Technical Translation: Usability Strategies for Translating Technical Documentation

The Human Input / Output System 
As already stated, humans interact with the outside world and with com-
puters through the exchange of information. This exchange relies on in-
formation being sent and received; in other words the input and output of 
information. 
Information input for humans takes place through the five senses: sight, 
hearing, touch, taste and smell. For most people, the first three senses are 
the most important, especially in terms of human-computer interaction 
(Faulkner 1998:13; Dix 1998:13). Even though the senses of taste and smell 
are valuable senses for humans, it is not clear how they could be utilised in 
our interactions with software or documentation (Dix 
ibid.
) and they will 
not be discussed further here. Similarly, the senses of hearing and touch, al-
though invaluable for humans, are of little relevance in our examination of 
printed user guides; these senses will not be discussed here either. 
Sight – The Visual Channel 
The way in which humans see relies on a highly complex system which 
functions in two stages: the physical reception of visual stimuli and the 
processing of these stimuli (Dix 1998:14). While the physical limitations of 
the eye mean that we cannot see certain things (e.g. ultraviolet or infrared 
radiation etc.) the processing abilities of humans means that we can organise 
visual perception in terms of motion, size, shape, distance, relative position 
and texture (Downton 1991:14), even if some information is missing or in-
complete (Dix 
ibid.
).
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Understanding Users 
The Eye 
The basic principle underlying human sight is the reception of light re-
flected from the physical world. This light represents a stimulus which is 
then interpreted. At the core of this process is the eye which is a firm, 
semi-solid orb consisting of several layers (see Figure 1).
Figure 1: The Structure of the Eye 
The first of these layers is a white outer layer called the sclera which not 
only maintains the eyeball’s shape but provides both protection and a means 
for attaching the muscles that move the eyeball. Inside the sclera is the 
choroid, which is a dark layer containing many blood vessels which nourish 
the various structures of the eye. In addition to this, the dark colour of the 
choroid layer prevents light from being reflected internally within the eye.
The innermost layer of the eye is the retina which contains cells which 
are sensitive to light, i.e. photoreceptors. Towards the front of the eye the 
choroid layer becomes thicker and forms the ciliary body. This part of 
the
eye contains muscles called the ciliary muscles which are used to control the 
shape of the lens which is suspended by suspensory ligaments. Another part 
of the choroid layer is the iris, a coloured circular body which is similar to 
the shutter on a camera. The function of the iris is to regulate the amount 
of light entering the eye. Inside the eye, we can distinguish between two 
different chambers, one in the main body of the eye and the other between 
the cornea and the lens. The first chamber is filled with a clear glutinous 
substance called the vitreous humour. The second chamber contains a less 
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The Human Cognitive System
viscous clear fluid called the aqueous humour. Both humours contribute to 
maintaining the shape of the eyeball. 
The purpose of the eye is to receive light and convert it into electrical 
impulses which are then sent to the brain via the optic nerve. When light 
the cells on the back of the eye (see Figure 2). These cells make up the 
retina.
Figure 2: Refraction of Light Through a Lens 
In a process called accommodation, the shape of the lens is altered by the 
ciliary muscles to focus images from distant objects: when viewing distant 
objects, the muscles relax, making the lens thicker. When viewing close 
objects, the muscles contract to make the lens flat and thin. 
When light enters the eye it has two main properties which are of use to 
the eye: brightness (intensity) and colour (wavelength) (Faulkner 1998:14). 
The light is focused onto the retina which contains two types of photore-
ceptor cells (i.e., cells which are sensitive to light): 
rods
and 
cones
. 
Rods
are very sensitive to light and it is these cells which allow us to see 
in low-light conditions. The average eye has around 130 million rods 
(
ibid.
), most of which are located towards the edges of the retina (Dix 
1998:14). Rods, however, are not very good at detecting detail and are 
subject to saturation. Saturation essentially means that the cells become 
“overloaded” by light and this phenomenon explains the temporary blind-
ness experienced when moving from dark into light (
ibid.
). Rods are also 
unable to detect colour. 
103 
enters the eye, it is refracted by the lens and focused to form an image 
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Understanding Users 
The second type of photoreceptor is the 
cone
. There are three types of 
cone, each being sensitive to a different wavelength of light. In the average 
eye there are approximately 6-7 million cones and they are mostly concen-
trated on the fovea which is the target on the retina where images are fo-
cused. Cones are less sensitive to light and they can detect colour. This 
means that we can detect colour if the object is in our main field of vision 
as opposed to our peripheral vision. There is a point on the retina which 
does not have any photoreceptors and which cannot detect light. This is 
called the 
blind spot
and it is where the optic nerve connects to the eye. 
In addition to photoreceptors, the retina also contains special nerve cells 
called
ganglion cells
of which there are two types: 
X-cells
and 
Y-cells
. 
X-cells are concentrated in the fovea and are responsible for quickly detecting 
patterns. Y-cells are distributed across the retina and are responsible for de-
tecting movement. But how is it that these physical structures transform the 
physical stimulus of light into useful information which we can understand?