metaphor in visual displays designed to guide action

This article was downloaded by: [University of Kiel]On: 25 October 2014, At: 09:31Publisher: RoutledgeInforma Ltd Registered in England and Wales Registered Number: 1072954 Registeredoffice: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK

Metaphor and Symbolic ActivityPublication details, including instructions for authors and subscriptioninformation:http://www.tandfonline.com/loi/hmet19

Metaphor in Visual Displays Designed toGuide ActionCathy H. Dent-Read , Gary Klein & Robert EgglestonPublished online: 17 Nov 2009.

To cite this article: Cathy H. Dent-Read , Gary Klein & Robert Eggleston (1994) Metaphor in VisualDisplays Designed to Guide Action, Metaphor and Symbolic Activity, 9:3, 211-232, DOI: 10.1207/s15327868ms0903_4

To link to this article: http://dx.doi.org/10.1207/s15327868ms0903_4

PLEASE SCROLL DOWN FOR ARTICLE

Taylor & Francis makes every effort to ensure the accuracy of all the information (the“Content”) contained in the publications on our platform. However, Taylor & Francis, ouragents, and our licensors make no representations or warranties whatsoever as to theaccuracy, completeness, or suitability for any purpose of the Content. Any opinions andviews expressed in this publication are the opinions and views of the authors, and are notthe views of or endorsed by Taylor & Francis. The accuracy of the Content should not berelied upon and should be independently verified with primary sources of information. Taylorand Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs,expenses, damages, and other liabilities whatsoever or howsoever caused arising directly orindirectly in connection with, in relation to or arising out of the use of the Content.

This article may be used for research, teaching, and private study purposes. Any substantialor systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply,or distribution in any form to anyone is expressly forbidden. Terms & Conditions of accessand use can be found at http://www.tandfonline.com/page/terms-and-conditions

http://www.tandfonline.com/loi/hmet19

http://www.tandfonline.com/action/showCitFormats?doi=10.1207/s15327868ms0903_4

http://www.tandfonline.com/action/showCitFormats?doi=10.1207/s15327868ms0903_4

http://dx.doi.org/10.1207/s15327868ms0903_4

http://www.tandfonline.com/page/terms-and-conditions

METAPHOR AND SYMBOLIC ACTIVITY 9(3), 21 1-232 Copyright O 1994, Lawrence Erlbaum Associates, Inc.

Metaphor in Visual Displays Designed to Guide Action

Cathy H. Dent-Read Miami University (Oxford, Ohio)

Gary Klein Klein Associates

Robert Eggleston AFWAL/HEA Wright Patterson Air Ebrce Base

We report a naturalistic study of how metaphor is used in visual displays designed to guide action in chemical process control, flight training, and flight environments. Our research question is whether pictorial metaphor is used to organize information that could be used to guide skilled action. Pictorial metaphor has been analyzed in art and cartoons, but such depictions are not used in adapting action to ongoing events. In pictorial metaphor, an object or action is depicted in terms of a different kind of object to which it bears a resemblance (e.g., a flight path depicted as a highway). Such depiction is potentially important in guiding skilled action under time pressure because the familiar can be used to guide attention to important aspects of ongoing events. We interviewed 20 designers regarding pictorial designs that they had found most challenging. We found that most pictorial metaphors occurred in flight designs. Pictorial metaphors are described for each type of design and analyzed in terms of affordances (i.e., what actions the metaphoric object affords also required in the ongoing event). The results show that pictorial metaphor is currently in use in computer-generated displays and that such metaphors effectively direct attention to real-world information needed to guide skilled action.

Is there a highway in the sky? No, but depicting one for a pilot that corresponds to a safe path for a jet plane may enhance the pilot's ability to fly the

Requests for reprints should be sent to Cathy H. Dent-Read, Center for the Ecological Study of Perception and Action, Department of Psychology, U-20, University of Connecticut, Storrs,

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

21 2 DENT-READ, KLEIN, EGGLESTON

aircraft. A depicted highway in this situation is a visual metaphor (i.e., a depicted highway for the driver of a car would be literal). The topic of the metaphor is the flight path and the vehicle is the highway; the flight path is depicted in terms of the highway because the two resemble each other in form and function. Metaphors may be very effective in organizing information, and the question of this study is whether pictorial metaphors occur in displays designed to guide action in the world, such as controlling a chemical process or flying a jet aircraft. Pictorial metaphors are potentially useful in attuning the perceiver to the aspects of the environment that could support skilled action (see Fowler & Turvey, 1978, for a treatment of skill acquisition as attunement). For example, seeing the flight path as a highway not only directs flight accurately in forward and lateral directions, it also indicates optimal altitude by suggesting that the pilot not fly into the solid surface depicted in the highway. In this introduction, we discuss how visual displays are structured, how metaphors have been used in display design, and we offer both a definition of metaphor and a theoretical foundation for its use in designing displays.

The concept of metaphor in design has been mentioned in the popular literature (Carroll, 1983), although a close specification of the definition and properties of metaphor and its usefulness in display design has been lacking. Such an analysis of pictorial metaphor in art (Aldrich, 1968, 1971) and in drawings (Kennedy, 1982), however, has been performed. Pictorial metaphor is defined as depicting an object in terms of a different kind of object to which it bears a resemblance (e.g., mountains depicted as rooftops). This article explores whether such visual metaphors are used in displays intended to guide skilled action and decision, rather than to provide aesthetic experience.

People who operate complex machines (e.g., jet aircraft and nuclear power plants) require detailed and complex information about the current situation to perform their tasks. The situations of chemical process control and flight are dynamic and complicated and pose a challenge to designers who con- struct instruments and displays that allow the operators to perform their tasks. The display must present dynamic information that is specific to actual surfaces in the world so that an operator can use the display to guide adaptive action in complex, dynamic, and often time-limited situations. Metaphor guides attention in an immediate way (Verbrugge, 1980), so this tool may be in use in situations where action is highly skilled and requires close attention to key information in the environment. Metaphor can guide attention to the resources available, offer a framework for viewing a situation, and provide a focus of interpretation. The "wordprocessor as typewriter" metaphor, for example, leads the user to notice resources for creating text, aids the user in seeing the task in terms of an activity that is well known, and provides a focus for interpreting the effects of different commands. The importance of organization in display design has been recognized (Easterby, 1967), and new

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

METAPHOR IN VISUAL DISPLAYS 21 3

display technologies make systems of organization even more important. The major question of the present study is whether metaphors are used in visual displays that are designed to guide skilled action.

Metaphor is a potentially powerful tool for guiding attention by referring to what is well known and familiar and by commenting on or depicting what is less well known. With an increase in the use of pictorial displays presented by cathode-ray tube (CRT) comes more opportunities for visual metaphor. Indeed, metaphors are pervasive in designs for interfaces in the areas of word processing and animation (Carroll & Mack, 1985). Organizing metaphors that structure a whole display or set of displays and visual metaphors that can appear in iconic (i.e., pictorial) displays seem to be important tools that designers draw on in developing word-processing software and pictorial displays. Metaphor, in addition, has been a powerful tool in training and teaching skilled action to aid learners in smoothly performing such actions as playing tennis, an action in which a forehand swing is described as being like "shoving a pie in someone's face" (Klein, 1978). The metaphor draws attention to resemblances; a useful metaphor emphasizes relevant likenesses (Dent, 1987a; Verbrugge, 1980; Verbrugge & McCarrell, 1977). Such a metaphor emphasizes aspects of a situation that are relevant to action or inference or both (Klein, 1987).

Are designers of pictorial displays that are meant to guide action taking advantage of metaphor? One of designers' overall tasks is to create displays that will support user awareness of the real-world situation that the display is about and especially of the action possibilities open to the user. These action possibilities are some of the affordances of the situation (Gibson, 1979). We consider whether metaphor is used in displays to clarify the affordances for action. Displays must aid users in knowing which actions could and should be performed in a given situation. This study investigates the use of metaphor in designs that guide action by collecting information on the process of designing displays for chemical process plants and jet aircraft and by examining the designs for the use of metaphor. To analyze displays for visual metaphor, a definition of metaphor and a theoretical foundation for the use of metaphor as part of a visual representation are required.

DEFINITION OF METAPHOR

The definition of metaphor is a point of controversy in philosophy and literature (Black, 1962; Johnson, 1981), cognitive psychology (Ortony, 1979; Verbrugge, 1980), and human-computer interaction (Carroll & Mack, 1985). The analyses that are most germane to this study are those that make explicit the relation between verbal and nonverbal metaphor (Dent, 1987a, 1987b, 1990; Dent & Rosenberg, 1990; Dent-Read & Szokolszky, 1993;

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Kennedy, 1990; Verbrugge, 1980), and those that relate metaphor explicitly to computer interfaces and design (Carroll & Mack, 1985). In the latter category, Carroll and Mack (1985) distinguished between theories of opera- tional metaphor that concentrate on metaphoric thought, theories of struc- tural metaphors that are formal theories aimed at the mechanism of using metaphor in thought and language, and pragmatic theories of metaphor that analyze metaphors used in the course of attaining a goal. The category of pragmatic theories of metaphor is used in this study of the actual use of metaphor by designers.

To accomplish this study, a definition of metaphor and a dear understanding of the relations of verbal and nonverbal metaphor are necessary. A relatively recent development in psychological metaphor studies concerns work on pictorial or nonverbal metaphor that emphasizes its perceptual basis and the idea that metaphor goes beyond language (Dent, 1987a, 1990; Dent & Rosenberg, 1990; Kennedy, 1982, 1990; Verbrugge, 1980; Verbrugge & McCarrell, 1977). This work supports analyses of metaphor in nonverbal domains (e.g., pictorial displays) and provides the starting point for our definition of verbal and nonverbal metaphor. If pictorial metaphors are found in displays used in naturally occurring situations, arguments that metaphor is a purely linguistic phenomenon (Olson, 1988) will require modi- fication.

In a novel, verbal metaphor one thing is said to be, or be like, another kind of thing to which it bears a resemblance. This resemblance can be based on various aspects that are invariant across objects or events, for example, style of motion (e.g., a whale spouting and a geyser), process (e.g., water drawn up through tree trunks and straws), surface layout (e.g., snow on a tree and a blanket around a person), or affordance (e.g., current of air and current of water as paths of locomotion). In using a metaphor, the speaker is referring to one thing in order to talk about another and the hypothesized mental activity is thinking of one thing in terms of another. The topic, or what the metaphor is about, is seen in the light of or seen through theJilter ofj the vehicle, or the word being used figuratively (Black, 1962, 1977). These word and object relations are diagrammed in Figure 1, where the simultaneous reference of the figurative word or phrase to both its literal referent and its temporary figurative referent is depicted.

In pictorial metaphor, one thing is depicted in terms of another thing that is different in kind, but that bears a resemblance to the first object. As with verbal metaphor, the resemblance can be across different aspects of objects or events. All the examples given here can be presented as pictorial metaphors; a whale could be depicted with a geyser coming from its head, and the path in the air for a plane could be depicted as a highway. Clearly process and function, not just shape, can be the basis of pictorial metaphors. Some properties of the vehicle object must be present in the depiction of the topic

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


TOPIC OBJECT RESEMBLES VEHICLE OBJECT

OR EVENT < OR EVENT

REFERS TO I REFERS TO

TOPIC PHRASE <I VEHICLE PHRASE COMMENTS

FIGURE 1 Sign relations in verbal metaphor.

TOPIC OBJECT RESEMBLES VEHICLE OBJECT OREVENT < OREVENT

TOPIC DEPICTION VEHICLE DEPICTION

FIGURE 2 Sign relations in pictorial metaphor.

object in order for the depiction to be metaphoric. These relations are illus- trated in Figure 2, which shows that the structure of pictorial or visual metaphor is the same as that of verbal metaphor, although no words are used in the case of pictorial metaphor.

Some uses of language may have originated as metaphors, but current use is literal; these are called frozen, or dead, as opposed to novel, or live metaphors. In frozen metaphors such as "the leg of the table" or "wedded to work, " one term does have two meanings (e.g., leg as limb and leg as part of furniture), but only one meaning is used at a time. To call a cursor a hook is an example of a frozen metaphor because no aspects of hooking or catching are used in the display. An example of the analog to verbal frozen metaphors in the pictorial mode is the color red used in nuclear power station displays to mean in operation, or hot. Red has other meanings-"stop" (at traffic lights) or "warning of emergency" (e.g., red lights on ambulances), but these meanings are not intended by the designers of the power station operator displays.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Metaphor and analogy are not synonymous; analogies consist of parallels in relations. For example, in the analogy "kittens are to cats as puppies are to dogs" the same relation of offspring to parents exists for both sets of objects. In this example, the objects are all of the same kind so the analogy is literal (Ortony, 1975). When the two sets of objects are not the same kind of thing, (e.g., interactive software and conversation) then the analogy is metaphoric. In this case, the analogy would be "interactive software is to the computer as conversation is to people. " Verbal metaphors and pictorial metaphors could be used when referring to the relations in many metaphoric analogies.

REPRESENTATION IN DISPLAYS

To show how to identify metaphors in displays, it is necessary to discuss the different types of signs or representations in displays and then to show which of these is metaphoric. As with defining metaphor, defining and classifying signs and representations is an ongoing process. C. S. Peirce (1960) has provided the most detailed and systematic theory of signs, one which explicitly deals with the relation of a sign to what it stands for, of a sign to the perceiver of the sign, and of the perceiver to the object that the sign stands for. Therefore, this system relates verbal and nonverbal as well as pragmatic aspects of signs, providing the best basis for analyzing computer-generated displays. Research on sound aspects of computer interfaces has made use of a simplified version of Peirce's system (Gaver, 1986), although the following, more detailed, version fits metaphor into the overall pattern of types of signs more accurately.

An object can represent something (i.e., be a sign for that thing) by means of the relation between sign and thing (this relation is the ground) in three ways: (a) based on a likeness to the thing the sign represents, (b) because of a causal connection between the sign and thing, or (c) based on a conventional social rule that relates sign and thing. In the first case, in which a sign has a likeness to the thing it stands for, the sign is iconic. The horizon line in a cockpit CRT display is iconic. The second type concerns signs that represent their object on the basis of a causal connection; these are indexical signs. A fuel gauge indicates the level of fuel, and is causally connected with it. Finally, some signs have conventional aspects. For example, a gauge with zero on the left and some positive amount on the right exemplifies a convention; it is a convention to place zero on the left and the positive amount on the right.

Because some iconic signs are metaphors, we examine that type of sign in detail. There are three types of iconic signs. The first is based on simple qualities such as color and one-to-one correspondence of points and is called

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


image; colors and photographs are examples. The second represents the parts of one thing by analogous relations in their own parts and is called a diagram. A flow diagram of electric circuits is an example. The third consists of an icon that is both a sign of something and, also, represents something else because of a parallelism between the two things being represented; this third case is metaphor. Therefore, in a metaphor, whether verbal or pictorial, the vehicle is a sign of one thing independently of its role in the metaphor and is also a sign of a second thing in its role as a vehicle. For example, the corridor in a flight display is a sign of a real corridor (or highway) and is simultaneously a sign of the flight path of the plane in the sky. Therefore, it is functioning as a pictorial metaphor. The flight path depiction can function this way because of a parallelism between corridors or highways and flight paths. Note that parallelism implies two critical factors: (a) the two things that the vehicle is a sign of are from different domains (or they could not be parallel) and (b) there is some resemblance between them (the aspects that are parallel).

Given that metaphor can organize a pictorial representation to provide immediate awareness of some aspect of the world, and given the previous specifications of metaphor and pictorial representation, actual display designs can be analyzed for the presence of metaphor. The goals of this analysis are to perform a naturalistic study of whether and how metaphor is used in designing displays.

METHOD

Participants

Twenty display designers participated in the study. Designers were chosen who worked on CRT displays (primarily pictorial) for cockpits of jet airplanes and control rooms in chemical plants. Some of the designers had been involved in revisions of existing designs; some were working on designs for future stations. The number of years of experience ranged from 5 to 26 with an average of 14, and the number of designs worked on ranged from 6 to 48 with an average of 24. One had no college degrees, 3 had bachelor's degrees (in engineering or psychology), 10 had master's degrees (in engineering, psychology, or business), and 6 had doctoral degrees (in engineering or psychology). Eleven were employed by the military; 9 were working in private industry.

Materials

The designers were interviewed using an adaptation of the Critical Decision Interview (Flanagan, 1954; Klein, Caldenvood, & Clinton-Cirocco, 1986). Because our goal was to elicit information about the form and function of

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


designs, and the process of developing the designs, we focused not on critical decisions but rather on displays the designers found particularly challenging. An example of an interview summarized in standard form is given in Appen- dix A (the designer is not named to maintain anonymity). The material covered in the standard form was covered in each interview, although not necessarily in the order it is presented in the standard form.

Procedure

The study was conducted in three phases. In the first phase, designers were identified and asked if they would be willing to be interviewed. None declined to be interviewed. Seventeen interviews were conducted; in three cases, two designers were interviewed together. Fifteen interviews were conducted by Cathy Dent-Read and a second person; for 14 of the interviews, the second interviewer had design experience and for 2 of the interviews, the second person had human factors experience. Two interviews were conducted by Cathy Dent-Read alone; and one by two other interviewers.

The introduction to the interview consisted of a statement of our interest in display formats that present information about the real world that the operator needs in order to act or make decisions; it stated that we were particularly interested in cases in which a real-world object was depicted that was not literally in the situation. The example used was the fight path of a plane depicted as a corridor or highway. Corridors and highways exist, but not in the sky; yet, the depiction helps the pilot or the designer.

The next step in the interview was to ask the designer to pick a design that had been particularly challenging or unique in some way and to explain that design and its development. Examples of the designs chosen are given in Appendix B. From there, the interview followed the topics introduced by the designers, with the interviewers probing for detailed information of the design itself, the ideas behind it, and the history of different elements in the design. In addition, the tasks that the design was made to support were discussed in detail. The interviewers always probed for designs that had been thought of or tried but not used, and for information as to why these alternative designs were not optimal. All but three interviews were tape- recorded.

The interviews were written based on notes and tape recordings so that each included the names of interviewees and interviewers; biographical data on the designer or designers; and, for each different design discussed, information on the design problem, unique or challenging aspects of the problem, the solution (i.e., the design), alternatives considered but not used, and evaluation of the design. Supporting figures and text were obtained on the designs when possible.

Interviews began with the following statement from the main interviewer:

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


We are interested in the kinds of decisions you made in formulating the problem and in evolving the display. We need to find out what pilot functions the display is supposed to support, that is, what situation awareness did you have to inculcate in the pilot, how information about the real world is retained in the display, how you chose to represent that information, and what information was not included and why. We are especially interested in aspects of a display where a real object is depicted that is not in the real situation. For example, a corridor is sometimes depicted for the plane to fly in; there is no real corridor but it helps the pilot and the designer to think of it that way and see it that way on the CRT. We will provide you with the report in six to eight months which will contain ideas used by several designers and you may find some of these useful, we may be able to facilitate exchange of ideas among designers.

The interviewer then obtained information on the personal history of the design engineer, including any special training, changes in company, job functions, and the number of designs worked on. Finally, the interviewer asked the interviewee to choose the most recent point in his or her work in which a display format decision was made on a problem that was particularly challenging and unique. The interviewer asked about metaphors in the designs by saying:

We are interested in how you selected symbols, placed them, had them move, and what the goals were. We are especially interested in the symbols chosen and how one thing can be used to think about another, like the corridor being used to think about the pathway of a plane. We might call these double symbols because they stand for two different real things at the same time. What double symbols help you describe the pilot's task? What double symbols help you to design a display that works?

For each design problem chosen, the designer was asked to describe design goal (i.e., user task, goal for display, and context of use; e.g., nighttime), the problem or challenge that was involved, the chosen display format and why it was chosen, implementation, and outcome (e.g., what worked in rapid prototyping and what did not). The designers were also asked about what other possibilities he or she considered and why they were rejected.

The second phase of the project consisted of asking experts on metaphor to identify any metaphoric aspects of the designs and, especially, any organizing metaphors that were being used by the designers. Two linguists and two psychologists, who researched topics in metaphor, were sent summaries of the first 10 interviews (13 designers, 15 designs) and were asked to identify any root, or organizing metaphors analogous to the desktop metaphor used for designing word processing displays, and to identify any parts of the designs that were metaphoric. We did not provide definitions of metaphor, but asked the experts to state their own definitions. The experts were told that

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

220 DENT-READ, KLEIN, EGGLESTON

our overall goals were to arrive at a clear and concise definition of metaphor, a delineation of metaphor in the designs, and a statement of how metaphor may be useful in guiding designers.

The third phase consisted of synthesizing the experts' reports and clarify- ing empirical questions, as well as discussing methods for investigating these questions. In this phase, the four reports obtained from experts were sent to two additional experts, and to one of the original experts along with five more interviews that had been collected in the interim. To obtain a higher level analysis, we asked these experts to synthesize the different analyses of what was metaphoric about the designs and to locate any organizing metaphors that were used. We then had on-site meetings to receive their reports. In addition to the above directives, the following specific questions were discussed: (a) What is the definition of metaphoric design or design element and how is such an element identified?, (b) How can different design goals be reconciled in single designs or sets of designs?, (c) Are there levels of metaphors in designs, that is, some very general metaphors that may be used for organization but never appear directly in the design and less general ones that actually appear?

Transcription and Scoring

The first 10 interviews were scored for verbal metaphors referring to elements of displays, pictorial metaphors in the displays, organizing metaphors in the displays, and verbal metaphors describing the process of designing the displays. These four categories of metaphor were identified from expert reports on the interviews. Two independent judges agreed on 94% of the occurrences of these types of metaphor. The data from one or the other judge, determined randomly, was used in the cases of disagreement.

RESULTS AND DISCUSSION

The 17 interviews resulted in detailed descriptions of 32 designs. The designs that illustrate noteworthy aspects of metaphor are given in Appendix B, numbered for reference. The designs were categorized into four types based on the general context in which the display occurs: (a) control station-two chemical process plants (one planned but not executed), two missile warning stations, one nuclear power plant; (b) flight training-one instructor operator stations, four simulator designs; (c) flight and surveillance-18 jets (one planned but not executed), three helicopters, and one patrol plane; and (d) metaphors for the process of designing itself.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

TABLE 1 Frequencies of Different Types of Metaphors Used by Designers

Type of Metaphor

Descriptive Pictorial Organizing Process

Type of Display Total M Range Total M Range Total M Range Total M Range

Control station 8 1.6 2-6 4 0.8 0-2 1 0.3 0-1 0 0 -

Simulator 6 1.2 0-6 4 0.8 0-4 0 0 0 0 0 - Flight 48 2.3 0-22 19 0.9 0-7 2 0.1 0-2 2 0.1 0-1 Surveillance 2 2 - 0 0 - 0 0 0 0 0 0

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Metaphors in Displays

Frequencies for the different types of metaphor are given in Table 1. First, designers used verbal metaphors, called descriptive metaphors, in referring to and describing the displays and how the displays work. Examples of this are: a cursor is called a "tadpole, " text is said to "scroll, " masking radar ranges are called "shells. " Some of these metaphors were accurate descriptions of the depiction in the display and the function of what was depicted (e.g., the masking radar referred to as a "she1l"drawing on the protective function and the shape of the range; the limits of a gun fired from one plane at another were described saying it was like "squirting a hose" at the enemy plane (#4, see Appendix B). In other verbal metaphors, the metaphoric term did not seem related to the function of the referent, for example, a cursor that was a circle with a vector was called a tadpole; in this case, the cursor did not move or function like a tadpole. All but one designer used verbal metaphor, the exception was the description of color used in displays for the instructor operator stations (#3).

Second, metaphors were used in the display depiction itself, that is, pictorial metaphor was used. The two major uses of pictorial metaphor were depicting the flight path of aircraft as a corridor or highway and depicting the ranges of electromagnetic radar as surfaces. In addition, in one suggested design (#8), safe areas for flight close to the terrain were depicted as ponds of varying depths. These are pictorial, or visual metaphors. These metaphors are important because they demonstrate that metaphor is used in display depictions. In crew station displays, pictorial metaphors are used to show safe areas, the highway or ponds, and areas of danger, the radar ranges of ground based weapons and the tracking radar of other aircraft. In the case of tracking radar of the other aircraft, lines and color are used in the depiction to stand for solid surfaces and simultaneously for radar ranges that are not solid surfaces. In operator stations, generalized paths, as opposed to a specific type of path like the highway or corridor, are used as pictorial metaphors for missile vectors and chemical processes.

In both the "radar as solid surface" metaphor and the 'pight path as highway"metaphor, the affordances (Gibson, 1979) of the object used metaphorically in the depiction (the solid surface or highway) are the same as the affordances in natural situations. Solid surfaces do not afford flying through and radar is to be avoided; highways afford smooth and accurate forward motion in a vehicle and the flight path is the best path forward in the aircraft. Such invariance of affordances across topic and vehicle referents may be critical for a successful pictorial metaphor in displays that guide action. Action guided by such displays has real consequences; flying into enemy radar range is dangerous, as is flying into a solid surface. The idea of affordances as specific properties of substances and surfaces taken with reference

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

METAPHOR IN VISUAL DISPLAYS 223

to an animal, that is, what the environment provides animals that are com- patible with it, provides a powerful way of analyzing the ground of visual metaphors in these types of displays.

Third, the designer thinks of some aspect of the plane or of the mission metaphorically and talks about it that way. An example is describing the functioning of the plane in terms of health, with the hydraulic system parallel to the circulatory system, monitoring status as examination and diagnosis, responses to emergencies as remedies, and the like. This thinking was not used in the design of the formats themselves, but in designing possible organi- zations of status display formats. This is an example of an organizing metaphor; such metaphors function to structure a whole set of decisions about what should be portrayed and how it should be portrayed.

Organizing metaphors function to guide decisions within individual displays as well as about sets of displays. A second example that illustrates these aspects of organizing metaphors, the display designed by the Navy (#7), is based on thinking of flying solo as flying in formation, that is, depicting a phantom plane that the pilot treats as a wing leader with that plane showing acceleration, turning, deceleration, landing gear, and the like. This thinking directly affected the display in that a depiction of a plane is used as the sign to guide flying. The depiction of the plane is not metaphoric because it only stands for one thing-another plane. However, the activity of the pilot is not really flying in formation so the depiction of the plane is evoking an organization for the pilot. Thus, in addition to structuring design decisions, organizing metaphors provide structure for the user. An organizing metaphor can show the user where to look for certain variables, and the user will know how variables will be depicted because the different components are inherent in the metaphor, for example, in 'tfollowing aflight path as Pying in formation. "

Organizing metaphors always result in verbal metaphors when designs are described; the metaphor organizes talk about designs as well as the designs themselves. The idea that organizing metaphors structure discourse has been proposed based on examples from natural language, such as the cluster of descriptions we use for arguments or debates that relate them to wars (John- son, 1987; Lakoff, 1987; Lakoff & Johnson, 1980). Whereas the examples of descriptions used previously were of frozen metaphors (e.g., "he beat me in the debate"), our study revealed that organizing metaphors structure both novel and frozen metaphors.

The fourth type of metaphor concerned the description of the design process itself. One designer said designing a display is like trying to paint the Mona Lisa-you can try, but the final product will not be anywhere close to what you try for. A second designer said the process is like putting together Chinese puzzles-you fit many pieces together, then add one more piece and the whole thing falls apart.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Pictorial and Organizing Metaphors in Different Types of Displays

Operator station displays showed a minimal use of pictorial metaphor and organizing metaphor. These displays either were primarily diagrams of the tanks or containers, valves, flows, and the like or primarily indexical displays, that is, grids, graphs, or rows of numbers. All made use of color (i.e., image likenesses or based on conventions). One pictorial metaphor used was a chemical change portrayed as a path on which temperatures "march" as the reaction takes place; a second was the path of missiles portrayed as a surface along which the missile progresses (#I). A second pictorial metaphor concerned the radar range of satellites and ground-based detectors portrayed using lines that stood for the edges of surfaces; that is, portrayed as surfaces (#2). Pathways and other types of surfaces used metaphorically will be discussed in more detail in relation to the designs for future cockpits. The interactive display for the missile warning station was talked about in terms of the 'keography" of placing displays on the screen and in terms of the operator having a "dialogue" with the display, although neither of these potential organizing metaphors was used systematically. To use them systematically, designers would have had to use maps, quadrants, boundaries, and the like for the geography metaphor and rules of conversation for the dialogue metaphor. Thus, these organizing metaphors were used to structure the talk about the displays but not the format of the displays themselves.

The primarily pictorial displays for the cockpit had several pictorial metaphors. One type of pictorial or visual metaphor depicted radar ranges as spheres (called "shells'? or columns (called "search lights'?; in this case, lines that are standardly used to depict surfaces were used metaphorically to depict electromagnetic ranges, which are not solid surfaces (#5). In a different type of pictorial metaphor, flight paths were depicted as corridors, highways (with lines across the "road" and posts beside it), or tunnels (#5). In a third type of metaphor, safe areas were depicted as ponds with shape and depth corre- sponding to safe areas to fly close to the surface in order to use terrain masking. There were no organizing metaphors that united the different elements of the displays and none that made the different pictorial metaphors consistent with each other. Specifically, different kinds of radar ranges, the plane's masking radar, ground weapon radar, and other planes' tracking radar were all portrayed in the same way, except that sometimes the color varied. To be systematic, if these ranges are to be portrayed as surfaces, the different types of radar should correspond to different types of surfaces. The highway was used more systematically in that cross lines, width, and height of path were all portrayed as they are on real highways and corridors. However, no other aspect of the displays was consistent with the underlying metaphor of 'fflying as driving;" that is, driving was not being used as an organizing metaphor. The fact that designers use metaphor intuitively is

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


testimony to its power; however, consciously using metaphor may result in more efficient use, as well as in identifying the limits of any particular metaphor. Perhaps, if designers were consciously and systematically incorporating metaphor into their designs, organizing metaphors would arise to tie together the various elements of the display.

There were two organizing metaphors used in cockpit designs (#6, #7). One was "health, " as an organizing metaphor in thinking about status displays, but it was not used in the actual depictions. As discussed earlier, the health metaphor may have been used to group and order the presentation of displays, for example, those based on hydraulics ("circulation '7, electronics ("nervous system"), and the like, but was not used in depicting the status of the aircraft. The 'pying in formation"metaphor did directly affect the display and did organize one part of the pilot's task (flying at a certain altitude and speed). In addition, this metaphor organized a whole set of decisions for the designer, that is, how to depict critical information on altitude, speed, orien- tation, and the like, because the phantom plane in that depiction showed accelerating, turning, and the like. The "jlying in formation" metaphor did not, however, serve to organize the whole display or the whole mission. This metaphor is appropriate for take-off, ingress, egress, and landing, but not for air-to-air or air-to-ground modes.

The displays that were somewhat iconic, but not to the extent of the primarily pictorial displays, were those described for current, or currently in revision, heads-up displays (HUD). Whereas several aspects of these displays were described metaphorically ("accordion" for the action of a pitch ladder in fast maneuvers (#9), symbols were 'begged" or "caged" if they corre- sponded to variables out of the range of view) the metaphors were not often relevant to the activity of the operator or crew and were not used in the depiction. There is a HUD symbol being used in designs for the LHX helicopter helmet-mounted displays that corresponds to the nose of the helicopter and one designer said it "becomes like the nose on your face," but that metaphor was not expressed pictorially-nothing about the display was face-like. This may be because current HUD displays are primarily indexical and not very iconic, so the opportunities for pictorial metaphors are lessened. Whether HUD displays would work better if they were more iconic and more metaphoric is an open question; two pilotldesigners thought HUD displays would work better if they were more pictorial.

GENERAL DISCUSSION

Verbal metaphors were used in all but one of the designs, either as descriptors or as organizing metaphors. Pictorial metaphors were used primarily in displays for future cockpits and sometimes in missile warning displays. Picto- rial metaphors may occur only in iconic displays, and many older designs are

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


not iconic. Newer designs take advantage of the new hardware and software tools that allow pictorial formats and, consequently, there is more potential for pictorial metaphors. Both pictorial and organizing metaphors were based on activities that are very familiar to both designer and user; that is, locomot- ing on and interacting with surfaces as well as driving or flying in formation. Two metaphors that were based on less well-known activities were the safe- areas-as-water metaphor (diving and moving a vehicle in water is known by fewer people than is driving), and the plane-functioning-as-health metaphor (not well known in detail by either pilots or designers).

Metaphor is used by designers of software, interfaces, and display formats. At present, however, the use of metaphor is ad hoc, with different metaphors for different parts of displays. No organizing metaphors are used systematically to tie many parts of the display together, and designers do not consciously use guidelines or rules for incorporating metaphor into pictorial displays. When metaphor is used systematically, it can be very powerful in organizing the designer's task and in organizing the operator's use of the display; examples are the 'fflying in formation" metaphor that results in a phantom wing leader portrayed for the pilot and the desktop metaphor that organizes commands and icons for word processing. The power of metaphor lies in its potential to organize and provide structure for displays and the use of displays. Domains that are well known to both designer and user can be used to coordinate displays and the actions the displays support. This is why the 'fflying as driving" metaphor and the "wordprocessing as typing" metaphors work so well. This is also why the health metaphor for the status of an aircraft may not work-physiology and diagnosis are not well known and are not often used by designers and pilots. Because two different domains, however, are involved in metaphor, mismatches or areas of dissimilarity will exist, so the potential to hide certain information also exists. The challenge is to understand how metaphors are used in the process of design, how some metaphors are chosen to be depicted, and how much depicted, and how such depicted metaphors are understood by those using the displays.

The phenomenon of visual metaphor also challenges us to identify when and how some metaphors may misdirect attention or confuse the viewer. For example, one designer described developing designs for pilots to check the mechanical functioning of the plane. The designs were based on a "plane as living organism" metaphor and the systems of the plane were described and depicted in terms of the health of the plane. These designs were not useful to the pilots, probably because body functioning was not well known to them in detail and, therefore, could not serve to guide attention and action effi- ciently.

This study confirms that visual metaphors are used in depictions whose purpose is to guide skilled action and decision. Visual metaphor defines a

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


relatively new area of study, and we know very little about how such metaphors are understood and used to guide action. The view that metaphor is a special use of language and entirely a linguistic device (Olson, 1988) would not lead to investigating whether metaphor may appear in existing constructions such as CRT displays. The view that metaphor is a type of rule violation or special purpose classification (Kennedy, 1990) allows for metaphoric pictures, but does not specify how such metaphors may guide perception and action in the real world. The view that metaphor is a process of seeing one thing as if it were a different kind of thing (Dent-Read & Szokolszky, 1993) encompasses metaphor in language as well as in pictures, and accounts for the process of reorganizing perception of an object by seeing it in terms of another (based on resemblance). The fact that visual metaphor is now used by designers in constructing pictorial CRT displays for chemical process control and aircraft attests to the power of metaphor to organize displays and guide attention. Such results also con- firm that visual metaphor is an important type of metaphor that must be included in theoretical accounts of metaphoric thought. Metaphor goes beyond language and aesthetics; it may offer a distinct type of perceiving, understanding, and acting adaptively.

ACKNOWLEDGMENT

This research was supported by contract #F33615-86-C-0544 from the Armstrong Aerospace Research Laboratory, Wright Patterson Air Force Base, Ohio. We acknowledge the creative and thorough work of John Kennedy, Andrew Ortony, Howard Pollio, and Robert Verbrugge, who served as consultants on this project. Mark Johnson and George Lakoff made helpful suggestions and observations. John M. Carroll and his col- leagues provided stimulating discussion and ideas on managing metaphors in interfaces. Mike Nelson, Chris Brezovic, and Roberta Caldenvood provided skilled help in conducting the interviews. We thank all the designers who took time from their busy schedules to talk to us about their ideas.

REFERENCES

Aldrich, V. (1968). Visual metaphor. Journal of Aesthetic Education, 2, 73-86. Aldrich, V. (1971). Form in the visual arts. The British Journal of Aesthetics, 2, 215-226. Black, M. (1962). Models and metaphors. Ithaca, NY: Cornell University Press. Black, M. (1977). More about metaphor. Dialectics, 31, 431-457.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Carroll, J. M. (1983, December). Presentation and form in user interface architecture. Byte, pp. 113-114.

Carroll, J. M., & Mack, R. (1985). Metaphor, computing systems, and active learning. Znterna- tional Journal of Man-Machine Studies, 22, 39-57.

Dent, C. (1987a). Developmental studies of perception and metaphor: The twain shall meet. Metaphor and Symbolic Activity, 2, 53-71.

Dent, C. (1987b). Comprehending concrete metaphors: Developing an understanding of topic- vehicle interaction. In K. Nelson & A. van Kleeck (Eds.), Children's language (Vol. 6, pp. 213-228). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.

Dent, C. (1990). An ecological approach to language development: An alternative functionalism. Developmental Psychobiology, 23, 679-703.

Dent, C., & Rosenberg, L. (1990). Visual and verbal metaphor: Developmental interactions. Child Development, 61, 983-994.

Dent-Read, C., & Szokolszky, A. (1993). Where do metaphors come from? Metaphor and Symbolic Activity, 8, 227-242.

Easterby, R. (1967). Perceptual organization in static displays for madmachine systems. In W. Singleton, R. Easterby, & D. Whtefield (Eds.), Proceedings of the conference on the human operator in complex systems (pp. 95-105). London: Taylor & Frances, Ltd.

Flanagan, J. (1954). The critical incident technique. Psychological Bulletin, 51, 327-358. Fowler, C., & Turvey, M. (1978). Skill acquisition: An event approach with special reference to

searching for the optimum of a function of several variables. In G. Stelmach (Ed.), Znforma- tion processing in motor control and learning (pp. 1-40). New York: Academic.

Gaver, W. (1986). Auditory icons: Using sound in computer interfaces. Human-Computer Interaction, 2, 167-1 77.

Gibson, J. (1979). The ecological approach to visual perception. Boston: Houghton Mifflin. Johnson, M. (1981). Metaphor in the philosophical tradition. In M. Johnson (Ed.), Philosophical

perspectives on metaphor (pp. 3-47). Minneapolis: University of Minnesota Press. Johnson, M. (1987). The body in the mind. Chicago: University of Chicago Press. Kennedy, J. (1982). Metaphor in pictures. Perception, 11, 589-605. Kennedy, J. (1990). Metaphor-Its intellectual basis. Metaphor and Symbolic Activity, 5, 115-

123. Klein, G. (1978). Phenomenological vs. behavioral objectives for training skilled performance.

Journal of Phenomenological Psychology, 9, 139- 156. Klein, G. (1987). Applications of analogical reasoning. Metaphor and Symbolic Activity, 2,

201-218. Klein, G., Calderwood, R., & Clinton-Cirocco, A. (1986, SeptemberIOctober). Rapid decision-

making on theJire ground. Proceedings of the 30th Annual Human Factors Society, Dayton, OH.

Lakoff, G. (1987). Women, $re, and dangerous things. Chicago: University of Chicago Press. Lakoff, G., & Johnson, M. (1980). Metaphors we live by. Chicago: University of Chicago Press. Olson, D. (1988). Or what's a metaphor for? Metaphor and Symbolic Activity, 3, 215-222. Ortony, A. (1975). Why metaphors are necessary and not just nice. Educational Theory, 25,

45-53. Ortony, A. (Ed.). (1979). Metaphor and thought. London: Cambridge University Press. Peirce, C. (Ed.). (1960). Collected papers of Charles Sanders Peirce: Vol. 2. Elements of logic.

Cambridge, MA: Harvard University Press. Verbrugge, R. (1980). Transformation in knowing: A realist view of metaphor. In R. Honeck

& R. Hoffman (Eds.), Cognition andjgurative language (pp. 87-126). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.

Verbrugge, R., & McCarrell, N. (1977). Metaphoric comprehension: Studies in reminding and resembling. Cognitive Psychology, 9, 494-533.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


APPENDIX A

Sample Summarized Interview

I. Interview participants. Designer, Wright Patterson Air Force Base, interviewed by Cathy Dent-Read, Chris Brezovic, and Gary Klein.

11. Biographical data. BS and MS in Psychology, PhD in Industrial Psychology; currently 40% of occupation time is Research and Devel- opment work; has worked on approximately 20 designs for format displays.

111. Incident. A. Problem. The problem is to display on a CRT in the cockpit the important aspects of the pilot's situation; the display is not to be used directly for flying but for knowing deviations from planned path, location of ground weapons, other planes that are trying to track one's plane, and the like. B. Challenge. The challenge is to replace old alphanumeric readouts and dedicated instruments with more flexible pictorial and graphic displays so that pilots have a more immediate awareness of their situation, can make quicker decisions, and better fly the plane and carry out a mission. The challenge is to choose the correct information to display, the right way of displaying it, and the right way of integrating different types of information so that pilots can use the display well. The designer and his contractors are designing for cockpits that will exist sometime in the next 10 or 15 years, so the designs are tested on simulators and hardware is less of a constraining factor as they are not trying to fit into existing planes. C. Solution. The solution was to design three primary flight displays: the heads-up display (HUD), the Vertical Situation Dis- play (VSD), and the Horizontal Situation Display (HSD). We discussed mostly the VSD with a little discussion of the HUD. The VSD shows the view from 6,000 ft behind and 1,000 ft above the aircraft, the aircraft symbol stays stationary and everything moves under it. We discussed several aspects of this display. The circle around the plane the designer called a "shell of protection," it is yellow if no radar is succeeding in tracking the plane, red if an unfriendly source is tracking the plane. The line coming to the shell was called a "tractor beam," which means that a source at the other end of the beam is trying to track the plane. It is "trying to pull in the plane;" the ECM (masking functions on the plane) is "pushing away the tractor beam." If the tractor beam "burns through" then the shell turns red; the designers are now thinking about having a wedge shape turn red at the point where the beam intersects the

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


shell. The areas above ground-based missiles in which the kill probability is 30% to 99% (the probability that the plane would be shot down if it were in that area) is shown as a solid red area surround- ing and extending up from the missile. If that area is yellow, the kill probability is 10% to 30%. Those that are outlined but not filled in are not tracking with radar. The designer called those shapes "searchlights." We talked in detail about the depiction of the flight path for the plane to take. The path is called a ribbon, corridor, highway, road, and the designer even called it a roller coaster to capture the fact that there is a marked vertical dimension. He also often called it a highway and in his descriptions of the design often referred to how "everyone has driven on a highway," in other words it was a frequent experience that was common to both pilots and designers. In all versions of the depictions for the desired flight path there was a path with cross lines so that the path seemed to move under the aircraft symbol. In the corridor version, there are walls extending up from the side of the path and these are marked with vertical lines. The pilot's task is to keep the airplane symbol on the flight path. The walls of the corridor are used for judging altitude above the path, a pathway on the ground does not have to specify an organism's altitude above the path, but that is important for the pilot. When the walls are not there (and sometimes in addition to the walls) a single line extends out either side of the path so that when the aircraft symbol is lined up with those lines the plane is at the right altitude. Dent-Read asked about whether a ceiling is ever depicted as real corridors have ceilings, the designer said ceilings have not been used except for helicopters. In addition to the road with tar strips depiction there are also dashed-line tar strips to show a path back to the desired flight path once the plane has deviated. If the pilot gets so far away from the desired path that the road would be out of view the depiction does not leave the screen but is pegged at the edge where it will reappear if the pilot changes course correctly. Dent-Read asked how the idea of a corridor got started and the designer did not know, pilots may have been the source but that way of referring to the flight path goes back at least to the 1950s. The Navy is now testing a design that has the path indicated by rectangles separated by space (which gives an even better illu- sion of movement) and a fictional plane depicted where a plane would be if the pilot were that plane's wingman.

The fictional plane is used to indicate desired altitude, but also acceleration (the afterburners come on when the pilot should accel- erate), deceleration (air brakes are depicted on the fictional plane), and landing (the landing gear comes down on the fictional plane).

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


As pilots have a lot of experience actually seeing other planes in that formation the phantom plane is a very good and very intuitive way of guiding the plane. D. Alternatives not used. Some revisions were made to the HUD, VSD, and HSD designs after the simulator tests with pilots. When we asked the designer for a design that had not been used he changed to another type of design that was used to show the status of the plane. This becomes another incident. (Two other incidents follow)

APPENDIX B

Descriptions of Selected Display Formats

A. Control Station

1. Problem: Design a user interface for a missile warning officer, who must detect, identify, and file reports on enemy missile launches.

Solution: Create a map display that shows radar ranges that can detect enemy missiles drawn as bounded by solid or broken lines on a map, depict missiles as boxes moving along a fan-shaped surface that corresponds to the probability of where the missile would hit.

2. Problem: Same as above. Solution: Use a second set of displays on a touch sensitive screen,

the user can have a dialogue, scroll text, choose different displays, and give several commands for sending reports or obtaining more infonna- tion.

B. Simulator

3. Problem: Design a workstation for a pilot trainer, who needs to monitor the pilot's flight simulator, monitor the training session, and control the session. Specific problem: Use color to improve clarity and/or performance consistency across many different kinds of training sessions.

Solution: Keep color identification and symbolism constant under a variety of conditions; base color coding on historical, conventional, and attentional factors.

4. Problem: Provide cueing elements that help pilot trainees to attend to important information using the simulator that presents graphics superimposed over video images of real landscapes. Specifically, show the limits of the pilot's weapon so he will know when he can use it effectively.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4


Solution: The cue is a cone (lines and fill) that correspond to where the weapon can reach, or where it will be effective.

C . Flight

5. Problem: Display the current situation to the pilot, using a heads down display.

Solution: Represent a god's eye view, above and behind the position of own plane, plane symbol is in the display. The display is in color; ground terrain, sky, and plane are shown. In addition, there is a highway or projected safe path for the plane, shells of masking radar around own plane, tractor beams of tracking radar from other planes, and search lights (i.e., radar ranges of ground-based weapons, color coded for degree of danger).

6. Problem: Display for the pilot the status of the plane, especially any malfunctions, with directions for remediation.

Solution: Displays show fuel level, avionics, and electrical system, pictorially, with some labels and text. The designer thought of these displays as showing the health of the aircraft.

7. Problem: Provide information that allows pilots to fly on the projected best path.

Solution: Display a "phantom" plane ahead and to the left, (i.e., wingleader position) that portrays correct speed, turns, deceleration, and the like slightly in advance of what the pilot should do; the pilot flies as "wingman."

8. Problem: Design a display for guiding covert, nighttime, terrain-following flight.

Solution: Provide a HUD display superimposed on infrared scene to show with a "side look" the terrain line from left to right, a symbol for where the plane will be in 30 sec, one for where it will be in 60 sec, and a symbol for where the pilot should "push over" or start down after climbing to follow a rise such as a hill.

9. Problem: Display target information on the HUD to facilitate target selection.

Solution: Display four or five targets with iconic symbols at the bottom of the display, filled to the percentage that corresponds to the likelihood of accurate designation, and ordered by priorities.

Dow

nloa

ded

by [

Uni

vers

ity o

f K

iel]

at 0

9:31

25

Oct

ober

201

4

metaphor in visual displays designed to guide action

Documents