Title Page
List of Figures
List of Abbreviations
What is usability anyway?
Importance of improving usability
User centred design
Case Study

Appendix 1

Appendix 2



Feedback Systems

Introduction Next Section

Feedback can be seen as a "fundamental principle" [Cox & Walker 1993] in interactive systems. Without it a user will have no idea what state the system is in and whether his input has been actioned. According to Norman [1988] feedback is defined as the "sending back to the user information about what action has actually been done [and] what result has been accomplished". The user in turn can then decide that the task is complete or that further action is required.

I will, in this chapter, go into more depth about how feedback is considered and demonstrate why it is important to the overall design of interactive systems.

Future, Present and Past Feedback

Barfield [1993] widens the concept of "past feedback", as described by Norman, by adding two more. Firstly "present feedback" which involves informing a user of what is actually happening currently. For example the Windows mouse pointer depicting an hour glass timer which indicates that the computer is in a state of processing. Secondly "future feedback", which she concedes could be "called ..Feedforward", which may enable a user to ascertain what would happen if a certain choice was made. For example a Windows confirmation dialogue box allowing a second chance to avoid deleting a file.

I would suggest, therefore, that there is an obvious link between feedforward and guessability. The more aware the user is made of the results of available choices, the greater the chance of him choosing the intended course of action. In effect the system becomes more guessable to the user. Guessability is further discussed in chapter 5.

Barfield [1993] also isolates "..three channels [of feedback]: sight (visual feedback), hearing (audio feedback) and touch (tactile feedback)". The design of certain systems do not necessarily rely on the one form of feedback but may involve a "combined feedback" [Barfield 1993]. There is a good example of this in The Valve Wheel.

Ensuring Continuity

As well as knowing what has happened to a system, it would seem wise to give a user some form of feedback to 'link' each of the before and after states. In Barfield et al [1993], she gives an example illustration of "iconising a window ...[where]... the user sees the window suddenly disappear and somewhere on the screen the corresponding icon appears". Continuity in the form of a reducing animated wire frame around the window down to the boundary of the icon may be used to enhance feedback, giving the user notice of where his window has gone to [Apple Computer Inc. 1986]. Barfield et al [1993], describes the way "our visual perception... makes us more aware of animated than static visual features"; she suggests that it "makes sense to exploit this sensitivity to animation when designing". There is, therefore, little excuse, with today's powerful systems, not to include the simplest of animations in their interfaces.

Feedback Systems Previous SectionNext Section

The Sign and the Use of Colour

Not all interactive systems need to be complicated. A sign is an example of an interactive system that needs no input by the user, viewer in this case, to obtain output. Although not an interactive system in the true sense of the word, the humble sign can give feedback simply, quickly and can pass on the message with ease. In the same manner it can also give an ambiguous and possibly conflicting instruction or piece of advice if it has been poorly designed. However what constitutes good sign design?

The design of a usable system is dependant on various criteria. As Preece et al [1993] state: "Designing usable systems requires knowledge about: who will use the system [and] what it will be used for...". Using these items as the test criteria for a good sign design consider the examples at figures A and B. It can be assumed that both signs are for use by the general public (the users) and are to convey an instruction and some advice respectively (the tasks). This assumption can be clarified as follows:

The advantage of using graphical representation on the signs rather than words, is that the message given can be received by a wider audience. For instance a sign stating 'No Smoking' will not be understood by those who cannot read or people who cannot read English. Therefore, at an international airport for example, use of the sign shown at figure A (a cigarette with a line though it) will give a clearer message to more people thus increasing usability and the effectiveness of the sign.

The use of colour in signs will also have an effect. The assumption that figure A is a sign giving an instruction and that the sign shown at figure B is an advice sign can be confirmed by their colour. The red/green, stop/go scenario can be seen throughout society (Traffic lights are an obvious example). Designers not only use this aspect to aid their designs but are indeed expected to use it to reinforce users' preconceived ideas.

Figure A
Figure B

Crisp packets are another example where a specific colour is expected for a specific flavour. Similarly, mint sweets are usually packaged in green or blue and never in red. Expectation can therefore determine the colour of something which in turn can, in itself, be used as an aid to identify its meaning or purpose. Mayhew [1992] confirms that "colour associations can be exploited in computer user interfaces".

Preece et al [1993] continue with the next point to take into account when designing a usable system: "...the work context and environment in which it will be used...". Using this item as the test criteria for a good sign design consider the examples at figures C and D

These signs, take into account the nature of the environment in which they are to be used, i.e. a burning building because both signs are fluorescent which therefore increases the chances of being viewed in a smoke filled room. However only figure D conforms to the EEC council directive for emergency escape designs 92/58/EEC 24/6/92 [Colin Davis 1993] again demonstrating the importance of the universal nature of the graphical interface.

Figure C
Figure D

This section has only outlined some guidelines as to what makes an effective sign design based on who the user is and the way he expects to be informed. However the lessons learned in the design of simple signs can be easily transferred to larger projects.

The Valve Wheel

Another interesting interactive system that can demonstrate effective feedback, and yet is based on the simplest of design ideas, was discovered on my recent visit to U-boat 534. The submarine is based in a museum in Birkenhead, on the Mersey river, and is open to the public. The scenario involves the design of the 4 wheels which control the ballast valves, whose task is to raise or lower the submarine.

The valve wheels have been specifically tailored to take into account a total blackout during a voyage, perhaps as a result of loss of battery power. If the submarine had suffered a depth charge attack, which had possibly caused the blackout in the first instance, any error in the use of the valves may result in fatalities since the submarine may unintentionally manoeuvre to the incorrect depth and be damaged. Therefore the valve operator must be able to instantly know which valve to turn in complete darkness.

There are 3 ingenious design features that offer feedback to the operator to help in this task during a blackout:

  • There are two wheels that raise the submarine and two to lower it. One set of wheels has been reversed onto the screw valves, not by mistake as noticed by a casual observer but intentionally, so that the operator will know which set is which, by the sense of touch. See Figure E
  • The number of spokes on each valve wheel varies too, again to give an indication of which wheel is being felt.
  • The final, simplest and most effective indicator uses the sense of sound. Each wheel has been cast using a different amount of metal and when struck with a metal implement, such as a spanner, will ring with a differing tone to the other three.

This example demonstrates three channels of feedback in the one system.

Figure E

The Video Recorder

Even if Bill Gates's original vision of the PC being "on every desk and in every home" is not now a realistic one [Gates 1996] there is no doubt that the majority of homes in the western world over the last 20-30 years have still been invaded by IT. Despite the blandness of the record/watch later concept, the VCR contains a significant amount of computing technology.

Considering that VCRs, and other items of domestic technology, are used by the whole range of the population, there has been much criticism on the poor levels of usability of these items. As considered by Nuttall [1995] "Complicated gadgets bristling with buttons are making our lives more difficult when they should be getting easier".

Even just concentrating upon the humble VCR there is a litany of complaints. One example is the reset or time out mode which resets the machine if the owner pauses while programming it. As Thimbleby cited in Nuttall [1995] details

"If you have to stop to look at the instruction manual, which you nearly always have to do, the thing wipes out what you've already done. It's infuriating, and quite unnecessary".

He continues with another example of poor feedback concerning the on/off light of some VCRs which stays on for a moment after the recorder is switched off:

"If I worry that maybe I haven't really switched the thing off and I press the button again, the recorder enters 'child lock mode' which really messes things up. Such problems are all entirely typical, all entirely avoidable" [Thimbleby in Nuttall 1995].

Interestingly, I have a similar problem on the Compaq PC at my office; I have tended to switch the monitor off but the green light indicator, on the switch itself, takes a few moments to 'cool' off. I therefore tend to re-switch it on again before I realise I have indeed switched it off in the first place. I am aware of it now but when the PC was new I would often leave the monitor powered on all night without realising.

There have been efforts to try and avoid the acknowledged problems of usability in video design. One design, Video Plus, which is licensed by Gemstar Development Corporation and used as a standard by most video manufacturers including the Sony Corporation [1993], attempts to simplify one of the biggest areas of upset, programming. Instead of the video operator having to input start and finish times, date and channel of the required program, a numeric code (PlusCode) of up to 8 digits is used. These codes are displayed next to their relevant programs as listed in newspapers and other publications and can be typed into a remote commander (hand-set) ready for transmission to the VCR itself.

The system works well, is simple to operate and also has a preview facility, on the remote commander, to check the program details before final transmission to the VCR, although there is a necessity to purchase the codes (e.g. a paper) for the system to function.

Reducing Stressful Feedback

Not all feedback is welcome. I suggest that the feedback giving advanced warning, as described by Barfield in Future, Present and Past Feedback as feedforward, could be prone to adding stress to an experienced user of a system. I return you back to the Windows file manager delete confirmation dialogue box, noted in Future, Present and Past Feedback, which gives a good example of an interaction event which could cause annoyance to a user (interaction is discussed in Interaction). Experienced users of the windows file manager would become quite frustrated if every command was re-questioned. One way in which annoying feedback can be reduced is to put the user in control of the system he is operating.

The Microsoft Corporation assumes that stressful feedback will exist, for some users, in their Windows system (the user base is massive after all) and have designed it to be user controlled via customisation. As the Microsoft Corporation [1993a] point out

"If you do not want a confirmation message to appear each time you delete or replace files and directories, you can change the confirmation settings".

Software applications such as Quicken, a home accounts package, include future feedback in the form of prompt boxes/cards. These Qcards, as they are known, pop up automatically on screen to "help you enter the correct information" [Quicken 1994]. The advantage of this system is that the user has an option to turn off just those cards he wants to, thereby aiding where it is needed and not where it isn't. Eventually, as the user becomes progressively familiar with the package, the need to activate these cards will lessen. Their prime aim is to train the user, of course, but they have the ability to do this without placing stress on developing or experienced users.

Conclusion Previous Section

Feedback can be compared to light in photography. Without light a photograph will be blank; however when light is added other factors become apparent to play their part in the whole creation of the photograph. Similarly feedback not only throws light onto the state of a system but highlights, and in turn is affected by, other factors which affect overall usability such as the user's interpretation and perception of it.

I have, in this chapter, demonstrated why feedback is fundamental in the development and design of interactive systems. Feedback can be considered to be the communication between the system and the user without which he will have no way of knowing what has occurred, what is occurring and what will occur if a certain action is taken.