Cognitive load in hypertext reading: A review

A process model of hypertext reading was used to generate predictions about the effects of hypertext features on cognitive processing during text navigation and comprehension. We evaluated the predictions of the model with respect to the extant literature, focusing on studies in which versions of hypertexts were compared. Consistent with our predictions, the increased demands of decision-making and visual processing in hypertext impaired reading performance. Individual differences in readers, such as working memory capacity and prior knowledge, mediated the impact of hypertext features. For example, readers with low working memory and low prior knowledge were usually disadvantaged in hypertext. Some benefits were observed for learners with low prior knowledge, however, if the hypertext structure was hierarchical and consistent with that of the knowledge domain. We also surveyed the effectiveness of structural features designed to reduce cognitive load, including graphical overviews, restricted access to links, and visible link types. Complex graphical overviews did not reliably enable learning and navigation, whereas navigational support from restricted access and visible link types were helpful. We identified gaps in the empirical literature and suggested future studies to investigate cognitive processes in hypertext reading.     

Reading skills and children’s navigation strategies in hypertext

Prior research has identified two important navigation strategies that have a clear impact on hypertext comprehension: link selection and overview processing strategies. The first relate to the order in which students select hyperlinks while trying to comprehend a hypertext, whereas the second relate to when and for how long students process navigation overviews, a text device that conveys the text structure by displaying sections, titles and their relations. Most prior research in navigation strategies has been conducted with undergraduate students. We extend prior research by exploring the navigation strategies used by sixth-graders while reading a hypermedia system. We also investigate how reading skills relate to the use of navigation strategies, and how both shape students’ comprehension in hypertext. Results from an electronic reading study replicated in sixth-graders the results on navigation strategies previously found in undergraduate samples. In addition, the results revealed that reading skills predicted the use of link selection but not of overview processing strategies. We discuss our results in light of new models of electronic reading proficiency, and propose some instructional guidelines to improve children’ electronic reading proficiency.     

Do graphical overviews facilitate or hinder comprehension in hypertext?

Educational hypertexts usually include graphical overviews, conveying the structure of the text schematically with the aim of fostering comprehension. Despite the claims about their relevance, there is currently no consensus on the impact that hypertext overviews have on the reader’s comprehension. In the present paper we have explored how hypertext overviews might affect comprehension with regard to (a) the time at which students read the overview and (b) the hypertext difficulty. The results from two eye-tracking studies revealed that reading a graphical overview at the beginning of the hypertext is related to an improvement in the participant’s comprehension of quite difficult hypertexts, whereas reading an overview at the end of the hypertext is linked to a decrease in the student’s comprehension of easier hypertexts. These findings are interpreted in light of the Assimilation Theory and the Active Processing model. Finally, the key educational and hypertext design implications of the results are discussed.     

Is single or dual channel with different English proficiencies better for English listening comprehension,cognitive load and attitude in ubiquitous learning environment?

The purpose of the present study was to examine the effects of English proficiency (low vs. high) and material presentation mode (single channel vs. dual channel) on English listening comprehension, cognitive load and learning attitude in a ubiquitous learning environment. An experimental learning activity was implemented using PDA as a learning tool to facilitate learning. A quasi-experimental design was employed with university students participating in the experiment. The results revealed that (a) high English proficiency learners had significantly better English listening comprehension and lower intrinsic and extraneous load than low English proficiency learners; (b) both high and low English proficiency learners learning with dual channel had significantly better English listening comprehension and held more positive attitude toward the ubiquitous learning environment than learners learning with single channel; (c) for learners learning with single channel, low English proficiency learners had significantly higher extraneous load than high English proficiency learners; and (d) for low English proficiency learners, learners who learned with dual channel possessed significantly lower extraneous load than learners who learned with single channel. The suggestions for educators and instructional designers were also discussed in the present study.     

Do graphical overviews facilitate or hinder comprehension in hypertext?

Educational hypertexts usually include graphical overviews, conveying the structure of the text schematically with the aim of fostering comprehension. Despite the claims about their relevance, there is currently no consensus on the impact that hypertext overviews have on the reader’s comprehension. In the present paper we have explored how hypertext overviews might affect comprehension with regard to (a) the time at which students read the overview and (b) the hypertext difficulty. The results from two eye-tracking studies revealed that reading a graphical overview at the beginning of the hypertext is related to an improvement in the participant’s comprehension of quite difficult hypertexts, whereas reading an overview at the end of the hypertext is linked to a decrease in the student’s comprehension of easier hypertexts. These findings are interpreted in light of the Assimilation Theory and the Active Processing model. Finally, the key educational and hypertext design implications of the results are discussed.     

The influence of text modality on learning with static and dynamic visualizations

In this study we investigated the influence of text modality on learning with static and dynamic visualizations in a dynamic domain, namely the physical principles underlying fish locomotion. A 2 × 2-design with type of visualization (static vs. dynamic) and text modality (spoken vs. written) as independent variables was used. Concerning learning outcomes, it was hypothesized that (1) learners presented with dynamic visualizations would outperform learners presented with static visualizations, (2) learners presented with spoken text would outperform learners presented with written text, and (3) an interaction between type of visualization and modality would occur: the superiority of dynamic over static visualizations was expected to be more pronounced for spoken compared to written text. Subjective cognitive load measures were assessed and expected to mirror the aforementioned pattern of learning outcomes in accordance with Cognitive Load Theory (i.e., higher extraneous cognitive load (ECL) related to lower learning outcomes). For transfer tasks, the first two hypotheses could be confirmed. However, there was no interaction. Moreover, ECL was rated higher by subjects when learning with static compared to dynamic visualizations, but there were no differences for ECL with respect to the text modality. The results are discussed within the framework of Cognitive Load Theory.     

How hypertext fosters children’s knowledge acquisition: The roles of text structure and graphical overview

Children in primary and secondary school are asked to go on the Internet for school purposes while research on hypertext has scarcely investigated how children process and learn from hypertext. We therefore examined how hypertext influences children’s knowledge acquisition from expository text. A group of 71 Dutch children (13 years old) from one secondary school for pre-university education participated in the study. In a within-subjects design with four conditions, we compared: regular linear text, regular text with overview, hypertext, and hypertext with overview. Children’s (a) navigation (i.e., reading time and navigation pattern) and (b) learning (i.e., multiple choice knowledge questions and mind maps) was measured. Although reading times did not differ, the children navigated less linearly in both hypertext conditions than in the regular text with overview condition. The four types of text led to the same deep understanding as measured on the text base level. Analyses of the mind maps, however, showed the children to construct richer situation models after reading hypertext or hypertext with an overview relative to regular linear text and regular text with overview. We therefore conclude that hypertext fosters a deeper level of information processing when appropriately designed relative to regular linear text.     

The effects of the number of links and navigation support on cognitive load and learning with hypertext: The mediating role of reading order

Problems in learning with hypertext systems have been claimed to be caused by high levels of disorientation and cognitive load. This was recognized by DeStefano and LeFevre [DeStefano, D., & LeFevre, J. -A., (2007). Cognitive load in hypertext reading: A review. Computers in Human Behavior, 23(3), 1616–1641.] who predicted an increase of cognitive load and impairment of learning for hypertexts with a higher number of links per page. From a practical perspective, several navigation support techniques, such as providing link suggestions, have been proposed for guiding learners and reducing cognitive overload. In an experiment, we tested DeStefano and LeFevre’s predictions as well as the usefulness of link suggestions. Participants used different versions of a hypertext, either with 3-links or 8-links per page, presenting link suggestions or not. We tested their cognitive load and learning outcomes. Results showed that there was a benefit of using link suggestions for learning, but no effect of number of links on learning was found. Moreover, the effects of our manipulations on cognitive load were mediated by the reading order that participants selected. Implications for research and the design of navigation support systems are discussed.     

Just-in-time,schematic supportive information presentation during cognitive skill acquisition

Cognitive load theory states that well-designed learning material minimizes extraneous cognitive load and optimizes germane cognitive load within the thresholds of available cognitive resources. In this study, the extraneous cognitive load is minimized by avoiding temporal split attention with regard to supportive information (i.e., conceptual models or ‘theory’) and the germane cognitive load is optimized by using schematic representations of this information to direct learner’s attention to concepts relevant for learning. A 2 × 2 between-groups design with the factors supportive information (before or during practice) and schematic representation (before or during practice) was used to investigate whether this balance between extraneous and germane load leads to more effective and efficient learning. It was found that the ‘supportive during, schema before’ format indeed yielded a higher learning efficiency than the ‘supportive before, schema before’ and the supportive during, schema during’ format but no differences were found for learning effectiveness (i.e., test performance).     

The attention-guiding effect and cognitive load in the comprehension of animations

To be effective, instructional animations should avoid causing high extraneous cognitive load imposed by the high attentional requirements of selecting and processing relevant elements. In accordance with the attention-guiding principle (Bétrancourt, 2005), a study was carried out concerning the impact of cueing on cognitive load and comprehension of animations which depicted a dynamic process in a neurobiology domain. Cueing consisted of zooming in important information at each step of the process. Thirty-six undergraduate psychology students were exposed to an animation three times. Half of the participants received an animation without cueing while the other half received the same animation with cueing. Measures of cognitive load and comprehension performance (questions on isolated elements and on high-element interactivity material) were administered twice, after one and three exposures to the animation. The analyses revealed two main results. First, extraneous cognitive load was reduced by cueing after three exposures. Second, retention of the isolated elements was improved in both animation groups, whereas comprehension of high-element interactive material (i.e., the causal relations between elements) increased only in the cueing condition. Furthermore, a problem solving task showed that cueing supported the development of a more elaborate mental model.     

Comprehension and navigation of networked hypertexts

This study aims to investigate secondary school students' reading comprehension and navigation of networked hypertexts with and without a graphic overview compared to linear digital texts. Additionally, it was studied whether prior knowledge, vocabulary, verbal, and visual working memory moderated the relation between text design and comprehension. Therefore, 80 first‐year secondary school students read both a linear text and a networked hypertext with and without a graphical overview. Logfiles registered their navigation. After reading the text, students answered textbased multiple choice questions and drew mindmaps to assess their structural knowledge of each text content. It was found that both textbased and structural knowledge were lower after reading a networked hypertext than a linear text, especially in students with lower levels of vocabulary. Students took generally more time to read the hypertext than the linear text. We concluded that networked hypertexts are more challenging to read than linear texts and that students may benefit from explicit training on how to read hypertexts.     

What comes with technological convenience? Exploring the behaviors and performances of learning with computer-mediated dictionaries

As technology develops, the prevalence of conventional book dictionaries has slowly declined due to advancements in computer-mediated aids, such as online type-in dictionaries and program-installed pop-up aids. The goal of this study was to examine how technology “may” have changed the long-standing pedagogical practice of book dictionary usage by identifying the learning processes associated with various dictionaries and verifying how these processes are related to learning. Cognitive load theory was applied to generate predictions about learning performance and, therefore, to determine the nature of these processes. Information contained in each dictionary was specifically controlled, and thus we focused on the effect of the learning process alone. In the experiment, students first read a simulated online text in one of four conditions: pop-up, type-in, book dictionaries or no aid. They were later tested for reading comprehension and vocabulary learning. Results indicated that all dictionaries enhanced vocabulary learning but not comprehension. Close examination revealed that vocabulary-learning efficiency was significantly higher for the pop-up dictionary than the other two aids. In addition, a complex relationship existed between reading comprehension and vocabulary learning. This study has important implications for future dictionary design and pedagogical advice regarding dictionary usage.     

The influence of leads on cognitive load and learning in a hypertext environment

The purpose of this study was to determine the effect of leads (or hypertext node previews) on cognitive load and learning. Leads provided a brief summary of information in the linked node, which helped orient the reader to the linked information. Dependent variables included measures of cognitive load: self-report of mental effort, reading time, and event-related desynchronization percentage of alpha, beta and theta brain wave rhythms; and learning performance: a recall task, and tests of domain and structural knowledge. Results indicated that use of leads reduced brain wave activity that may reflect split attention and extraneous cognitive load, and improved domain and structural knowledge acquisition. Further, findings provide insights into differentiating the types of cognitive load apparent in hypertext-assisted learning environments. Use of EEG measures allowed examination of instantaneous cognitive load, which showed that leads may be influencing germane load—reducing mental burden associated with creating coherence between two linked node. The self-report of mental effort measure appears more closely associated with overall and intrinsic load.     

Comprehension effects of signalling relationships between documents in search engines

A key task for students learning about a complex topic from multiple documents on the web is to establish the existing rhetorical relations between the documents. Traditional search engines such as Google® display the search results in a listed format, without signalling any relationship between the documents retrieved. New search engines such as Kartoo® go a step further, displaying the results as a constellation of documents, in which the existing relations between pages are made explicit. This presentation format is based on previous studies of single-text comprehension, which demonstrate that providing a graphical overview of the text contents and their relation boosts readers’ comprehension of the topic. We investigated the assumption that graphical overviews can also facilitate multiple-documents comprehension. The present study revealed that undergraduate students reading a set of web pages on climate change comprehended them better when using a search engine that makes explicit the relationships between documents (i.e. Kartoo-like) than when working with a list-like presentation of the same documents (i.e. Google-like). The facilitative effect of a graphical-overview interface was reflected in inter-textual inferential tasks, which required students to integrate key information between documents, even after controlling for readers’ topic interest and background knowledge.     

Cognitive load and instructionally supported learning with provided and learner-generated visualizations

This study investigated, whether learning from science texts can be enhanced by providing learners with different forms of visualizations (pictures) in addition to text. One-hundred-two 9th and 10th graders read a computer-based text on chemical processes of washing and answered questions on cognitive load (mental effort, perceived difficulty) and comprehension (retention, transfer, drawing). Instruction varied according to a 2 × 2-factorial design with ‘learner-generated pictures’ (yes, no) and ‘provided pictures’ (yes, no) as factors. Results indicate positive main effects of provided pictures on all three comprehension measures and negative main effects on both cognitive load measures. Additional analyses revealed a mediation effect of perceived difficulty on retention and transfer, that is learning with provided pictures decreased cognitive load and enhanced comprehension. Furthermore, results show a positive main effect of learner-generated pictures on drawing and mental effort, but no mediation effect. Taken together, computer-based learning with provided pictures enhances comprehension as it seems to promote active processing while reducing extraneous cognitive processing. Learners, generating pictures, however, seem to have less cognitive resources available for essential and generative processing, resulting in reduced comprehension. These results are in line with cognitive load theory, cognitive theories of multimedia learning, and generative theories of learning.     

The effects of text structure and prior knowledge of the learner on computer-based learning

This study is an attempt to investigate the effects of document structure and knowledge level of the reader on reading comprehension, browsing, and perceived control. Four types of texts are distinguished, differing in structure (linear text, hierarchical hypertext, mixed hypertext, and generative text). All the materials were on a PC. In all conditions, participants were allowed 1 h to read through the document. After completing the reading part of the experiment, they were asked to fill out the perceived control questionnaire followed by the reading comprehension test. As far as reading comprehension was concerned, knowledgeable participants had higher reading comprehension scores than non-knowledgeable participants only in the linear text. In addition, there were no significant differences in terms of the reading comprehension scores of the knowledgeable participants among the four topologies. However, the performance of non-knowledgeable participants differed with respect to the type of the topology. In particular, non-knowledgeable participants in the hierarchical and generative conditions performed better than those in the other two conditions. With respect to perceived control, the performance of knowledgeable and non-knowledgeable participants was equivalent in all four conditions. The results are discussed in terms of their implications for the computer-based learning.     

Exploring extraneous cognitive load in an instructional process via the web conferencing system

This study, based on an online instruction via the web conferencing system, explores extraneous cognitive load and its influence on the learning process. Sixty-two sophomore students who enrolled in an online introductory programming course participated in the study. An observation form was used to analyse the course records in video format. Interviews with selected participants were conducted in order to clarify the students’ behaviours during the instructional process. The results indicated that the extraneous cognitive load elements (coherence, redundancy, modality, signalling, and temporal-spatial contiguity) influenced the instructional process. The results suggested that, in web conferencing systems extraneous cognitive load appeared not only from design features of multimedia materials but also the delivery settings. Future work is needed to put forward the influences of the load elements caused in various platforms. The implications and suggestions for instructors who plan to design and teach online courses via web conferencing were also provided.     

RoLo: A dictionary interface that minimizes extraneous cognitive load of lookup and supports incidental and incremental learning of vocabulary

Dictionary use can improve reading comprehension and incidental vocabulary learning. Nevertheless, great extraneous cognitive load imposed by the search process may reduce or even prevent the improvement. With the help of technology, dictionary users can now instantly access the meaning list of a searched word using a mouse click. However, they must spend great cognitive effort identifying the most appropriate meaning for a given context, contributing to the disruption of the flow of reading and decreasing the positive effect of dictionary use. Furthermore, dictionary users face difficulty in exploiting accumulative illustrations from multiple contexts to understand obscure words whose appropriate meanings are not in the dictionary or are difficult to identify. To address these issues and to offer language learners, especially lifelong learners, effective support for incremental and incidental learning of vocabulary through reading, this research proposes a dictionary interface named RoLo (Remind on Lookup). Each time an unfamiliar word is re-looked up, RoLo reminds users about contextual information and word knowledge learned in previous encounters of the word in an appropriate manner. Two studies were conducted to evaluate RoLo. The first study, with 34 participants, examined the effect of RoLo use on incidental vocabulary learning. The second examination, involving 43 participants who used the prototype of RoLo for one month, investigated dictionary users' evaluation of RoLo. The results show that RoLo helps dictionary users enhance vocabulary learning and text comprehension and search for unfamiliar words more easily and faster.     

基于布隆过滤器的RFID数据冗余处理算法研究

RFID技术作为物联网领域的关键技术,具有广阔的应用前景。然而RFID设备在读取标签信息时会产生大量冗余数据。因此,RFID数据冗余处理的研究对于减少RFID中间件系统负荷、快速检测出入标签有着重要的意义。之前针对RFID数据冗余过滤的研究往往是单维度、静态场景的简单过滤,无法实现复杂场景下标签的出入检测。因此,本文提出一种名为时间距离布隆过滤器（TDBF）的算法,该算法从时间和空间两个维度进行冗余过滤。与常用的时间布隆过滤器相比,该算法兼顾了RFID标签的读取时间和读取距离,极大的降低了数据的冗余问题。在保证漏读率较低的情况下,极大的降低了数据的误读率。同时该算法支持动态场景中移动标签的冗余过滤,能够较好的满足出入监控需求。