Chapter 1

The Human

1.1 Devise experiments to test the properties of (i) short-term memory (ii) long term memory, using the experiments described in this chapter to help you. Try out your experiments on your friends. Are your results consistent with the properties described in this chapter?


The aim of this exercise is to get the student to think about experimental design. The experiments devised can effectively be repeats of the originals. Chapter 11 can be used for reference on experimental design.

(i) Short term memory (STM)

The student should first choose an aspect to investigate: for example, digit span, recency effect, decay.

Example solution: STM decay
ideally selected to represent population, more probably undergraduate students (try to get a range of academic subjects).
Sample size: 10+

split subjects into two groups. Each subject studies list of 15-20 words (could try with both nonsense words and actual words to see any difference). Subject has to recall list either (a) immediately or (b) after 20 second delay. Measure the number (or percentage) of the words remembered correctly.

A within-groups design can be used to avoid individual bias or group variation (as long as different lists are used for each attempt).

independent variable -- delay in recall
dependent variable -- number correctly recalled.
Group (b) should be given a task to do during the delay period in order to avoid rehearsal. If possible this task should occupy a different channel to minimise interference, e.g. a visual recognition task.

Those in (b) will perform worse than those in (a) since STM will decay.

graphs to see decay.
T test

(ii) Long term memory (LTM)

The student should first choose an aspect to investigate: for example, the total time hypothesis or the distribution of practice effect.
Example solution: distribution of practice effect
as above. Should have no prior experience of the skill to be learned.

split subjects into 3 groups. Each subject must learn a skill (for example shorthand or typing -- must be measurable). Group A learns for 1 hour a week for 6 weeks. Group B learns for 2 hours a week for 3 weeks. Group C learns for 3 hours a week for 2 weeks.

After each group's training is complete the subjects are tested and the number of mistakes made are noted.

Between-groups design.

independent variable -- style of learning
dependent variable -- accuracy
Group A will be best (due to the distribution of practice effect)


(N.B. This one is not easy to run but could be done with cooperation from friends)

1.2 Observe skilled and novice operators in a familiar domain: for example, touch and 'hunt-and-peck' typists, expert and novice game players, or expert and novice users of a computer application. What differences can you discern between their behaviours?


1.3 From what you have learned about cognitive psychology, devise appropriate guidelines for use by interface designers. You may find it helpful to group these under key headings: for example, visual perception, memory, problem solving, etc, although some may overlap such groupings.


Guidelines are just what they say they are: guidelines. They provide for a consistent look and feel for an interface, as well as trying to exclude the more obvious mistakes that can be made from a psychological perspective. However, there are occasions when such constraints should be broken; for new interaction devices, for example, or to create a unique style of product.

Because of this, there is no one correct answer to this question: some will be more cognitively friendly than others, that is all. Guidelines can range from the general principle type shown below down to highly detailed information on what each component in a display should look and behave like.

Some examples of guidelines with cognitively solid foundations are shown below - this is not an exhaustive set by any means.

This exercise should encourage students to look into the literature on human factors, cognitive psychology and human physiology, and come up with some hard evidence about human limitations. This can then be used to provide informed guidelines. The results of a similar exercise can be seen in some Example Guidelines produced by students.

Worked exercises

The following appear as worked exercises in Chapter 1:

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