The impact of two different think-aloud instructions in a usability test: a case of just following orders?

The instructions used in think-aloud studies can range from a simple request to think-aloud, to an explicit instruction to include certain types of content. The present study compared two think-aloud instructions: the classic neutral think-aloud instruction and an explicit instruction requesting explanations and content that is relevant to the user experience. Data from task performance, mental workload, think-aloud protocols and usability problems were collected from 16 participants, equally distributed between the two think-aloud instruction conditions. No differences were found in task performance, however, participants in the explicit instruction condition reported higher mental workload and a focus on finding interface problems. The explicit instruction condition also yielded more utterances about the user experience, expectations and explanations of behaviour than the neutral condition. An analysis of the resultant usability problems revealed that the explicit instruction led to a larger number of dialogue, navigation, layout and functionality problems, but that the problems which were unique to this condition were, in the main, at a low level of severity.     

The effects of source representation and goal instructions on college students' information evaluation behavior change

We investigated ways of scaffolding information evaluation behavior (IEB) in online inquiry contexts. Previous instructional support simplified IEB and rarely critically addressed the cognitive load that accompanies multiple representations or naïve task perception that hinders critical evaluation. We conducted a longitudinal, 2 × 2 quasi-experimental study in an introductory college biology course, varying (A) Source Representation Scaffolds to address limited cue awareness and cognitive load and (B) Goal Instructions to address task perception. For treatment A, students were given an annotation tool in addition to a checklist (Control A). For treatment B, instead of persuasion goal instructions (Control B), written task directions prompted student to consider alternative ideas (balanced reasoning goals). We measured students' IEB four times. We also measured individual task perception and cognitive capacity. Multilevel analyses identified the specific nature of changes in IEB. On average, IEB did not improve much in the baseline group while task perception and cognitive capacity differentiated IEB scores. Conversely, both annotation and balanced reasoning goals yielded improved gains in IEB, but there was a negative interaction effect when they were combined. The results demonstrate the benefits of annotation and balanced reasoning goals but suggest the need to address possible difficulties in using multiple scaffolds.     

Comparative dynamics in an overlapping-generations model: the effects of quasi-rational discrete choice on finding and maintaining Nash equilibrium

Many models of Nash Equilibrium are complex enough that it becomes difficult to ascertain if and under what conditions the economic players can find and maintain this equilibrium. Using an analytical overlapping- generations model of goods, labor, and banking markets and quasi-rational discrete choice decision making, we find through agent-based simulations that Nash Equilibrium in goods market prices is stable when firms are sufficiently sensitive to changes in profits. In addition to verifying the analytical Nash outcome, the simulations verify that their economic agents, decision rules, and other protocols correspond to and maintain consistency with the analytical theory and identify important bounds of the analytical model.      

Delaying elaborated feedback within computer-based learning environments: The role of summative and question-based feedback

Elaborative feedback (EF) containing explanations on students' responses benefits learning. Computer-based environments provide learners with EF in different ways, for example, on an immediate question-by-question basis or after answering a set of questions. Recent findings also suggest that delaying EF enhances learning. However, it is unclear to what extent different types of delayed-EF favour students' performance. This study examines whether and how two types of delayed-EF (question-based vs. summative) influence students' question-answering performance and final learning over immediate-EF. One hundred thirty-three secondary-school students read a scientific text and answered 12 multiple-choice questions in a computer-based environment. A day later, students completed a final learning test with 20 open-ended questions. Results showed that neither question-based delayed EF nor summative delayed EF outperformed immediate EF. However, EF moderated the relationship between students' prior knowledge and their performance outcomes, suggesting that students with higher levels of prior knowledge receiving summative delayed EF benefited more.     

Designing electronic feedback – Analyzing the effects of social presence on perceived feedback usefulness

Feedback interventions, i.e. actions taken by (an) external agent(s) to provide information regarding one׳s task performance, are an important element in motivating and raising performance. Especially the perceived feedback usefulness determines its positive effects. In today׳s digitalized world, feedback is more often given electronically, i.e. computer-mediated or even automated by computer systems. Those feedback interventions׳ effect on perceptions resulting from the difference of communication media is essentially considered by the concept of social presence. However, information systems (IS) research lacks a structured evaluation of possible design choices of feedback media, their influence on the social presence and subsequent effect on the perceived feedback usefulness. To close this research gap, we conduct a laboratory experiment with 43 participants in which we analyze six different design choices for feedback media. We applied a 2×3 experimental design covering the feedback source (human, non-human feedback) and media richness (text, audio, and video). We show that social presence directly and mediated by the perceived trustworthiness of feedback on simple IT-based tasks impacts perceived feedback usefulness. Our study concludes by outlining opportunities for future research and practical implications for human and non-human (i.e. automated) feedback.     

非线性时滞反馈实现离散神经元网络的去同步化

采用非线性时滞反馈实现离散神经元网络的去同步化控制．对于由映射神经元模型构建的神经网络，调节神经元之间的连接强度可以实现网络的混沌簇放电同步．在神经元的快变量中施加非线性时滞反馈信号可以实现网络的完全去同步化，且不改变神经元本身的放电特性．与线性时滞反馈相比，非线性时滞反馈能够实现强连接神经网络的去同步化，且对于参数的变化具有鲁棒性．     

Decentralized state feedback control of discrete event systems

In this paper, we consider decentralized state feedback control of discrete event systems with a (global) control specification given by a predicate. In this framework, instead of a global state feedback, each local state feedback controls a part of the system according to local information so that global behaviors satisfy the global control specification. We introduce the notion of n-observability of predicates, and present necessary and sufficient conditions for the existence of a decentralized state feedback which achieves the global control specification.     

Stabilization and blocking in state feedback control of discrete event systems

We consider controlled discrete event systems modeled by the Ramadge-Wonham model, with a control specification given in terms of both admissible and target states. We define blocking in state feedback control using the notion of stability of discrete event systems. Intuitively, a system is said to be blocking if some trajectories of admissible states cannot reach target states. For control-invariant predicates we define two performance measures called a prestabilizing measure and a blocking measure. First, we present an algorithm to compute the minimally restrictive nonblocking solution. But the nonblocking solution may be restrictive. Then we present design methods to improve the two performance measures. And we show that the task of logical optimization of a blocking feedback can be done by two steps.     

State feedback control of real-time discrete event systems with infinite states

In this paper, we study a state feedback supervisory control of timed discrete event systems (TDESs) with infinite number of states modelled as timed automata. To this end, we represent a timed automaton with infinite number of untimed states (called locations) by a finite set of conditional assignment statements. Predicates and predicate transformers are employed to finitely represent the behaviour and specification of a TDES with infinite number of locations. In addition, the notion of clock regions in timed automata is used to identify the reachable states of a TDES with an infinite time space. For a real-time specification described as a predicate, we present the controllability condition for the existence of a state feedback supervisor that restricts the behaviour of the controlled TDES within the specification.     

一类离散混沌系统的脉冲时滞反馈控制

为了镇定一类离散混沌系统的不稳定周期轨道,提出脉冲时滞反馈控制方法.系统地研究了脉冲时滞反馈控制方法在一类离散小世界网络模型中的应用问题.数值仿真结果表明,小世界网络模型中的倍周期分岔及其导致的混沌可以被延后,镶嵌在混沌吸引子内部的不稳定周期轨道可以被镇定.与已有相关控制方法相比,所提出的脉冲时滞反馈控制方法具有适用范围广泛、实现过程简单方便且灵活等优势.     

Direct discrete time design of robust state derivative feedback control laws

This paper is concerned with the problem of designing robust state derivative feedback control laws in discrete time. The main contribution consists of a method for recasting a continuous time state space model in the form of a discrete time model formulated in terms of the state derivative. Uncertain input delays and parametric uncertainties in polytopic form can be propagated from the original state space representation to the resulting state derivative model. Therefore, robust control techniques originally developed for discrete time state space models can be directly employed to design the state derivative feedback law. Three computational examples are presented for illustration. The first example highlights the importance of accounting for the effect of sampling in the design procedure. More specifically, a linear quadratic regulation problem involving the state derivative is addressed. The second example involves the design of a robust predictive controller in the presence of input constraints and uncertain time delay. Finally, the third example is concerned with robust pole placement in the presence of parametric uncertainty.     

基于微电流刺激的多强度分级虚拟触觉反馈

触觉反馈可以有效提高用户的虚拟现实交互的沉浸感,但是采用振动方式的触觉反馈存在反馈模态单一的缺陷;采用机械传动式、微流驱动方式的触觉反馈存在结构复杂、难以集成等缺陷. 微电流触觉反馈具有集成度高、反馈模态丰富等优点,但是存在反馈强度识别准确率不够和长时间作用下易造成不适感等问题. 为了解决这些问题,设计了基于微电流刺激的新型多强度电触觉反馈系统,通过研究电流参数、电极阵列和接地电极等影响因素,并引入双相电流脉冲,优化电流正负电荷量比值等方式,确定了该系统的刺激模式. 35名受试者的心理物理学实验结果表明该反馈系统能够在有效减少微电流刺激带来不适的同时实现93.3%和81.7%的四级和五级强度识别准确率,优于传统方法,这可能是具有广泛应用场景的触觉反馈设备.

     

基于LMI不确定离散随机系统输出反馈保性能控制

针对一类范数有界不确定离散随机系统,研究了具有输出反馈控制器的保性能控制,由此得到闭环系统的二次型性能指标上界的一般形式;然后应用LMI凸优化技术,推导出使闭环系统渐近稳定的最优保性能控制器的设计方法;最后通过仿真算例验证了所提出算法的可行性和有效性.     

Some insights into the impact of affective information when delivering feedback to students

ABSTRACT

The relation between affect-driven feedback and engagement on a given task has been largely investigated. This relation can be used to make personalised instructional decisions and/or modify the affect content within the feedback. However, although it is generally assumed that providing encouraging feedback to students should help them adopt a state of flow, there are instances where those messages might result counterproductive. In this paper, we present a case study with 48 secondary school students using an Intelligent Tutoring System for arithmetical word problem solving. This system, which makes some common assumptions on how to relate affective state with performance, takes into account subjective (user's affective state) and objective information (previous problem performance) to decide the upcoming difficulty levels and the type of affective feedback to be delivered. Surprisingly, results revealed that feedback was more effective when no emotional content was included, and lead to the conclusion that purely instructional and concise help messages are more important than the emotional reinforcement contained therein. This finding shows that this is still an open issue. Different settings present different constraints generating related compounding factors that affect obtained results. This research confirms that new approaches are required to determine when, how and where affect-driven feedback is needed. Affect-driven feedback, engagement and their mutual relation have been largely investigated. Student's interactions combined with their emotional state can be used to make personalised instructional decisions and/or modify the affect content within the feedback, aiming to entice engagement on the task. However, although it is generally assumed that providing encouraging feedback to the students should help them adopt a state of flow, there are instances where those encouraging messages might result counterproductive. In this paper, we analyze these issues in terms of a case study with 48 secondary school students using an Intelligent Tutoring System for arithmetical word problem solving. This system, which makes some common assumptions on how to relate affective state with performance, takes into account subjective (user's affective state) and objective (previous problem performance) information to decide the difficulty level of the next exercise and the type of affective feedback to be delivered. Surprisingly, findings revealed that feedback was more effective when no emotional content was included in the messages, and lead to the conclusion that purely instructional and concise help messages are more important than the emotional reinforcement contained therein. This finding, which coincides with related work, shows that this is still an open issue. Different settings present different constraints and there are related compounding factors that affect obtained results, such as the message's contents and their target, how to measure the effect of the message on engagement through affective variables considering other issues involved, and to what extent engagement can be manipulated solely in terms of affective feedback. The contribution here is that this research confirms that new approaches are needed to determine when, how and where affect-driven feedback is needed. In particular, based on our previous experience in developing educational recommender systems, we suggest the combination of user-centred design methodologies with data mining methods to yield a more effective feedback.     

一类离散不确定时滞系统的输出反馈变结构控制

针对一类离散不确定时滞系统,提出一种输出反馈变结构控制算法,该算法使系统状态无需完全可测.通过研究离散不确定时滞系统的简约型,基于LMI技术给出了滑模平面的设计方法,推导出了稳定的滑模面存在的充分条件,并将参数不确定性的影响等效为名义时滞系统的外界干扰,利用时延技术对干扰进行在线估计,从而抵消掉系统中的不确定性.采用离散趋近律的方法设计控制律,并通过仿真算例验证了所提出算法的有效性.     

Modular nonblocking state feedback control of discrete event systems and its application to dynamic oligopolistic markets

This article addresses a modular state feedback supervisory control problem where two local controllers should achieve a common control objective against another local controller. Each local controller has its own control objective described as a predicate. This article also addresses a nonblocking modular control problem in which a discrete event system controlled by three local controllers tends to reach the common marked states of two local controllers that are, however, prohibited by the third local controller. For a case study, we apply the proposed theory to an oligopolistic market composed of two firms and one government. Two oligopolistic firms have a common objective to maximise their total profit through collusion. However, the government prevents them from engaging in collusion. We show that the modular supervisory control theory presented in this article can be used to solve the problem of ‘how can the firms maximise their total profit against the intervention of government’?     

Path following using transverse feedback linearization: Application to a maglev positioning system

This article presents an approach to path following control design based on transverse feedback linearization. A “transversal” controller is designed to drive the output of the plant to the path. A “tangential” controller meets the application-specific requirements on the path, such as speed regulation and internal stability. This methodology is applied to a five-degree-of-freedom (5-DOF) magnetically levitated positioning system. Experimental results are provided that demonstrate the effectiveness of our control design.     

The paradoxical effects of legal intervention over unethical information technology use: A rational choice theory perspective

While the IS literature offers rich insights into the kinds, causes and consequences of unethical information technology use (UITU), we know little about the degree to which legal intervention may mitigate UITU. Our research aims at understanding how legal intervention could mitigate UITU by influencing the cost-benefit analysis in determining the decision to commit such unethical use of IT. Our contributions are twofold. First, we provide testable propositions on the role of legal intervention. Second, we offer an innovative take on intervention – conceived as a multi-mechanism process that adapts to UITU as well as to the way IT users negotiate the IT artifact.     

The effect of advertisement choice on attention

The purpose of this study was to assess the effect of advertisement choice on individuals’ subsequent attention towards the advertisement. Participants in this study decided which type of advertisement to watch or they were not given a choice. Results of the study showed that advertisement choice significantly influenced female participants’ subsequent attention towards the advertisement but not males’. This effect suggests that this marketing technique should be used in specific situations to target women predominately. These include marketing products predominately or universally used by females or during shows which are viewed by a large number of females.     

The importance of usability in product choice: A mobile phone case study

Usability has become established as an important aspect of product design. This paper describes an investigation that was carried out to identify the importance of usability in product choice related to other product attributes. Interviews were initially carried out to identify possible attributes that contribute to product choice. Experiments were then undertaken using the methods of active information search, structured preference elicitation, ranking and interviews in order to find out what attributes were important to people when choosing an example product – mobile phones. It was found that usability is indeed important in product choice but perhaps not as much as users themselves believe. Other attributes that were found to be more important were features, aesthetics and cost. The process of product choice was found to be complex and it may be the case that people have come to expect usability in their products. Further research is needed to understand more fully the changing role of usability in product choice and to further improve the quality of the user–product relationship.