Preferences for different CBI text screen designs based on the density level and realism of the lesson content viewed

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Computers in Human Behavior. Vol. 10, No. 4, pp. 593-603. 1994 Copyright (B 1994 Ekvier Science Ltd Printed in the USA. All tights reserved

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Preferences for Different CBI Text Screen Designs Based on the Density Level and Realism of the Lesson Content Viewed

Steven lb% Ross, Gary 17. ~offisoff, and Charles FK Schultz

Memphis State University

Abstract - College student subjects indicated preferences for learning from computer-based instruction (CBI) text screen designs representing four di~erent levels of screen densi~. conditions for the presentations were varied on the basis of the number of screens presented for each density level (single screen vs. multiple frames) and the realism of the text content viewed (nonsense, approximation-to-English, and actual lesson). Results showed similar patterns for both single and multiple frames, reflecting a tendency by subjects to favor middle to low density presentations with the artificial text forms, but middle to high density presentations with realistic text. The suggestion is that when artificial stimulus materials are used in instructional design preference studies, aesthetic properties may become more salient in the absence of cues for judging the role of supporting context (high density text) in conveying meaning. The implications of this idea for practice and research on computer screen design are discusses

In considering the best ways to design text screens in computer-based instruction (CBI), it is often taken for granted that the greater the amount of white space on the screen the more readable the content (Allessi & Trollip, 1984; Bork, 1987; Grabinger, 1983; Heines, 1984; Hopper & Hannafin, 1986). Thus, display formats such as double-spacing and wide margins are commonly recommended. Intuitively,

Requests for reprints should be addressed to Steven M. Ross, Counseling, Research, and Educational Psychology, University of Memphis, Memphis, TN 38152.

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594 Ross, Morrison, and Schultz

these design conventions are logical choices considering the limited area of a computer screen compared to that of a print page (Fish & Feldmann, 1987; Muter, Latremouille, & Treurniet, 1982). Due to this latter constraint, packing a large amount of information on a single screen may increase the difficulty of recognizing characters and words, while producing visual strain over the duration of a lesson (Bat-be & Milone, 1984).

In support of this reasoning, prior research has shown that performance error rates in reading instrumentation and information displays increase as the density of the display increases (Burns & Bozeman, 1979; Coffey, 1961; Mackworth, 1976; Ringel & Hamer, 1964). In such studies, density was defined by calculating the percentage of the available screen spaces that contain a character or are adja- cent to a character. In addition to the possible advantages of lower density displays for performance, Grabinger (1983) found, using paired comparisons of different screen presentation formats, that some students preferred “spacier” designs (e.g., wide margins) over denser ones (e.g., single spacing); a larger group, however, preferred denser screens provided the display was organized, visually appealing, and balanced. To eliminate stimulus meaning as a possible contaminat- ing factor, Grabinger used nonsense material rather than actual text to represent the screen content.

Morrison, Ross, Schultz, and O’Dell (1989) recently called attention to limita- tions of the foregoing studies for generalizing to realistic classroom or training contexts. First, where instrumentation or information displays are used (Danchack, 1976; Smith, 1980, 1981, 1982; NASA, 1980), task requirements and expectancies may contrast sharply with those likely to be associated with learning from expository text. Specifically, factors that maximize accuracy in reading data from an instrument panel seem quite different from those likely to promote meaningful understanding in reading an explanation of a concept. Low density screens defi- nitely appear desirable for the former case, but the situation is not as obvious for the latter. Second, where artificial stimulus material is used to increase the internal validity of research findings, external validity (i.e., generalizability to practice) may be low. For example, in Grabinger’s (1983) screen preference study, subjects reacted to “content-free” designs (i.e., using X’s and O’s to replace actual characters, as described by Twyman, 1981) presented on isolated individual screens. One external validity concern is that isolated screens do not convey the increases in lesson length (number of frames) that automatically result when screen density is reduced but the amount of lesson context is fixed. Another concern is that subjects may prefer wide margins and other low density attributes due to the greater saliency of aesthetically (visually) appealing properties when there is no need to under- stand the content. In contrast, for realistic material, aesthetic properties may become secondary to contextual features that determine the quantity and quality of information conveyed on a particular frame.

To investigate this question, Morrison et al. (1989) examined whether lower density formats would be favored in viewing realistic text presentations from an actual course. Results from two separate experiments reflected the opposite tendency: Subjects expressed preferences for higher density over lower density screens. The authors attributed this outcome to subjects’ concerns about increasing the amount of contextual support for the main ideas conveyed on individual text screens.

An important implication in comparing the Morrison et al. (1989) and Grabinger (1983) studies is that design principles supported using internally valid but artificial materials may have low ecological validity when applied to actual lessons.

Screen density 595

Nowever, because these two studies differed in several other key respects (e.g., o~ration~~ation of the density variable, nature of the preference assessment, type of learner) aside frum the realism of the stimulus material judged, unly indirect support is offered to support that conclusion. Resolution of this issue would be important for recommending to designers the desirable levels of density for text screens. In addition, for reseamhers, increased insight would be gained into possible differences in the way learners react to properties of artificial versus meaningful screen presentations.

The present study replicated and extended Morrison and colleagues’ (1989) design by varying the type of stimulus material presented (actual lesson, approximation-to-English (ATE), and nonsense notation) in conjunction with level of screen density and number of frames (individual vs. multiple) presented from a fixed lesson segment. The stimulus condition that presented actual tesson text on multiple frames represented a realistic context fur evaluating density preferences, whereas other ~ombina~ons represented varying levels of artificial (but also more controlled) contexts. Based on the Morrison et al. (1989) study about subjects’ needs for contextual support to facilitate information processing of text, it was hypothesized that as the realism of the text displays increased, preferences for higher density screens relative to lower density screens would increase, and vice versa, The basic rationale was that with realistic lesson material, contextual support would acquire greater saliency as a design feature relative to aesthetic properties.

Subjects were 32 graduate students (22 female and 10 male) enrolled in an instructional design course and 121 undergraduate students (109 female and 12 male) enrolled in an educational media course. Subjects within each education level group were randomly preassigned several weeks prior to the initiation of the study to two treatments, single frame and multiple frame. Because the single-frame soft- ware was developed first, the preassignment placed approximately 50% more subjects in that condition. Final ns were 92 in the single-frame condition and 61 in the multiple-frame condition. Subjects received credit toward their course grade for participating. In addition to the between-subjects variable of frame condition (single vs. rnul~~le)~ wi~in-subj~ts variables consisted of four screen density levels (22%, 26%, 318, and 53%) and three types of text (actual lesson, A-, and nonsense notation).

For assessing screen preferences, a paired-comparison design was employed involving a total of six unique pairings of the four density levels for each of the three text types. Specifically, subjects in the two frame condition groups (single and multiple) each viewed three sets of six paired-comparisons (one set per text type) for a total of 18 trials.

For example, a subject in the multiple screen conditions might view as the first set of six paired comparisons the six unique combinations of density levels for actual text (e.g., 31% vs. 26%, 3 1% vs. 22% 53% vs. 22%, 26% vs. 22%, 53% vs. 26%, 53% vs. 31%); this order would be random. The next set of six would be the same comparisons in a different random order for7 say% ATE. The third set of six would be a different random order of pairs fur RU~~WZ ~~~~~~o~.


For each of the paired comparisons, subjects were presented with two different screen density designs (of the same text type) and asked to indicate which one they would prefer in an actual lesson. Subjects completed all six judgments for an individual text type before beginning the next. Dependent variables were (a) the frequencies with which each density level selected and (b) the proportion of times higher density versus lower density screens were selected across trials.

Screen Displays

Materials for the actual lesson text condition were adopted from Morrison et al. (1988). These consisted of parallel text displays of statistics lesson content, presented in four different density levels. The stimulus material was devised beginning with a “core” frame in which print-page formatting conventions were basically followed (single spacing, and use of all spaces and lines, except between words and paragraphs, respectively). By counting all characters and dividing the sum by the total number of characters that the screen could display (total = 960), the density level of the core screen was determined to be 53% (see Figure 1, top left screen) (Tullis, 1983). The content of the 53% density screen was then divided at logical points into two, three, and four frames to produce average density levels of 31%, 26%, and 22%, respectively. The screen designs were based on the text available in a text-only environment such as the Apple II computers, MS-DOS computers using a text rather a graphical user interface (GUI), and mainframe text- based terminals.

/ VJhenwer possible, it is alwaysdesirable to report all three -sofoentraltendemy.n‘Ry providsdiffr3Ent~of infom~:?hemistiscore point attichtha distrtition bzilam!s.m?mIANisthe~repoint thatdivich thedistritution in hdf.!lh2MYXiSthShiCJhWt

fYxqmcy~~.Ingsneral,-, thC?lEatlp- mx3tuseful -0foentlal~bytawng intoa!3mntthethevalueofevery .!xxxe.

Pes h&red infivel sksahn fifclky histrc3plstrmashivlarn wbrki&igka wa. Allalid oflewhr oolt ho idr igalkW.t haosc:mtl aqx3gcnestAenear3tthi - lxchene dth&i5.1sms =sgidas alrcawhoit arllx!thm~ rsit amittw igu uepmi.Was hothi& [email protected]~Ug wrhm3 onthah folere dt.ststYmiliserindrdgvelotengeree cuatthsint~ WiffrcaxJnd pabv oohereqmindcmdslltwinwyovfh.

Figure 1. Sample screens using actual lesson text (top left), approximation-to-English text (bottom left), and nonsense text (top right).

Screen density 597

The ATE variations were constructed using Weaver’s (1949, pp. 42-44) “third order” ATE procedure in which randomly selected letters are substituted for actual letters in the text. The result is a presentation that maintains the same visual structure as natural language, but is free from meaning. An ATE presentation was derived to exactly match each of the four density variations in the actual lesson text set. Figure 1 (bottom left screen) shows the screen used for the 53% density level.

The third variation used Twyman’s (1981) nonsense notation in which X’s are used to represent conventional text and O’s and I’s to reflect variations such as color, inverse, headings, and unique styles. Relative to the ATE screen, this form was considered to have less resemblance to a meaningful text presentation (see Figure 1, top right).

Subjects in the single-frame condition were shown only the initial frame of the two or more frames that comprised the lower density presentations (i.e., 31%, 26%, and 22%). This procedure controlled the number of frames presented across density levels, while allowing the total amount of content viewed to vary. In contrast, subjects in the multiple-frame condition reviewed all lesson frames, thus control- ling the amount of content while allowing the number of frames to vary. The multiple-frame condition represents the real-life situation in which lower density presentations require additional frames to convey a fixed amount of content.

Each subject engaged in six-paired comparison trials representing all unique pairings of the four density levels for each of the three types of text (total = 18 trials). The order in which the text type sets were administered was determined at random. Instructions for the ATE and nonsense sets indicated that the frames would consist of “symbolic” notation used to depict a text presentation, but lack any meaning. The subjects were to “imagine” that actual lesson material was being conveyed. On all trials, the subjects were to indicate which design in the pair they would prefer to view in learning from a CBI lesson.

Procedure

From 2 to 10 subjects attended a given session. Each was seated at a terminal equipped with an Apple IIe microcomputer having a 12- or 13-in. monochrome screen, one or two 5 l/2-in. disk drives, and 128K of memory. The proctor began the session with a brief description of the purpose of the study (evaluate alternative CBI screen designs), followed by general instructions for responding. More specif- ic instructions involving the nature of the task and the computer interface were provided on introductory frames in the computer program. These instructions were only a few sentences per frame, consisting mainly of prompts and explanations; thus, text density was not a concern in their layout.

As previously described, the six screen comparisons within a text type set were presented in random order; the text type sets were also randomly sequenced. The density level randomly selected to be presented first in each comparison was labeled Design #I at the top of the frame, and the second density level was labeled Design #2. In the multiple-frame condition, the number of frames in the design and the particular frame being viewed were indicated in the lower left-hand corner (1 of 1, 2 of 3, etc.). A prompt in the lower right comer of the frame indicated that a key press would result in advancement to the next frame. After viewing both designs, subjects had the option of indicating their preference for one of the two designs or for reviewing either or both designs. Once a preference for a particular design was indicated, the next pair of designs was presented. At the completion of a set, an

598

insertion frame appeared indicating that a new set of comparisons would now be presented. The same procedures were then repeated for each of the remaining sets until all 18 paired-comparisons had been presented. Thus, the procedure permitted a review of each paired comparison during the given display trial, but not after that trial was completed (i.e., a new pair had been shown).

RESULTS

The proportions of subjects who selected different density levels in the paired comparisons are broken down by screen type and text type in Table 1. For example, when the 22% and 26% screens were paired in the single-frame screen actual lesson, .46 of the sample selected 22% screens, whereas 54 selected the 26% screen. As in Morrison et al. (1989), to obtain a clearer picture of overall preferences, Thurstone’s scaling procedure (Guilford, 1954) was used to represent the relative distances of the density selections on an interval scale created by (a) converting the proportion values (Table 1) into normal curve deviates, (b) averaging the deviates for each stimulus to produce an overall mean, and (c) adding the absolute value of the largest negative mean to each of the means to preclude negative values on the final scale (i.e., the least preferred stimulus will have a final mean of zero). Figure 2 provides a graphical representation of the scales for each Screen Type x Text Type condition.

As may be seen in the figure and table, preferences were less varied for actual lesson text than for other text forms, but tended to favor higher over lower density levels. With the two artificial text forms, medium density levels were most favored, whereas the highest (53%) level was least favored. To analyze statistically whether differential preferences were indicated, tabulations were made of the total number of times each density level was chosen by subjects out of the three times it appeared in the six paired comparisons for a text-type set. Possible scores therefore ranged from 0 to 6. The resultant means are summarized in Table 2. Given the interdependency of the density selection scores for a given paired-comparison set, a Friedman analysis of variance (ANOVA) by ranks, a nonparametric test, was used to compare their ordinal rankings within subjects for each text type by screen type combination (a total of six tests). Findings were significant in two cases: ATE text with single screens, X2(3) = 10.15, p < .02, and actual lesson text with multiple

Table 1. Proportion of Selections for Each Density Level on Screen Type x Text Type Paired-Comparison Trials

Comparisons

Screen and Text 22126 22f31 22153 26131 26153 31153

Single Screens Actual Lesson ATE Nonsense

~ultjple Screens Actual Lesson ATE Nonsense

.46/.54 43f.57 .50/.50 .55/*44 .41/.59 52l.48

.461.52 .451.55 .51/.49 .52/.48 .60/.40 .70/.30

.46/.52 .54/M .53i.47 .49/.51 .61/.3Q .611.39

.31/.69 34f.66 461.62 MU.52 .53/.47 .46/.54

.381.62 .431.57 .511.49 .431.57 Xv.41 .62J.38

.41/.59 511.49 .511.49 .49/.51 561.44 .59/.41

Note. ATE = approximation to English.

Screen density 599

Actual Lesson 1 Actual Lesson 31%

22% 26%509/o f

=m 0 .l 2 .3 .4 s 0 .1 2 3 .4 .5

Approximation to English

50% 22% 26% 31%

1 0 .l 2 .3 .4 .5

Nonsense

Approximation to English

0 .l 2 3 .4 6

Nonsense

50%22% 31%26%

a cs 0 .l 2 .3 .4 5

Figure 2. Thurstone Scales for single-screen (left group) and multiple-screen (right group) conditions.

screens, X2(3) = 8.99, p c .03. In the former case, the 53% level tended to be least preferred and the 31% level most preferred (see Table 2); in the latter case, the 22% level was least preferred and the 26% level most preferred. It should be noted that the six tests conducted, each using an alpha of .05, inflate the family-wise error, or the chances of one or more Type I errors occuring, to approximately .26. Thus, these results need to be viewed cautiously.

To substantiate these results, given the conservative nature of the above nonparametric tests, repeated-measures ANOVAs were conducted comparing density selection frequencies (see means in Table 2) for each Text Type x Screen Type cell. These analyses also permitted appropriate followup testing of individual pairs of means, with the Type I error rate controlled. Results were similar to those of the Friedman ANOVA. For the single-frame group, a significant density level effect was again shown for the ATE text, F(3, 273) = 3.72, MS, = 1.39, p c .Ol. Follow-up Tukey honestly sig~ficant difference (HSD) tests showed that the 53% density level mean was signi~c~dy lower than both the 31% and the 26% density levels. For the multiple-frame condition, the ANOVA was significant for ATE text, F(3, 180) = 2.62, MS, = 1.38, p < .05, and also for regular lesson text, F(3, 180) = 2.92, MS, = 1.34, p < .04. The follow-up tests for ATE text showed no differences between density levels, although the difference between 53% density, the lowest mean (M = 1.28), and 31% density, the highest mean (Zt4 = 1.77), approached significance (p < .06). For actual lesson text, the only significant difference (p e .05) reflected a lower preference for the 22% level (M = 1.13) than for the 26% level (M = 1.69).

As in Morrison et al. (1989), an additional set of analyses was performed to determine whether the higher or the lower density display tended to be selected more frequendy across pared-comp~son trials. To test this, we tabulated the total frequencies of higher density choices and lower density choices made by all subjects across the six trials for each Text Type x Screen Type combination. For example, if on the pairing of the 26% level with the 31% level the subject selected the 3 1% level, that response would have been tabulated as a higher density selection.

Screen density 601

expository text in CBI lessons. The research issue concerns the implications of using realistic versus artificial materials to conduct experiments on variables relating to the design and delivery of CBI. We will turn to ins~ctional design implications first.

Although the present results do not address degree of learning from different density presentations, they directly support Morrison and colleagues’ (1989) find- ing that adult learners prefer middle and high density text screens over low density screens when viewing actual lesson materials. Specifically, learners were indicating preferences for the types of screens that they felt would best help them learn instructional material. Previous studies have suggested that learner selections of contextual properties of CBI displays (as opposed to substantive properties affecting what is actually taught) tend to be consonant with their needs and predictive of higher performances (see Ross & Morrison, 1989). If one is familiar with the early research and intuitively supported design guidelines (Grabinger, 1983; Heines, 1984; Hooper & Hanna~n, 1986), this outcome may at first appear surprising. That is, since computer screens can hold less info~ation than textbook pages, it may be taken for granted that restricting the amount of content presented, through such conventions as double spacing, wide margins, and increased white space, is desirable for increasing the readability and attractiveness of text screen displays. Further, there is evidence from human factors studies that error rates increase as the density of information on computer screens increases (Danchak, 1976; Smith, 1980, 1981, 1982). Reading data from information displays, however, involves very different processing demands than does trying to comprehend expository text. Media attributes and task attributes thus need to be differentiated (Clark, 1983; Ross & Morrison, 1989). Seemingly, fund~ental principles of how text should be written and formatted to promote comprehension should apply in much the same way to all media that incorporate text. Refinements in the generally pre- scribed text designs can then be made to accommodate unique media attributes. CBI presentations, for example, would be expected to include special attentional and interactive features that increase motivation (Keller & Suyuki, 1988) and engagement between the learner and the lesson content (Hannafin, 1989; Hannafin & Hooper, 1989).

Two explanations are suggested for why the higher density screens were preferred with actual lesson text. First, from an information-processing perspective, higher density screens tend to increase proximal contextual support for information by presenting main ideas and supporting explanations in the same frame. This find- ing is similar to the conclusion drawn by ~illingh~ (1988) regarding screen design and text structure. Second, a higher density screen means that fewer frames will be required to present the same amount of material. “Lesson navigation” (Ham&in & Hooper, 1989; Soulier, 1988) should become easier as a result of the reduction in frames. The implication for designers is that, although aesthetics are clearly important, the key consideration in text screen design is analysis of content to maximize comprehension of the information presented on the given frame. As Hannafin and Hooper (1989) indicate:

A single detailed screen that helps to contrast critical differences between examples and nonexampks during a concept learning task may be more effective than several, spacious screens that fail to illustrate important relational differences effectively. It is not adherence to superficial rules that will advance the science of screen design but greater attention to the task attributes and processing capabilities of learners. (p. 157)


Computers using a GUI such as an MS-DOS window environment or Apple Macintosh introduce additional variables and concerns. While it is still possible to design a screen using a proportional font with finer variations in leading of densities similar to those used in the present study, the possibility of scrolling text fields raises new issues. A field could be sized to present the different density levels of text in one “frame” and allow the learner to scroll through the text. A question aris- es then as to whether the learner would prefer the scrolling capability of one frame with 26% density being displayed, or having the information on three frames with no scrolling.

A second issue addressed by the present research is the relative advantages of using realistic as opposed to artificial stimulus materials in conducting ins~ctional technology research. Through the use of artificial materials, high internal validity is gained by eliminating, as confounding variables, subjects’ prior experience with materials and associated reactions to their meaning. At the same time, external validity is reduced by the lack of similarity of the learning conditions to what is likely to occur in practice.

In reference to the present design, had we manipulated only the artificial materials (ATE and nonsense notation) to achieve high internal control, our results would have favored lower density over higher density screen designs. This outcome would have supported one of Grabinger’s (1983) factors, established with nonsense stimuli, supporting “spacier” design formats. As Ross and Morrison (1989) sug- gest, the interaction of medium and method in instructional technology studies is of direct interest as a research outcome rather than an unw~ted source of error variance. When the present subjects viewed realistic lesson material, their decisions about the desirability of the different screen density levels were presumably influ- enced by perceptions of which presentations would make the material easier to comprehend and the CBI lesson easier to use. In contrast, when examining frames containing nonsense text, aesthetic properties were likely to become more salient in the absence of any cues relating to comprehension or meaning. Consequently, selecting a low density ATE or nonsense frame offered the advantages of a spacier, potentially more readable, presentation, without the concomitant real-life disadvan- tages of a reduced informational context and an increased number of lesson frames. Although artificial stimuli are of value for establishing principles of learning in basic educational psychology research, only by using ecologically valid materials can the educational technology researcher determine how presen~tional variables interact with media attributes to influence learning from actual lessons.

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Documents

Preferences for different CBI text screen designs based on the density level and realism of the lesson content viewed