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Perceptual Multimedia: A Cognitive Style Perspective 197 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Discussion of Results Subject Content Experiment 1 Our analysis has highlighted that the subject content (i.e., particular clip category) has a statistically significant impact on the QoP-IA level of participants (p=.0000). This confirms previous results (Ghinea & Thomas, 1998) and we extended our analysis to include the impact of users cognitive styles. As depicted in Table 4, the clip on which participants performed best varied according to the users cognitive style. Accordingly, intermediate and field-independent users had the highest level of understanding for the Snooker video clip. However, field- dependent users perform better in the Documentary clip. As Table 1 shows, the most discriminating feature between the two clips is the fact that the latter clip does not contain any textual description. The difference in the understanding corresponding to the different cognitive styles is thus probably due to the fact that field-dependent learners are influenced by salient features (Jonassen & Grabowski, 1993, p.88). Without the distraction of text description, field-dependent users could concentrate their learning on video clips, so they could have better performance. On the other hand, irrespective of the type of cognitive style, all users performed worst in the highly dynamic Rugby sports action clip, in which, as Table 4 shows, all media components were medium-strong purveyors of information. This finding seems to imply that users have difficulty concentrating on multiple, different sources of information, and that the dynamism of the clip is also a contributing factor to participants level of understanding, as was confirmed by further analysis, presented in the section titled Degree of Dynamism .. The specific multimedia clip type also influences the QoP-LOE, namely the level of enjoyment experienced by users (p=.0000). As Table 5 shows, although the Documentary and Rugby video clips predominate in the Most Enjoyed and Least Enjoyed categories, only for field-dependent users does the choice of most/least enjoyed clip coincide with the clips on which the level of understanding is highest, respectively lowest (see Table 4, in this regard). These results are in line with those of Fullerton (2000) and Ford and Chen (2001), which showed that field- dependent users performed better in a learning environment matching their preferences; conversely, their performance will be reduced in a mismatched condition. Moreover, our results also show that the Forecast Field Dependent Intermediate Field Independent Best Performance Documentary Snooker 63.84% 62.93% 63.46% Worst Performance Rugby 33.24% 37.5% 34.82% Table 4. Cognitive styles and QoP-IA in clip categories

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196 Ghinea & Chen Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. This study followed Riding s recommendation for the measurements of Field Dependence/ Independence and Verbaliser/Visualiser. In terms of Field Dependence/Independence, Riding s (1991) recommendations are that scores below 1.03 denote fielddependent individuals; scores of 1.36 and above denote field-independent individuals; students scoring between 1.03 and 1.35 are classed as Intermediate. Regarding the measurement of Verbaliser/Visualiser, the recommendations are scores below 0.98 denote verbalisers; scores of 1.09 and above denote visualisers; students scoring between 0.98 and 1.09 are classed as biomodal. Procedure The experiment consisted of several steps. Initially, the CSA was used to classify users cognitive styles as Field Dependent /Intermediate/Field Independent (Experiment 1) or Verbaliser/Biomodal/Visualiser (Experiment 2). Subjects then viewed the 12 multimedia video clips. In order to counteract any order effects, the order in which clips were visualised was varied randomly for each participant. After the users had seen each clip once, the window was closed, and they had to answer a number of questions about the video clip they had just seen. The actual number of such questions depended on the video clip, and varied between 10 and 12. After the user had answered the set of questions pertaining to a particular video clip and the responses had been duly recorded, (s)he was asked to rate the enjoyment quality of the clip that had just been seen on a Likert scale of 1 - 6 (with scores of 1 and 6 representing the worst and, respectively, best perceived qualities possible). The user then went on and watched the next clip. Users were instructed not to let personal bias towards the subject matter in the clip or production-related preferences (for instance, the way in which movie cuts had been made) influence their enjoyment quality rating of a clip. Instead, they were asked to judge a clip s enjoyment quality by the degree to which they, the users, felt that they would be satisfied with a general purpose multimedia service of such quality. Users were told that factors which should influence their quality rating of a clip included clarity and acceptability of audio signals, lip synchronisation during speech, and the general relationship between visual and auditory message components. Data Analyses In this study, the independent variables include the participants cognitive styles, as well as clip categories and their degree of dynamism. The dependent variables were the two components of Quality of Perception: the level of understanding (QoP-IA, expressed as a percentage measure describing the proportion of questions that the user had correctly answered for each clip) as well as the level of enjoyment (QoP-LOE, expressed on a sixpoint Likert scale). Data were analysed with the Statistical Package for the Social Sciences (SPSS) for Windows version (release 9.0). An ANalysis Of VAriance (ANOVA), suitable to test the significant differences of three or more categories, and t-test, suitable to identify the differences between two categories (Stephen & Hornby, 1997), were applied to analyse the participants responses. A significance level of p < 0.05 was adopted for the study.

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194 Ghinea & Chen Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Research Instruments Video Clips A total of 12 video clips were used in our study. The multimedia clips were visualised under a Microsoft Internet Explorer browser with a Microsoft Media player plug-in, with users subsequently filling in a Web-based questionnaire to evaluate QoP for each clip. These 12 clips had been used in previous QoP experiments (Ghinea & Thomas, 1998), and were between 30-44 seconds long and digitised in MPEG-1 format. The subject matter VIDEO CATEGORY Dynamic Audio Video Text 1 - Action Movie Strong Medium Strong Weak/None 2 - Animated Clip Medium Medium Strong Weak/None 3 - Band Clip Medium Strong Mediu Weak/None 4 - Chorus Clip Weak Strong Mediu Weak/None 5 - Commercial/Ad Clip Medium Strong Strong Medium 6 - Cooking Clip Weak Strong Strong Weak/None 7 - Documentary Clip Medium Strong Strong Weak/None 8 - News Clip Weak Strong Strong Medium 9 - Pop Music Clip Medium Strong Strong Strong 10 Rugby Clip Strong Medium Strong Medium 11 - Snooker Clip Weak Medium Mediu Strong 12 - Weather Forecast Clip Weak Strong Strong Strong Table 3. Video categories used in experiments Figure 1. Snapshots of clips used in experiments

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Perceptual Multimedia: A Cognitive Style Perspective 195 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. they portrayed was varied (as detailed in Table 3 and Figure 1) and taken from selected television programmes, thereby reflecting informational and entertainment sources that average users might encounter in their everyday lives. Thus, six of the clips (2, 5, 6, 7, 8, and 12 in Table 1) comprised predominantly informational content, with the remainder of the clips being viewed mainly for entertainment purposes. Also varied was the dynamism of the clips (i.e., the rate of change between the frames of the clip), which ranged from a relatively static news clip to a highly dynamic space action movie. Table 3 also describes the importance, within the context of each clip, of the audio, video, and textual components as purveyors of information, as previously established through user tests (Ghinea & Thomas, 1998). Cognitive Style Analysis The cognitive style dimensions investigated in this study include Field Dependence/ Independence and Verbaliser/Visualiser. A number of instruments have been developed to measure these two dimensions. Riding s (1991) Cognitive Style Analysis (CSA) was applied to identify each participant s cognitive styles in this study, because the CSA offers computerised administration and scoring. In addition, the CSA can offer various English versions, including Australasian, North American, and United Kingdom contexts. The CSA uses two sub-tests to identify Field Dependence/Independence. The first presents items containing pairs of complex geometrical figures that the individual is required to judge as either the same or different. The second presents items each comprising a simple geometrical shape, such as a square or a triangle, and a complex geometrical figure, as in the GEFT, and the individual is asked to indicate whether or not the simple shape is contained in a complex one by pressing one of two marked response keys (Riding & Grimley, 1999).. The first sub-test is a task requiring field-dependent capacity. Conversely, the second sub-test requires the disembedding capacity associated with field-independence. The CSA uses two types of statement to measure the Verbal-Imagery dimension and asks participants to judge whether the statements are true or false. The first type of statement contains information about conceptual categories while the second describes the appearance of items. There are 48 statements in total covering both types of statement. Each type of statement has an equal number of true statements and false statements. It is assumed that visualisers respond more quickly to the appearance statements, because the objects can be readily represented as mental pictures and the information for the comparison can be obtained directly and rapidly from these images. In the case of the conceptual category items, it is assumed that verbalisers have a shorter response time because the semantic conceptual category membership is verbally abstract in nature and cannot be represented in visual form. The computer records the response time to each statement and calculates the Verbal-Visualiser Ratio. A low ratio corresponds to a verbaliser and a high ratio to a visualiser, with the intermediate position being described as biomodal.

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Perceptual Multimedia: A Cognitive Style Perspective 193 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Measuring Subjective Level of Enjoyment (QoP-LOE) The subjective level of enjoyment (QoP-LOE) experienced by a user when watching a multimedia presentation, was polled by asking users to express, on a scale of 1-6, how much they enjoyed the presentation (with scores of 1 and 6 respectively representing no and absolute user satisfaction with the multimedia video presentation). In keeping with the methodology followed by Apteker et al (1995), users were instructed not to let personal bias towards the subject matter in the clip or production-related preferences (for instance, the way in which movie cuts had been made) influence their enjoyment quality rating of a clip. Instead, they were asked to judge a clip s enjoyment quality by the degree to which they, the users, felt that they would be satisfied with a general purpose multimedia service of such quality. Users were told that factors which should influence their quality rating of a clip included clarity and acceptability of audio signals, lip synchronisation during speech, and the general relationship between visual and auditory message components. This information was also subsequently used to determine whether ability to assimilate information has any relation to user level of enjoyment, the second essential constituent (beside information analysis, synthesis, and assimilation) of QoP. Participants This chapter brings together the results of two empirical studies conducted at Brunel University s School of Information Systems, Computing, and Mathematics. In the first study, participants cognitive styles were categorised according to the Field Dependent/ Independent dimension, while in the second, participants cognitive styles were categorised using the Verbaliser/Visualiser dimension. Experiment 1 Sixty-six subjects participated in this study. Despite the fact that the participants volunteered to take part in the experiment, they were extremely evenly distributed in terms of cognitive styles, including 22 field-independent users, 22 intermediate users, and 22 field-dependent users. In terms of gender, there were 34 male users and 32 female users. Experiment 2 This study involved 71 participants, which turned out to be quite evenly distributed in terms of cognitive styles, including 23 field-independent users, 25 intermediate users, and 23 field- dependent users. Moreover, participant breakdown according to gender was also quite evenly matched (37 males and 34 females). For both studies, all participating users were inexperienced in the content domain of the multimedia video clips visualised as part of our experiments, which will be described next.

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192 Ghinea & Chen Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. environments (distance learning and CSCW, to name but two) and ultimately help in the elaboration of robust user models which could be used to develop applications that meet with individual needs. Methodology Design Overview This chapter reports the results of studies which investigated how different multimedia content is perceived by different cognitive style dimensions. Perceived multimedia quality was examined using the QoP measure, the only such metric that takes into account multimedia s infotainment duality. Measuring QoP As previously mentioned, QoP has two components: an information analysis, synthesis, and assimilation part (henceforth denoted by QoP-IA) and a subjective level of enjoyment (henceforth denoted by QoP-LOE). To understand QoP in the context of our work, it is important to explain how both these components were defined and measured. Measuring Information Assimilation (QoP-IA) In our approach, QoP-IA was expressed as a percentage measure, which reflected a user s level of information assimilated from visualised multimedia content. Thus, after watching a particular multimedia clip, the user was asked a standard number of questions (10, in our case) which examined information being conveyed in the clip just seen, and QoP-IA was calculated as being the proportion of correct answers that users gave to these questions. All such questions asked must, of course, have definite answers, for example: (from the Rugby video clip used in our experiments) What teams are playing? had an unambiguous answer (England and New Zealand) which had been presented in the multimedia clip, and it was therefore possible to determine if a participant had answered this correctly or not. Thus, by calculating the percentage of correctly-absorbed information from different information sources, it was possible to determine from which information sources participants absorbed the most information. Using this data, it is possible to determine and compare, over a range of multimedia content, potential differences that might exist in QoP-IA.

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Perceptual Multimedia: A Cognitive Style Perspective 191 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. of the object. Field-dependent individuals rely more on external references; by contrast, field-independent individuals rely more on internal references (Witkin, Moore, Goodenough, & Cox, 1977). The differences between field-independent and fielddependent users are summarized in Table 1. The main difference between visualiser/verbaliser focuses on a preference for learning with words versus pictures. A visualiser would prefer to receive information via graphics, pictures, and images, whereas a verbaliser would prefer to process information in the form of words, either written or spoken (Jonassen & Grabowski, 1993). In addition, visualisers prefer to process information by seeing, and they will learn most easily through visual and verbal presentations, rather than through an exclusively verbal medium. Moreover, their visual memory is much stronger than their verbal. On the other hand, verbalisers prefer to process information through words, and find they learn most easily by listening and talking (Laing, 2001). Their differences are summarised in Table 2. These two dimensions of cognitive styles have been investigated by several works in learning environments. For example, a study by Chuang (1999) produced four-courseware versions: animation+text, animation+voice, animation+text+voice, and free choice. The result showed that field-independent subjects in the animation+text+voice group or in the free choice group scored significantly higher than those did in the animation+text group or in the animation+voice group. No significant presentation effect was found for the field-dependent subjects. Furthermore, Riding and Douglas (1993), with 15-16-yearold students, found that the computer-presentation of material on motorcar braking systems in a Text-plus-Picture format facilitated the learning by visualisers compared with the same content in a Text-plus-Text version. They further found that in the recall task in the Text-plus-Picture condition, 50% of the visualisers used illustrations as part of their answers, compared to only 12% of the verbalisers. Generally, visualisers learn best from pictorial presentations, while verbalisers learn best from verbal presentations. However, paucity of study investigates the relationship between the use patterns of these two dimensions of cognitive styles in multimedia systems in general, and specifically in distributed multimedia systems, where quality fluctuations can occur owing to dynamically varying network conditions. As the QoP metric is one which has an integrated view of user-perceived multimedia quality in such distributed systems, it is of particular interest to investigate the impact of cognitive styles on QoS-mediated QoP, as it will help in achieving a better understanding of the factors involved in such Visualisers Verbalisers Think concretely Think abstractly Have high imagery ability and vivid daydreams Have low imagery ability Like illustrations, diagrams, and charts Like reading text or listening Prefer to be shown how to do something Prefer to read about how to do something Are more subjective about what they are learning Are more objective about what they are learning Table 2. The differences between visualisers and verbalisers (Adapted from Jonassen & Grabowski, 1993; Riding & Rayner, 1998)

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Perceptual Multimedia: A Cognitive Style Perspective 189 Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Theoretical Background Quality of Service The networking foundation on which current distributed multimedia applications are built either do not specify QoS parameters (also known as best effort service) or specify them in terms of traffic engineering parameters such as delay, jitter, and loss or error rates. However, these parameters do not convey application-specific needs such as the influence of clip content and informational load on the user multimedia experience. Furthermore, traditional approaches of providing QoS to multimedia applications have focused on ways and means of ensuring and managing different technical parameters such as delay, jitter, and packet loss over unreliable networks. To a multimedia user, however, these parameters have little immediate meaning or impact. Although (s)he might be slightly annoyed at the lack of synchronisation between audio and video streams, it is highly unlikely that (s)he will notice, for instance, the loss of a video frame out of the 25 which could be transmitted during a second of footage, especially if the multimedia video in question is one in which the difference between successive frames is small. Moreover, in a distributed setting, the underlying communication system will not be able to provide an optimum QoS due to two competing factors, multimedia data sizes and network bandwidth. This results in phenomena such as congestion, packet loss, and errors. However, little work has been reported on the relationship between the network provided QoS and the satisfaction and perception of the user. While the QoS impacts upon the perceived multimedia quality in distributed systems, previous work examining the influence of varying QoS on user perceptions of quality has almost totally neglected multimedia s infotainment quality (i.e., a mixture of both of informational as well as entertainment content), and has concentrated primarily on the perceived entertainment value of presentations displayed with varying QoS parameters. Accordingly, previous work has studied the impact of varying clip frame rates on the user s enjoyment of multimedia applications (Apteker, Fisher, Kisimov, & Neishlos, 1995; Fukuda, Wakamiya, Murata, & Miyahara, 1997), and it has been shown that the dependency between human satisfaction and the required bandwidth of multimedia clips is non-linear. Consequently, a small change in human receptivity leads to a much larger relative variation of the required bandwidth. From a different perspective, Wijesekera and Srivastava (1996) and Wijesekera, Srivastava, Nerode, and Foresti (1999) have examined the effect that random media losses have on the user-perceived quality. Their work showed that missing a few media units will not be negatively perceived by a user, as long as too many such units are not missed consecutively and that this occurrence is infrequent. Moreover, because of the bursty nature of human speech (i.e. talk periods interspersed with intervals of silence), audio loss is tolerated quite well by humans as it results merely in silence elimination (21% audio loss did not provoke user discontent (Wijesekera et al., 1999). However, viewer discontent for aggregate video losses increases gradually with the amount of losses, while for other types of losses and synchronisation defects, there is an initial sharp rise in viewer annoyance that afterwards plateaus out.

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190 Ghinea & Chen Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Further work has been undertaken by Steinmetz (1996) who explored the bounds within which lip synchronisation can fluctuate without undue annoyance on the viewer s part, while the establishment of metrics for subjective assessment of teleconferencing applications was explored in Watson and Sasse (1996). Indeed, the correlation between a user s subjective ratings of differing-quality multimedia presentation and physiological indicators has been studied by Wilson and Sasse (2000). However, research has largely ignored the influence that the user s psychological factors have on the perceived quality of distributed multimedia. The focus of our research has been the enhancement of the traditional view of QoS with a user-level defined QoP. This is a measure that encompasses not only a user s satisfaction with multimedia clips, but also his/her ability to perceive, synthesise, and analyse the informational content of such presentations. As such, we have investigated the interaction between QoP and QoS and its implications from both a user perspective as well as from a networking angle. Cognitive Styles Cognitive style is an individual s characteristic and consistent approach to organising and processing information. Riding and Rayner (1998) defined cognitive style as an individual preferred and habitual approach to organising and representing information (p.25). Among a variety of cognitive styles, Field Dependence/Independence and Visualiser/Verbaliser are related to perceptual multimedia. The former concerns how users process and organise information, whereas the latter emphasises on how users perceive the presentation of information. Field Dependence/Independence is related to the degree to which a learner s perception or comprehension of information is affected by the surrounding perceptual or contextual field (Jonassen & Grabowski, 1993, p. 87). Field-dependent people tend to perceive objects as a whole, whereas Field -independent people focus more on individual parts Field Dependent Learners Field Independent Learners They are externally directed and are easily influenced by salient features. They are internally directed and process information with their own structure. They experience surroundings in a relatively global fashion and struggle with individual elements. They experience surroundings analytically and are good with problems that require taking elements out of their whole context. They are more likely to accept ideas as presented. They are more likely to accept ideas only strengthened through analysis. Table 1. The differences between field-dependent and field-independent learners (Adapted from Jonassen & Grabowski, 1993; Riding & Rayner, 1998)

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188 Ghinea & Chen Copyright 2006, Idea Group Inc. Copying or distributing in print or electronic forms without written permission of Idea Group Inc. is prohibited. Introduction Multimedia has been identified as a potential method of improving the learning process in particular and the user computing experience in general. Its use encourages user interaction, thus ensuring that users cannot become a passive participant of the learning experience (Neo & Neo, 2004). Not only does the use of multimedia in applications increase interaction levels, but increases interest, motivation, and retention of information (Demetriadis, Triantafilou, & Pombortis, 2003). Moreover, the fact that students seem to prefer the use of multimedia for teaching to the standard teacher-student paradigm as it is more user-centred (Zwyno, 2003), comes as no surprise. The potential of multimedia has, to date, not been fully realised. Users perceive, process, and organise information in individualistic ways, yet current multimedia applications routinely fail to take this into consideration (Stash, Cristea, & De Bra, 2004). We therefore believe that the effectiveness of a multimedia presentation would be hindered if it did not include the user experience in terms of enjoyment and information assimilation. Key to this is the issue of the quality of the multimedia presentation. Quality, in our perspective, has two main facets in a distributed multimedia environment: of service and of perception. The former, Quality of Service (QoS), illustrates the technical side of computer networking and represents the performance properties that the underlying network is able to provide. The latter, Quality of Perception (QoP), characterises the perceptual experience of the user when interacting with multimedia applications. While the quality delivered by communication networks has traditionally been measured using QoS metrics, we believe that, as users are consumers of multimedia applications, it is their opinions about the quality of multimedia material visualised which ultimately measures the success (or indeed, failure) of such applications to deliver desktop instruction material. When this delivery is done over Wide Area Networks such as the World Wide Web ( the Web ), transmission of multimedia data has to accommodate not only user subjective preferences, but also fluctuating networking environments. The other concern is whether distributed multimedia presentations can accommodate individual differences. Previous studies indicate that users with different characteristics have different perceptions of multimedia presentation (Chen & Angelides, 2003). In particular, different cognitive style groups benefit from different types of multimedia presentation. Therefore, empirical evaluation that examines the impact of cognitive styles becomes paramount because such evaluations can provide concrete prescriptions for developing learner-centred systems that can match the particular needs of each cognitive style group. While QoP has been investigated in the context of distributed multimedia quality (Ghinea & Thomas, 2005), the study did not take into account the possible effect of users cognitive styles on their QoP. In this chapter, we present the results of studies which looked at how multimedia content is perceived by different cognitive style groups. Accordingly, the chapter begins by building a theoretical background to present previous work in the area of subjective distributed multimedia quality and to discuss the influence of cognitive style on user perception of multimedia presentations. It then describes and discusses the findings of our empirical studies. The chapter ends with conclusions being drawn, highlighting the value of integrating QoP considerations with users cognitive styles in the delivery of distributed multimedia presentations.

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