models assuming limited resource pools.
During reading oculomotor processes guide the eyes over the text. The visual information recorded is accessed, evaluated and processed. Only by retrieving the meaning of a word from the long-term memory, as well as through the connection and storage of the information about each individual word, is it possible to access the semantic meaning of a sentence. Therefore memory, and here in particular working memory, plays a pivotal role in the basic processes of reading. The following dissertation investigates to what extent different demands on memory and memory capacity have an effect on eye movement behavior while reading. The frequently used paradigm of the reading span task, in which test subjects read and evaluate individual sentences, was used for the experimental review of the research questions. The results speak for the fact that working memory processes have a direct effect on various eye movement measurements. Thus a high working memory load, for example, reduced the perceptual span while reading. The lower the individual working memory capacity of the reader was, the stronger was the influence of the working memory load on the processing of the sentence.
Many comprehension theories assert that increasing the distance between elements participating in a linguistic relation (e.g., a verb and a noun phrase argument) increases the difficulty of establishing that relation during on-line comprehension. Such locality effects are expected to increase reading times and are thought to reveal properties and limitations of the short-term memory system that supports comprehension. Despite their theoretical importance and putative ubiquity, however, evidence for on-line locality effects is quite narrow linguistically and methodologically: It is restricted almost exclusively to self-paced reading of complex structures involving a particular class of syntactic relation. We present 4 experiments (2 self-paced reading and 2 eyetracking experiments) that demonstrate locality effects in the course of establishing subject-verb dependencies; locality effects are seen even in materials that can be read quickly and easily. These locality effects are observable in the earliest possible eye-movement measures and are of much shorter duration than previously reported effects. To account for the observed empirical patterns, we outline a processing model of the adaptive control of button pressing and eye movements. This model makes progress toward the goal of eliminating linking assumptions between memory constructs and empirical measures in favor of explicit theories of the coordinated control of motor responses and parsing.
Working memory load-dependent brain response predicts behavioral training gains in older adults
(2014)
In the domain of working memory (WM), a sigmoid-shaped relationship between WM load and brain activation patterns has been demonstrated in younger adults. It has been suggested that age-related alterations of this pattern are associated with changes in neural efficiency and capacity. At the same time, WM training studies have shown that some older adults are able to increase their WM performance through training. In this study, functional magnetic resonance imaging during an n-back WM task at different WM load levels was applied to compare blood oxygen level-dependent (BOLD) responses between younger and older participants and to predict gains in WM performance after a subsequent 12-session WM training procedure in older adults. We show that increased neural efficiency and capacity, as reflected by more "youth-like" brain response patterns in regions of interest of the frontoparietal WM network, were associated with better behavioral training outcome beyond the effects of age, sex, education, gray matter volume, and baseline WM performance. Furthermore, at low difficulty levels, decreases in BOLD response were found after WM training. Results indicate that both neural efficiency (i. e., decreased activation at comparable performance levels) and capacity (i. e., increasing activation with increasing WM load) of a WM-related network predict plasticity of the WM system, whereas WM training may specifically increase neural efficiency in older adults.
This dissertation investigates the working memory mechanism subserving human sentence processing and its relative contribution to processing difficulty as compared to syntactic prediction. Within the last decades, evidence for a content-addressable memory system underlying human cognition in general has accumulated (e.g., Anderson et al., 2004). In sentence processing research, it has been proposed that this general content-addressable architecture is also used for language processing (e.g., McElree, 2000).
Although there is a growing body of evidence from various kinds of linguistic dependencies that is consistent with a general content-addressable memory subserving sentence processing (e.g., McElree et al., 2003; VanDyke2006), the case of reflexive-antecedent dependencies has challenged this view. It has been proposed that in the processing of reflexive-antecedent dependencies, a syntactic-structure based memory access is used rather than cue-based retrieval within a content-addressable framework (e.g., Sturt, 2003).
Two eye-tracking experiments on Chinese reflexives were designed to tease apart accounts assuming a syntactic-structure based memory access mechanism from cue-based retrieval (implemented in ACT-R as proposed by Lewis and Vasishth (2005).
In both experiments, interference effects were observed from noun phrases which syntactically do not qualify as the reflexive's antecedent but match the animacy requirement the reflexive imposes on its antecedent. These results are interpreted as evidence against a purely syntactic-structure based memory access. However, the exact pattern of effects observed in the data is only partially compatible with the Lewis and Vasishth cue-based parsing model.
Therefore, an extension of the Lewis and Vasishth model is proposed. Two principles are added to the original model, namely 'cue confusion' and 'distractor prominence'.
Although interference effects are generally interpreted in favor of a content-addressable memory architecture, an alternative explanation for interference effects in reflexive processing has been proposed which, crucially, might reconcile interference effects with a structure-based account.
It has been argued that interference effects do not necessarily reflect cue-based retrieval interference in a content-addressable memory but might equally well be accounted for by interference effects which have already occurred at the moment of encoding the antecedent in memory (Dillon, 2011).
Three experiments (eye-tracking and self-paced reading) on German reflexives and Swedish possessives were designed to tease apart cue-based retrieval interference from encoding interference. The results of all three experiments suggest that there is no evidence that encoding interference affects the retrieval of a reflexive's antecedent.
Taken together, these findings suggest that the processing of reflexives can be explained with the same cue-based retrieval mechanism that has been invoked to explain syntactic dependency resolution in a range of other structures. This supports the view that the language processing system is located within a general cognitive architecture, with a general-purpose content-addressable working memory system operating on linguistic expressions.
Finally, two experiments (self-paced reading and eye-tracking) using Chinese relative clauses were conducted to determine the relative contribution to sentence processing difficulty of working-memory processes as compared to syntactic prediction during incremental parsing.
Chinese has the cross-linguistically rare property of being a language with subject-verb-object word order and pre-nominal relative clauses. This property leads to opposing predictions of expectation-based
accounts and memory-based accounts with respect to the relative processing difficulty of subject vs. object relatives.
Previous studies showed contradictory results, which has been attributed to different kinds local ambiguities confounding the materials (Lin and Bever, 2011). The two experiments presented are the first to compare Chinese relatives clauses in syntactically unambiguous contexts.
The results of both experiments were consistent with the predictions of the expectation-based account of sentence processing but not with the memory-based account. From these findings, I conclude that any theory of human sentence processing needs to take into account the power of predictive processes unfolding in the human mind.
This dissertation addresses the question of how linguistic structures can be represented in working memory. We propose a memory-based computational model that derives offline and online complexity profiles in terms of a top-down parser for minimalist grammars (Stabler, 2011). The complexity metric reflects the amount of time an item is stored in memory. The presented architecture links grammatical representations stored in memory directly to the cognitive behavior by deriving predictions about sentence processing difficulty.
Results from five different sentence comprehension experiments were used to evaluate the model's assumptions about memory limitations. The predictions of the complexity metric were compared to the locality (integration and storage) cost metric of Dependency Locality Theory (Gibson, 2000). Both metrics make comparable offline and online predictions for four of the five phenomena. The key difference between the two metrics is that the proposed complexity metric accounts for the structural complexity of intervening material. In contrast, DLT's integration cost metric considers the number of discourse referents, not the syntactic structural complexity.
We conclude that the syntactic analysis plays a significant role in memory requirements of parsing. An incremental top-down parser based on a grammar formalism easily computes offline and online complexity profiles, which can be used to derive predictions about sentence processing difficulty.
The interruption of learning processes by breaks filled with diverse activities is common in everyday life. We investigated the effects of active computer gaming and passive relaxation (rest and music) breaks on working memory performance. Young adults were exposed to breaks involving (i) eyes-open resting, (ii) listening to music and (iii) playing the video game “Angry Birds” before performing the n-back working memory task. Based on linear mixed-effects modeling, we found that playing the “Angry Birds” video game during a short learning break led to a decline in task performance over the course of the task as compared to eyes-open resting and listening to music, although overall task performance was not impaired. This effect was associated with high levels of daily mind wandering and low self-reported ability to concentrate. These findings indicate that video games can negatively affect working memory performance over time when played in between learning tasks. We suggest further investigation of these effects because of their relevance to everyday activity.
The interruption of learning processes by breaks filled with diverse activities is common in everyday life. We investigated the effects of active computer gaming and passive relaxation (rest and music) breaks on working memory performance. Young adults were exposed to breaks involving (i) eyes-open resting, (ii) listening to music and (iii) playing the video game “Angry Birds” before performing the n-back working memory task. Based on linear mixed-effects modeling, we found that playing the “Angry Birds” video game during a short learning break led to a decline in task performance over the course of the task as compared to eyes-open resting and listening to music, although overall task performance was not impaired. This effect was associated with high levels of daily mind wandering and low self-reported ability to concentrate. These findings indicate that video games can negatively affect working memory performance over time when played in between learning tasks. We suggest further investigation of these effects because of their relevance to everyday activity.