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Human – ComputerInteraction
Assignment 1
Jahmel Matthews
UNIVERSITY COLLEGE BIRMINGHAM
,Jahmel Matthews
1|Page
Human-Computer Interaction
Human-Computer Interaction
HCI (Human-Computer Interaction) is the study of the interaction between people and computers
fundamental principles. The first principle is perception, this is the process in which organism
interpret and organise sensation in to produce a meaningful experience of the world; this is
fundamental in HCI as if we are unable to see a display or hear a warning then we are unable to
respond correctly. The next principle is Schneiderman’s eight rules these are:
Strive for consistency – consistent sequences of actions should be required in similar situations,
identical terminology should be used in menus and help screens, an example of this would be if in
the settings a home screen is referred to a home screen and then in the help menu it is referred to
as the desktop, this is bad as it means that users are unsure as to what to do as they haven’t any
definitive answers from the lack of consistency. This also applies to colour schemes, fonts and
layout. Without keeping these consistent, the interface looks unprofessional.
Enable frequent users to use shortcuts – experience users often have the desire to feel as if they’re
dominant over the interface and its actions, this means that they would rather not have any
surprises or changes that may counter their knowledge, they would find this tedious. To avoid this,
shortcuts are put in place so that experienced users have easier access and get the satisfaction of
feeling as if they’re above the interface.
Offer informative feedback – for each user interaction, interface feedback should be implemented,
for frequent and minor actions the response can be modest, such as clicking on the bold button in
Word, highlights it. But for infrequent actions the response should be more visible, such as pressing
enter on a form brings up a validation box for the user to affirm that they made the right decision.
These are put in place as visual representations provide relief to the user as they know their request
has been acknowledged.
Design dialog to yield closure – sequenced actions should be organised into groups with a
beginning, middle and end. Feedback at the completion of a sequence offers users a sense of
accomplishment as they’ve finished their task. This allows them to drop contingency plans from their
minds and reduces stress; it also offers a signal to prepare the next sequence of actions. An example
of this is how when using a self-checkout, it moves from scanning products to the checkout with a
clear confirmation page that completes the sale.
Offer simple error handling – interfaces should be designed so it’s as hard as possible for users to
make serious errors while using it, an example of this is making areas that can’t be accessed grey or
not allowing typing in a drop-down list, this heavily relies on validation. In the off case that users do
make an error, the interface should offer simple, specific instructions to recover from their error. An
example is that users should not have to fill in a whole form again if they forgot to fill in one box;
rather be guided to the part where the error is located. As a result, erroneous actions should leave
the interface unchanged.
Permit easy reversal of actions – actions should be as easily reversible as possible, this alleviates
anxiety from the user as they know they have a contingency for if something goes wrong, this
encourages exploration of unfamiliar features. Reversibility could be anything from reformatting a
document to adding a single deleted letter.
, Jahmel Matthews
2|Page
Human-Computer Interaction
Support internal locus of control – when designing an interface its imperative that the user has
control and freedom so they feel that they can be free and control the system themselves, this is
due to the fact that free will assures the user.
Reduce short-term memory load – Humans have a limited memory capacity for processing
information in short-term memory with people usually being able to remember 7 (give or take two)
pieces of information at a time, this leads to designers avoiding interfaces that require users to
remember information from one display and use it on another. An example of this is phones not
requiring a re-entry of numbers as they can be saved. To keep interfaces simple, website locations
should be visible at all times and lengthy forms should be compacted to fit on a small display.
The final principle is behaviour models, there are two types of behaviour model in HCI, these are
Predictive and Descriptive.
Predictive modelling is a mathematical process used to predict future events by analysing patterns in
each set of input data; examples of predictive behaviour models are the Keystroke Level Model, Fitt’s
Law and the Key Action Model.
The Keystroke Level Model was constructed in 1980 by an American researcher called Stuart. K.
Card, an engineer called Thomas P. Moran and a researcher by the name of Allen Newell; it is a
relatively simple tool that allows a designer or researcher to gain an approximation of how long
experienced users will take to complete a routine task in their software The model consists of 6
operators: keystroke, pointing to a target on the display with a mouse, homing hands on the
keyboard, manual drawing, mental preparation for physical actions, and response time. Keystroke
(the most used operator) executes a single character press (e.g., pressing the “J” key), the time it
takes to perform this operator is dependent on the user’s motor skill and experience, this can be
tested by doing one-minute typing tests. After the tests, you take the total test time and divide it by
the number of successful keystrokes with no errors. This allows the user to determine typing speed.
Pointing to a target on the display with a mouse depends on the sensitivity of the mouse as well as
the distance between the cursor and a target and the size of the cursor. Ergonomics of the device
correlate with the homing hands on the keyboard but doing this increases the speed of the users
pressing a key. The manual drawing operator is limited to the mouse and does not include any other
input device. This means that the user can only draw straight-line segments using the mouse. The
length of the lines drawn is represented by nD straight-line segments with a total length of D (nD, lD)
cm, where nD represents the number of straight-line segments and lD represents the total length of
the segments in centimeters. This operator in the Keystroke Level Model enables the user to
manually create straight lines using the mouse. Mental preparation heavily depends on the user as
the more knowledgeable and skilled the user is the quicker, they will execute the action. The
response time of a system is directly proportional to the motor skill of the device, this means the
quicker the device the quicker the response time. Although this model is highly detailed there are
still limitations, these include that it measures only one aspect of performance meaning that it will
not measure time taken to learn a task, it is only designed for experienced users with knowledge and
motor skill, it only considers routine unit tasks, and that the execution of the method must be error
free, or it won’t work.
The Fitts’ Law is significant as it helps designers and
engineers understand the basic principles of human
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