Topic 6  Human-Computer Interaction

Computers are designed to be used by people to improve productivity at work.  The human-computer interface is an important area of work, because not every computer user is an expert.  Working with computers has been made very much easier in recent years by people who have thought the interface out very carefully:

• Common file menu structures;
• Common short cuts, for example CTRL+S means save;
• Colourful layouts and meaningful icons;
• Logical layouts.
• Cheerful little animated characters that provide a natural language help (I use Rocky, a happy little doggy character, but there are many others);
• Various noises.  One of the most appropriate is the explosion noise for a program error. 

Some people sneer at these, but many others, myself included, like them.

Other than the interface, there are other need that computer users have that are covered by the discipline of ergonomics.  Ergonomic measures ensure that workplaces are safe and productive places:

• Simple measures such as a tidy desk and office (not one of my strong points!), with wires kept out of the way;
• Lighting - the office should not be underlit or overlit.  Computers should not face a sunlit window (mine does).  There should be blinds to reduce the glare from the sun.
• Furniture should be adjustable and comfortable.  People who work with computers must have swivel chairs.  The computer equipment itself must be adjustable.  Repetitive Strain Injury can be a problem, and employers must take reasonable steps to reduce it.
• Energy efficiency is important.  It is said that computers can take up to 10 % of an organisation's total energy bill.  Many computers get left on overnight and over the weekend; not very economical.  Computers can be set to go into "sleep-mode" if left un-used.

Question 1.  What resources and factors should an employer consider in designing an office in which computers are going to play a key role in the work?  ANSWER

Psychological Factors

What I know about psychology could be written on one side of A4!  However many psychologists have worked with developers of computer software.  Their findings have been important in helping developers produce systems that are designed well and get a reputation for being user-friendly.  People get information into their noddles by:

• Vision - the eye is less sensitive to blue light than red or green (whoops; these notes are in dark blue text on a light blue background - I didn't know that when I adopted my house-style).  Important information should not be presented as blue text.  Also no interface should be entirely dependent on being able to distinguish colours, since red-green colour blindness affects 8 % of men.
• Hearing - sound is important.  Humans react quicker to auditory warnings than to visual.  Some functions are associated with different sounds.  Emptying the Recycle Bin is associated with a sound of paper being scrumpled up or shredded.  I always associate a program error with an explosion sound.
• Touch - you don't need to have to push down on a key, but there is some kind of psychological need to do so; it feels more positive.  A touch-key pad in which a character only needs to be touched, not pressed down would not be liked as much as an ordinary keyboard.
• Movement - icons need to be relatively large  so that users with poor motor control can still manipulate them.

We have two kinds of memory:

Short-term memory - a bit like the RAM on a computer.  Most things we learn are initially stored in short term memory.  Something like a telephone number is committed to short term memory.  Short term memory is aided by grouping characters.  It is easier to remember 0131-667 3042 than 01316673042.  Other patterns such as words also help in short term memory.

Long term memory - a bit like a hard-drive.  It is different to short-term memory.  It is almost limitless.  It also has a slow access time, about 0.1 seconds.  Forgetting is slower in long term memory.  Information is passed from short term to long term memory by repetition.  Also if there is a definite pattern, the material gets committed much more quickly, especially if it fits in with other ideas.  For example:

        Ohms law acceleration divided seconds by metres on circuit not heat.

This is meaningless, so would be hard to commit to long term memory.  Don't waste your time trying it either.  However this statement makes more sense (to a physicist):

Ohm's law states that the voltage across the ends of a conductor is proportional to the current, provided the temperature is constant.

We also have pictures that we have built up through experience.  Consider this sentence:

We took the dog to the surgery.  After seeing the vet we took him home.

We know that this means that the dog had something wrong.  We explained the problem to the vet, who examined the dog, diagnosed the condition, treated the dog, and then we went home with the dog.  It could mean that we went to the surgery, took one look at the vet and took the dog home.  Or we took the vet home.  But we know that the first meaning is most likely to be true.

Computer users learn competence at their software by practice.  Gradually it sinks in.  Five years ago I knew next to nothing about computers (who said still doesn't?  Confess!).  Now I would describe myself as a competent computer user.  There are still things I have not yet learned, but will learn by practice.   Good interfaces will provide imagery that will coincide with our experience.  For example a red cross means STOP, NO.  A green tick means OK, GO.  A folder looks like a cardboard folder you find in a filing cabinet.  A task list looks like a clipboard with a list.

Some abstract concepts like file properties have no icon associated with them.

Good Software Design

Computers are daunting things for many people.  Repeated failure at mastering software rapidly makes people feel diminished and they will rapidly give up.  Developers need to find out what is good about software, and the areas in which people have more trouble.  Even an expert can find bad software infuriating.

The Human Computer Interface (HCI) is developed in very much the same way as the systems life cycle which we saw in Module 4.

The best HCIs will provide:

• Easily understandable help for novices without the use of computer jargon;

• Short cuts for experts;

• Icons that are easily interpretable, for example, a printer for the print function;

• Consistent actions, like F1 for help, and CTRL+Z for undo.

• Escape to get out of trouble, or undo last action.

• Helpful error messages.

• Uncluttered screens with effective user of colour with easily read text.

Graphical User Interfaces (GUI) are much more user-friendly but have some disadvantages compared to the command-line interface:

• Take up more memory;

• Need more disk space;

• Run more slowly;

• More time consuming to an experienced operator than typing a simple command line.

In modern computers systems, these drawbacks are much less of an issue and the advantages to the average user far outweigh the drawbacks.

Question 2  Give four physical and psychological factors that govern how people interact with computer systems.  (NEAB Past Question, Part (a))  ANSWER

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