Download Introduction to HCI: Human I/O

Introduction to HCI: Human I/O
Sandra Alshabben
s9sskuhn@stud.uni-saarland.de
Proseminar Mensch-Computer-Interaktion
Department of Computer Science, Saarland University
Abstract. In this paper we will discuss the central character in humancomputer interaction, the human. We will see how human receive information, how he stores the information and how he can make use of the
information he got in order to solve problems. In addition we will see how
our discoveries can help us to create user-friendly interactive systems.
1
Introduction
Human-computer Interaction (HCI) is concerned with design, evaluation and
implementation of interactive computing systems for human use and with the
study of major phenomena surrounding them. It deals with the interaction between users and computers. The basic goal of HCI is to improve this interaction
by making computers more usable and receptive to the user’s needs. That means
that we want to make the barrier between the human’s cognitive model of what
they want to accomplish and the computer’s understanding of the user’s task as
minimal as possible.
The central character for interactive systems is the human. In order to design a system which fullfils the requirements of the user we need to understand
capabilities and limitations of the human body , human’s thinking as well as
human’s psychology.
In this paper I will discuss the role of human beings for designing interactive
systems.
2
Outline
Chapter 1 is the introduction to this paper , followed by a short outline. In chapter 3 we will have a closer look at human input and output channels. That means
we will discuss how human receive and send information. Chapter 4 talks about
human memory. Here I will explain human information storagy, remembering
and forgetting. After that chapter 5 information processing will give a deeper
insight in how human can remember, forget and retrieve information. The last
chapter 6 is about human thinking and will contain the aspects reasoning and
problem solving. Finally this paper will end with a little conclusion.
3
Input-Output Channels
A person interacts with a computer through sending and receiving information.
The user receives information as input which is output of the computer and
can response by sending information as input to the computer. That means the
human’s input is the computer’s output and vice versa. Human can receive information mainly through the senses. We call these senses human input channels.
There are five different input channels, vision, hearing, touch, taste and smell.
The first three channels are the most important for HCI purposes. Human output on the other side occurs through motor control of human body parts like the
limbs, fingers, eyes, head and the vocal system. Of course the fingers play the
most important role for interacting with a computer. We need them for typing
at the keyboard and controlling the mouse. When you use an application at a
computer, you interact through an interface with menu bars, icons and windows.
By interacting with the interface we receive information mainly through sight.
To understand human sight we will have a closer look at the visual input channel
now.
3.1
Visual Input Channel
We can divide the discussion of vision into two aspects of interest, first the physical perception of the human eye and second how we process and interpretatiob
the information we see.
Physical Perception of the Human Eye It is important to have a complex
knowledge of the anatomy of the human eye to understand what can and can
not be perceived by a human being. This knowledge can be a helpful tool to
design user-friendly computer systems.
In Figure 1 we can see the most important components of the human eye.
At the front of the human eye are the corea and the lens. The light is
reflected from objects and received by the corea of the eye. The light is then
transformed into electrical signals which are sent to the brain. The corea and
the lens focus the light into a sharp image at the back of the eye. The place where
the image is projected is called retina. The retina is light sensitive and contains
two types of photoreceptors, the rods and the cones. The human eye has about
120 million rods which are highly intensive to light and allow us to see under
low level of illumination. They are unable to resolve fine details and are subject
to light saturation. That means for example when we move from a dark place
to a highly lighted place we will have the intention of a short blindness. This is
caused by the rods which are saturated by the sudden light intense. In contrary
the cones are less sensitive to light and tolerate a higher level of illumination.
There are three different types of cones. Each of them is sensitive to a special
wavelength of light. They are responsible for our colour vision. The human eye
contains about 6 million of cones which are concentrated at the back of the eye
Fig. 1. Anatomy of the human eye
where the f ovea is situated. The fovea is the point at which the received image
of an object is fixated. The cones are packed more densely towards the center of
our visual field. So when we design a user interface it is important to consider
the fact that a user who is concentrated at the middle of the screen will actually
not pay attention to a help text at the bottom line. This problem could be solved
by using moving icons or flashing error messages which will definitely catch the
user’s attention. The retina also contains nerve cells called Ganglion cells. There
are two types of Ganglion cells , X-cells and Y-cells. X-Cells can be found at the
fovea. There task is to enable us to recognize patterns in images. Y-Cells are
located at the retina. They help us to perceive movement early.
Processing and Interpretation of Visual Information In order to design
effective visual interfaces, we need to know how human perceive size, depth,
brightness and colour. For this it is important to see how an image appears on
the retina. Reflected light from an object forms an upside down image on the
retina. The size of this image is specified as the visual angle.
In figure 2 shows how we can calculate the visual angle. If we draw a line
from the middle of the eye to the top of the object and a line from the center to
the bottom of the line then the angle between those lines is the visual angle.
Two objects of the same size which have different distances have different
visual angles. But two objects with different size and different distances may
have the same visual angle. When we know the visual angle of an object and
it is going away from us, we should perceive it as smaller. But this is actually
not the fact because even if the visual angle of an object changes its size will
remain constant. This is called the law of constancy. Through this law we can
see that perception of size doesn’t depend on the visual angle. There are other
Fig. 2. Visual angle
factors that play a role for perceiving size. One of them is depth. There are a
number of cues which help us to determine the relative position and distance
of an object. For example the overlapping of objects will lead us to think that
the covered layer is in the background and the other is nearer to us or even
the expectation a human has about an object. When we see a mountain and
houses in its near area, we can perceive that the houses are much smaller than
the mountain. So our familarity with an object’s size is also a hint to perceive
is real size. These facts can also be used when we want to design advertisments.
We can put a humorful niance into our advertisment when we for example let
a man walk away from a bottle in the foreground and then he bumps into the
same bottle which is suddenly giant in the background.
Another aspect is brightness. Brightness is a subjective reaction to levels of
light. It is affected by luminance. Luminance is the amount of light emitted by
an object. Our visual system can compensate changes in brightness. In dim light
the rods predominate vision, in low light we can see objects less easily because
the fovea is responsible for our vision and there are just a few rods in its area.
Visual acuity increases wih increased illuminance. So when we want to design a
user-friendly computer, it may be better to use computers with a high display
luminance, so that reading will be easier for the user. A high luminance also
increases flicker, so when we have a larger display it also means that we have
more flicker. That is why we have to reflect about these circumstances when we
design a computer for our users.
As we have seen before the cones are concentrated at the fovea , so this is
the place where colour vision is best located. Just 3-4 percent of the fovea is
covered by blue sensitive cones. As a consequence we should take care not to set
blue as the dominating colour when we design computer interfaces because the
user will find it uncomfortable for reading. And another point is that we need to
consider human that are colour blind. We need to adapt our interactive systems
to provide also solutions for disabled people.
Reading When we read a text, our eyes perceive visual signals. First we can
recognize words as patterns on the page that we read. Then the words will be
transformed into a language specific representation. After that this representation will be analyzed semantically and syntactically. While reading a sentence
our eyes move quickly around. We call these movements saccades. Moving our
eyes from the beginning of a sentence to the end of the sentence is called regression. Between those moving stages our eyes rest from time to time. In this
time we perceive the read text. There were experiments which should show what
makes reading easier for human beings. If we already know a word, it is easy for
us to read it because we match its pattern with our already known word shapes.
The font also plays a role here. For example it will be easier to read words which
use capital letters too and not only small letters. It is also shown that a font size
between 9 and 12 is read without difference. This means that we need to adapt
such experiences to our interface designs. Reading from books seems to be more
comfortable than from computer screens because book pages are more familiar
to read or even the font seems to be more familiar. That means we should reflect
how we could create better readability for our users.
3.2
Auditoral Input Channel
Hearing is another important input channel. The human ear receive vibrations
called sound waves from the air and transmits them through various stages to the
auditory nerve from where the impulses are sent to the brain. Each ear receives
different sounds which are then coupled together so that we can judge from which
location the sound comes. Our auditoral system conveys information about our
environment in this way. For example when we close our eyes and listen to the
noises around us, we could hear cars driving which are on the street behind us.
The auditoral system filters sounds so that it allows us to ignore background
noise and concentrate on important information. For example when we are in a
crowdy noisy place we could also recognize our name when it is spoken. We can
make use of the functionality of our auditoral system by using special warning
sounds to catch the user’s attention while he is interacting with a computer.
Or we could use special sounds for computer games which will give the user a
feeling of reality. And especially for people who suffer from blindness hearing
plays a very important role for interacting with computer systems. Blind people
rely on acustical aids when they use computers. For example the opportunity
that a website is read for them or that the location of a bottom is said to them.
3.3
Haptic Input Channel: Touch
Touch occurs through the skin. The skin contains three types of sensory receptors. Each of them responds to a special feeling. One for heat and cold , another
for intense pressure , heat and pain and the last one for pressure in general. The
receptor for pressure is the most concerned with HCI. It can be divided into two
types, one for immediate pressure as the skin is indented, that means that we
react faster with increased pressure, and one for continuously applied pressure.
When we press a button while using a computer, the feeling of the pressed button
gives us a feedback. Otherwise we could not directly know that we pressed the
button at all. Touch gives us also an awareness of the position of our fingers on
the keyboard. Such an awareness is called kinetesis. Thus when we design computer systems the haptic factor plays an important role for users whose other
senses are impaired. In this case for example keyboards which support braille
may be the primary information resource for them.
3.4
Human Output Channel
Human output is characterized by motor control of aquipment we use and movement of our body parts. In this subsection we will discuss how our movement
affects our interaction with computers. An action like hitting a button is a response to a question which we received through sensory receptors. We do an
action in a special amount of time. This time can be divided into two time
phases. At first the reaction time. In the reaction time we get a stimulus from a
sensory receptor such as vision, hearing or touch and this stimulus is transmitted to our brain. In our brain the question is processed and a valid response is
generated. Then the brain sends an signal to the muscles. The time we need for
that depends on the sense of the stimulus. An auditory signal needs 150 ms, a
visual signal needs 200 ms and for example pain needs even 700 ms. Through
the signal of the muscles, body parts start to move. The time to move one part
of your body is called movement time. For example when I move my hand to
click a button on the keyboard. This time depends on physical aspects such as
age and fitness.
The amount of time which is spent by the user to solve a task depends on the
abilities of the user and the task itself. For example a user who plays a specific
game very often, will be faster in reacting as a user who plays the game the
first time and will make more mistakes. When the user needs more time to solve
a task, this will reduce the correctness of the task. This effect should also be
considered when we design interactive systems. We need to make the distance
to a particular button or icon on the interface as small as possible, so that the
user can reach his goal in a very short time, even if he isn’t that familiar with
the task. The target button should also be as large as necessary so that the user
will find it comfortable to click on it. These two aspects are combined by the
Fitt’s law.
4
Human Memory
When we discuss the human as the central character in Human-computer interaction, then we also have to consider the human memory. We need to understand
the capabilities and limitations of the human memory in order to design our interactive systems in such a way that it will not overload user’s abilities. The
human memory can be divided into three different memories. In the next pages
we will discuss each of them in detail.
4.1
Sensory Memory
Information is transmitted through stimuli into our brain.There exists a sensory
memory for each sensory channel . This memory works as a buffer or collector
for stimuli through the senses. If the information that we received pass to the
short term memory depends on attention. Attention means that we filter the
information we got through the stimuli by arousal. Whereas arousal means the
level of interest or need we have. The arousal is a individual factor. Every human
has a different interest and different needs. The information will then be stored. If
it didn’t fit our arousal then it will be overwritten by new incoming information.
4.2
Short-term Memory
The short-term memory works like a scratch pad. That means that information
is temporary stored. For example when we want to multiply 35 and 6, we would
maybe first multiply 3 and 6 and get a intermediate result of 18, then we would
multiply 18 with 10 and get 180. After that we could multyply 5 and 6 and sum
up the result 30 with the 180 and get the end result of 210. So our brain would
store intermediate stages but after using the results we would likely forget them
again after a while. The information in the short-term memory are stored about
200 ms and if we want to recall information from this memory it would take
about 70 ms. The human short-term memory has also a limited capacity. For
example human are able to store a sequence of 7 +- 2 digits. We can store sequences when they are ordered or we can remember them better when we try to
group the sequence into parts. In contrary human beings can remember objects
or sentences in any order. For example we could group the digit 265734981 into
three parts of three digits 265 and 734 and 981. This grouping is called chunking
and it is used to optimize our short-term memory. When we can chunk something successfully then we call this procedure closure. the aspect of closure is also
useful when we design interactive systems. Imagine a cash machine. A customer
wants to get some money, he enters his card and his pin, chose the amount he
wants to withdraw and ends the transaction. Before he gets the money, he will
first get his card back. The interaction is designed in this way in order to avoid
information loss for the user. If the user gets the money before the card he would
likely forget to take his card because for him the transaction is finished when he
gets the money. That suggests that we should consider that we don’t overload
our user’s short-term memory.
If we want to store information from the short-term memory, we need to
pass it to the long-term memory by rehearsal that means, for example, through
repeating the information.
4.3
Long-term Memory
The long-term memory stores our complete knowledge, that means all facts we
know, our abilities to use something and our behaviour in special situations. This
memory has a nearly unlimited capacity. The information which we store here
will not be forgotten that easily and we can recall them at any time. The longterm memory consists of two parts, the episodic and the semantic memory. The
episodic memory is the memory of autobiographical events like places, times,
emotions and contexts. For example when we got our bachelor graduation or
our marriage or the death of a person, we store these information in our episodic
memory. The semantic memory is a collection of factual information and general
knowledge (meanings and understandings) of the world unrelated to our experiences. That means that we can answer simple questions like What is 2 + 2 ?
without remembering the event where we learned to add two digits. There are
different ways of storing the information in the semantic memory. One of them
is the so called semantic network. Semantic networks are based on hierachical
structures.
In Figure 3 we can see an example of a semantic network. We could for
example store information about dogs in a hierachy. Maybe we don’t know what a
BEAGLE is but we know it is a HOUND and a HOUND tracks, so the BEAGLE
will track too and so on.
Fig. 3. Semantic network for dogs
In this way we can achieve new facts about a unknown or maybe not complete
known object. That means that semantic networks represent the associations and
relationships between single items in a human’s memory. By designing interactive
systems we can make use of hierachies by using them in our implementations or
data structures. For example in the e-learning branch when it comes to the point
how we could design our software in order that the user will easily remember new
facts or learning by himself new concepts, we could use such hierachies which
will lead the user to associate new facts.
A very common model of knowledge representation in our memory is the
production model. The model describes how we use condition-action rules in
order to know how we can react in a special situation. These rules are stored in
our long-term memory. For example the rule : ¡IF dog is growling, THEN run
away!¿ could be stored in our memory. When we then meet a situation in which
we hear a dog growling, the situation would match the condition and as result
we would produce the action of running away.
5
Information Processing
There are three different processes in our long-term memory,remembering of
information, forgetting and information retrieval.
Remembering If we repeat the exposure with a stimulus or by rehearsal of
a piece of information then the information is transfered into the long-term
memory. The scientist Ebbinghaus performed experiments on how human can
optimize their information storage and he came to the conclusion that a increased
learning time and time spane increases the ability to remember the information.
This is called the total time hypothesis.
Forgetting But how can we loose information stored in our long-term memory again? There are two main theories about how human forget their stored
knowledge. The first theory is the theory of decay. Decay means that information can eventually be forgotten after a periode of time. The second one is called
the theory of interference and is based on two ideas, retroactive and proactive
interference. The first one states that older information is lost when we acquire
new information. The second one means the opposite. Old information break
through and interfere with the new information. For example when you moved
to a new house and by mistake you drive to the old house instead to the new
one because you are used to the old way home. Another point are emotional
factors. It is proven that we remember positive information better than negative
information.
Information Retrieval The last aspect of this chapter is information retrieval.
There are two types of information retrieval, recall and recognition. Recall means
that information is stored in our memory. For example how we can use a web
interface or a special application. Recall can be easier by providing cues for
remembering. These cues let us get the information very fast from the memory.
An example for such a cue is the use of categories of words which belong together
or images of special aspects. In contrary Recognition means that we recognize
things without storing them in our memory.
6
Human Thinking
The last aspect in HCI we will discuss in this paper, is how human can process
and manipulate information. The human is an unique information-processing
system. He is not like animals or roboters who are limited in their abilities.
Human are able to reason and solve problems. When we talk about the human
thinking, we have to consider these two aspects.
6.1
Reasoning
Reasoning means that we use our knowledge to draw conclusions or to infer
something new about the domain of interest we are thinking of. There are three
types of reasoning, deductive, inductive and abductive reasoning. In the paper
these types of reasoning are defined as following and explained by examples:
”Deductive reasoning means deriving logical conclusions from given premises.”
For example: If it is raining then the ground is dry. It is raining. Therefore the
ground is dry. ”Inductive reasoning means that we generalize from known cases
to cases which we haven’t seen before.” An example for this could be: If every
elephant that we have ever seen has a trunk, we infer that all elephants have
trunks. ”‘Abductive reasoning means that we can reason from a fact to the action
or state that caused it.” A possible example for abduction could be: Suppose
we know that Sam always drives too fast when she has been drinking. If we see
Sam driving too fast, we may infer that she has been drinking. The example
shows that abductive reasoning is unreliable. But normally people make their
explanations in this way until new evidence is supported.
When designing interactive systems we need to take care that we will not
cause confusion to our users. A user will think that an event is caused by an
action if the event always follows the action. And if we change something in the
system or the event is not related to the action, the user will make errors which
will maybe lead him not to use our system again.
6.2
Problem Solving
Human can find solutions to unknows tasks by using their own knowledge. This
aspect is called problem solving. But how do people solve problems? There are
many theories about problem solving. One of the theories was invented by the
scientists Newell and Simon in the 1970’s , the so called Problem Space Theory.
This theory was based on the idea that the human mind is a limited information
processor. This processor can be visualized like an automata with states and you
can use state transition operators to come from the initial state over several steps
to your goal. Heuristics are used to select appropriate operators to reach the goal.
For example the means-end analysis is a heuristic. There we compare the initial
state with the goal and try to reduce the distance between the both. Another
possibility to solve problems is to find an analogy to former problems. We map
our new problem to already known ones. We call this analogical mapping.
But while solving a special task the user can make mistakes. There are two
models of errors, slips and the mental model. Slips are errors which result from
changes in the context of skilled behaviour. As we said before if we change for
example the position of the abort-button of a window interface from left to right,
then unfortunately most of the users would click on the right side because they
are used to the right oriented position of the abort-button. So when we design
interactive systems we need to take care which changes we make and how we can
avoid error-prone behaviour of our users. The mental model is based on the idea
that human make errors when they understand a model, a situation or a system
wrong. So we have to think of how we can make our systems easy in order to
make it understandable for our users.
Finally we can say that for designing interactive systems we need to have
a good knowledge of the human thinking and its psychology. Every human is
individual and our goal is to provide computer systems for every kind of human
being.
7
Conclusion
In this paper we have seen that the human is an individual information-processing
system who receives information through senses. The major senses in human
interaction are vision, hearing and touch. Information is stored in the human
memory. There are three different memories, sensory, short-term and long-term
memory. When we store information just for a short time spane then it is stored
in our short-term memory. In contrary we store everything we know in our
long-term memory. From there information can be retrieved and can be used
for reasoning and solving problems. We have seen the limitations of the human
body and thinking. We discovered that understanding the human’s psychology
and thinking is a comfortable guide to create user-friendly interactive systems
in order to avoid errors or misunderstanding from the user’s side.
References
1. A. Dix, J. Finlay, G. Abowd, R. Beale (1998) Human-Computer Interaction, Chapter
1: The human
2. www.wikipedia.org
3. http://images.google.de/