ITEC 4130 HCI
Fall 2011
Midterm
Dr. Jim Rowan
Prepared by:
Jim Rowan
Rules for the take home midterm.
Submit your midterm by attaching the MSWord document to an email and emailing
it to me before Friday midnight.
You are allowed to use any reference material you deem necessary or worthwhile.
You are not allowed to discuss the questions on this midterm with your classmates
while taking the midterm.
Below each question use the amount of space you deem necessary.
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Knowledge in the head and knowledge in the world:
For the questions in this section consider the system image that a computer
presents to the user: the physical hardware along with the desktop (e.g., a Mac and
the Finder or a PC and Windows) Be sure to describe what the computer
configuration is whether it is a laptop, desktop, handheld, touch pad or something
else.
1) (3points) Give an example of a way in which the system requires knowledge in
the head rather than in the world. Describe it in a way that makes your example
clear to the reader (that’d be me). If needed include images or diagrams…
System description: I have chosen to use the 13 inch MacBook Pro laptop that I
carry around as the system that the next series of questions addresses.
Example: On a Mac (or PC running windows) desktop there is a great deal of
knowledge in the world… that was the beauty of the desktop metaphor invented by
Alan Kay while at XEROX PARC.
But it doesn’t work all by itself, it requires knowledge in the head. Someone using
the mouse on the desktop needs to know that the items found on the desktop are
there to be interacted with. Knowing that double clicking an icon causes it to be
opened is an example of that required knowledge in the head.
Example2 (not required): Another example of knowledge in the head is the way that
you can force a shutdown. If the machine is off pressing the power button starts the
machine. If the machine is on, pressing the power button puts the machine to sleep.
If the machine is on, pressing the power button and holding it down for 5 seconds
(not an intuitive thing to do) forces the machine to shut down.
2) (3points) Why do you think the designer made this decision?
There was the tradeoff made by the designer… much more operating system
complexity against providing the user with the desktop metaphor. The desktop
metaphor has a huge advantage over the command line interface by requiring much
less knowledge in the head in order to operate the computer. While there is a small
penalty that must be paid (in terms of required knowledge in the head) to enable
the user to take advantage of all the knowledge available on the desktop no longer
does the user need to remember what things are called and where they are stored.
Instead the user simply browses the interface hunting for that information.
3) (3points) Give an example of a way in which the system requires knowledge in
the world rather than in the head. Describe it in a way that makes your example
clear to the reader (that’d be me). If needed include images or diagrams…
As before on a Mac (or PC running windows) desktop there is a great deal of
knowledge in the world… that was the beauty of the desktop metaphor invented by
Alan Kay while at XEROX PARC.
The user needs to know that a mouse is used to move around a pointer that was
seen on the screen. The user needs to know that the things, the icons, seen on the
screen either contain other information (folders) or they are programs both of
which are activated by double clicking them.
But, as before, this is all knowledge in the head that the user needs to carry with
them.
The icons are either folders that hold other icons, they are documents that can be
opened and viewed by double clicking them or they are application programs that
can be started by double clicking them.
These three types of icons all have different shapes to indicate their types and they
all have names that appear under them. These shapes and the names are examples
of knowledge in the world.
4) (3points) Why do you think the designer made this decision?
For the relatively small price of learning how to point with a mouse, learning what
the icons mean and how to interact with them the user gains a huge advantage of
not having to memorize and reproduce the names of commands, the names of the
objects and the names and directory structures demanded of the user when using
the command line interface.
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Constraints:
5) (4points) Define physical, semantic, cultural and logical constraints.
(Note: This comes straight from the book so I’m not going to re-type it)
6) (1point) Give an example of a constraint provided by the system (Note: here is
where I should have written “mentioned in question 1 above”). Is it physical,
semantic, cultural, or a logical constraint? Describe it in a way that makes it clear to
the reader (that’d be me) what type it is and why it is of that type.
(Note: In this question you only needed one example but I have chosen to include
examples of all 4 constraints just because I can…)
(Note: This is a reference I used to get ideas for an example:
http://katsvision.com/canm606/session_3/03_norman_01.pdf )
Physical constraint:
General examples not related to the Mac system:
In modern automobiles with stick shifts you cannot start the car unless the clutch is
depressed.
My favorite: (from the above reference): A manhole cover is round so that you
cannot drop it through the hole and kill the guy down there.
The example from the Mac:
You cannot hook the power cable to any other connector or put it in any other
opening except where it actually goes. By the nature of it’s rectangular shape it is
also constrained to allow the power connector to allow the power cable to come
towards you or away from you but not up or down.
Semantic constraint:
A general example not related to the Mac system:
In a room full of backless benches everyone faces in the direction of the wall that has
a blackboard on it… it’s a classroom.
The example from the Mac:
Which side is up? With 4 rubber pads on one side (clearly feet) and an apple logo on
the other it is semantically constrained to be opened with the apple logo visible, on
top.
Interesting side note:
Look at which direction the apple logo faces when closed. (it faces away from you…
it’s upside down) Look at the position of the apple logo when opened. (it is right side
up to those who can see it).
This has not always been the case.
On earlier Mac notebooks the apple was right side up (to the user) when closed. To
me this makes sense because the user is who the machine is designed to be used by.
When oriented this way however, in use the apple logo was upside down to
everyone who could see it (which was fine by me since it was my machine and I
didn’t really care what other people saw). By changing it to the more current
orientation it becomes a billboard for Mac.
Cultural constraint:
General examples not related to the Mac system:
A black ribbon tied to the mailbox announces a death in the family.
A blue ribbon tied to the mailbox announces a birth of a boy in the family.
A pink ribbon tied to the mailbox announces a birth of a girl in the family.
The example from the Mac:
When the battery level gets low the battery icon in the menu bar turns red, red
being the cultural color for warning.
Logical constraint:
A general example not related to the Mac system:
You are putting together a toy and there are 4 large bolts, 4 large nuts and 4 large
holes while there are 3 smaller bolts, 3 smaller nuts and 3 smaller holse. There are
also 4 washers. The 4 bolts, washers and nuts are to go in the 4 holes.
The example from the Mac:
The caps lock key has two states set and not set. This is the only key on the 13 inch
MacBook Pro that has two states. These states (or modes) are shown with an LED on
the key. If it is locked, the light is on and green indicating that it is in the cap lock
setting. If it is not locked the light is off and it looks like a white spot on the key.
There are no other keys with the white spots so I can assume that it is the only
lockable key. Note: It does not have an numloc key like some of the larger models
have.
I’m not completely satisfied with the above answer so I’ll entertain arguments pro
and con if you are interested… in the mean time there are only 2 USB ports which
logically constrains the addition of only two USB devices at a time (well, unless you
get a USB splitter)
7) (1point) Other than the trash can (the garbage, the wastebasket) give an
example of a way in which the system prevents errors or helps the user to recover
from errors.
(just to be clear… the trash can that I excluded above prevents errors by not actually
throwing items away that are tossed into the trash)
There are a ton of these:
Try to empty the garbage can and you get a warning dialog box.
Try to close a document and you get a warning dialog box.
You can encrypt your home files and you get a warning that if you forget your
password you are screwed.
Use “secure empty trash” and you get a warning that nothing can be recovered.
8) (3points) Find and describe examples of the three other constraints of a type
NOT described above. Describe them in a way that makes it clear to the reader
(that’d be me) what type they are and why they are of that type. If needed include
images or diagrams…
(See #6 above)
N(ote: These constraints do not have to be about the system described in #1 above)
Mappings:
8or9) (2points) Don Norman talks about natural mappings and how they associate
the available controls to the possible actions. Find, photograph and include (below)
two examples; one example of a particularly bad mapping and one example of a
good mapping. These examples should be found in your world, not from the Internet
or the texts and they should not be examples seen in class this semester. Describe
each in a way that makes your example clear to the reader (that’d be me) through
images, diagrams, descriptive text and what ever else you deem necessary. In your
description be sure to tell me where these examples were found.
OOPS! Two number 8s! OhHell…OhWell…
(So here is where I cheat. I’m going to use the ones I’ve posted on the wiki as
examples)
Good mappings:
The mirror control of this Honda is nearly a perfect mapping to the mirrors.
The top switch selects and adjusts the left and right mirrors and the switches are in
the same plane as the mirrors. Looking at the selector switch (the top switch) you
can see that moving the switch to the left selects the left mirror and moving the
selector to the right selects the right mirror.
The lower rockingswitch is in the same plane as the mirrors so it is nearly perfectly
mapped since pushing the top of the lower switch moves the mirror in the same
direction as reaching through the window and pushing on the top of the mirror. The
same is true of the bottom, the left and the right of the switch.
Bad mappings:
The mirror controls in this BMW are not so perfectly matched as the Honda.
The controls are on the handle that is used to close the door and they are not in the
same plane as the mirror. The small switch is the selector switch and moves up and
down. The large switch is the mirror movement switch.
To move the mirrors you first have to select a mirror. The choices are forward and
backward… does forward select the left or to the right? It turns out that forward
selects the right mirror and backward selects the left mirror. A way to remember
how it works is to have a mental model that maps the movement of the switch to the
movement of the turn signals. With that mental model it’s not hard to remember.
The mirror movement switch is more closely mapped to the movement of the
mirrors but it isn’t as perfect a mapping as the Honda. You have to imagine that the
switch is in the same plane as the mirrors and that pushing the switch forward
(think moving it up) is like pushing on the top of the mirror. It’s a bit more indirect
than the Honda but easy enough to remember.
_
The window controls on this car are in the center console. The one on the left moves
the window on the left, the one on the right moves the window on the right. This is a
bit distant from the device that it is controlling… usually it is wiser to put the switch
closer to the device it operates.
To make the windows go up you push the front of the switch and pushing the back
of the switch makes the window goes down. The user has to keep a model of the
switch that relates front to top and back to down… not to hard to do if you transpose
the position of the switch so that it is in the same plane as the window it operates.
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Affordances:
9or10) (5points) The highway department is considering constructing a partially
enclosed shelter in which vending machines will be placed. These shelters will be
located along the highway at unmanned rest stops every 20 miles or so. While the
support structure and the roofing are already contracted, various materials for the
sidewalls are being considered. One is heavy tempered glass, another is a wood
panel product similar to plywood and the third is a heavy polycarbonate (clear
plastic sheeting). What are the affordances of each of these that relate to their
intended use that might affect this choice? Make sure to include the context of use
and user profile in your discussion.
Context of use: The intended context of use here is to provide a place for venders to
put their vending machines in. These vending machines are meant to serve the
traveling public using the highway system, both private and commercial users.
User profile: The user profile is the very broadest of profiles in that it includes
anyone who uses the highway system for transport. This will include all manner of
people, civilians traveling on vacation, truck drivers of commercial transport as well
as criminals, law enforcement and the military.
The intended use of these panels is to form a shelter that will block the wind and
provide a shelter and protection for the vending machines as well as provide a
temporary safe haven for the people using the machines. Putting cost aside, each has
advantages and disadvantages.
The glass, polycarbonate and the plywood all provide protection against the
elements.
The glass and polycarbonate both allow outside light in and might reduce the need
for lighting during the day, although at night they both would need lights.
Additionally both of these give the vending machines better visibility making it
easier for the intended user to locate the machines.
Plywood can be painted to match or contrast the other buildings in the rest stops
while the glass and polycarbonate cannot.
Glass is breakable while polycarbonate isn’t.
Plywood and polycarbonate are also susceptible to being burned and might
contribute to a structure fire.
10or11) (5points) What are the affordances of each of these that do not relate to
their intended use (remember that humans are opportunistic and creative) that
might affect this choice? Make sure to include the context of use and user profile in
your discussion.
Context of use: The context of use here is the same as the question above but the
user profile is greatly narrowed to vandals and possibly criminals.
Glass can be broken and seems to be one of the vandal’s favorite things to break.
Though it would be tempered and very difficult to break, it will break with enough
effort.
The visibility of both glass and polycarbonate might allow the criminal to assess his
target (perhaps just elderly people are using the machines and they would make
easy targets) or see if there is law enforcement present.
All three of these panels lend themselves to being tagged or having handbills pasted
to them.
The plywood can be cut with a knife and things can be carved into it.
The polycarbonate can be scratched with a knife blade and would afford a really
nice surface to mark up and leave unsavory messages to anyone who might be
unfortunate enough to read them.
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Slips and Mistakes:
11or12) (2points) Giving an example of each (but not an example found in DOET,)
describe how slips and mistakes differ.
Humans frequently make mistakes and Don Norman categorizes them as two
different types.
Mistakes occur when we successfully carry out an action that is completely wrong
from the beginning. Mistakes differ from slips because there is no chance for taking
corrective action or providing support in order to prevent the mistake because we
do not know that we are doing the wrong thing.
Slips are different than mistakes because with slips we know what the correct set of
actions are to carry out a task but somewhere along the way we foul up the action.
With slips there is a hope of recognizing that an error was made which allows the
possibility of either providing support to prevent the slip in the future or taking
some kind of corrective action.
12or13) (6points) Don Norman describes 6 different types of slips.
Describe these in a way that makes the differences clear to the reader (that’d be me)
and provide an example of each (but not an example found in DOET).
Capture: In the process of carrying out some action you get to a point in the
execution that is very similar to some other point in some other action. Suddenly
you find yourself completing the first action with the completion actions of the
section action.
Example1: I was using a copying machine, and I was counting the pages. I found
myself counting "1, 2, 3, 4, 5, 6, 7, 8, 9, 10, Jack, Queen, King."
(Above example from Don Norman’s 1981 Psychological Review article found at:
http://ocw.tudelft.nl/fileadmin/ocw/courses/IntelligentUserExperienceEngineerin
g/res00119/!385f43617465676f72697a6174696f6e206f6620616374696f6e20736
c697073.pdf)
Example2: Just today this happened. I come to campus and park half way between
building A and building B. When I return to the car in the afternoon I open the
passenger door, take off my pack and put it in the front seat followed by putting my
drink in the drink holder. Then I walk around the car and get in. Today I decided
that I don’t need my coat any longer so I stopped by my car on the way from one
building to the next. I walked up, opened the passenger door and put my pack in the
front seat when my intention (earlier on the way to the car) was to put the coat in
the front seat.
Description: Description errors occur when the completion of one task has a lot in
common with the completion of some other task. Given that, and an underspecified
final action, you have two final actions that look the same.
Example: I’m grinding the coffee beans for the morning coffee. I usually get my
coffee cup out of the cupboard and place it at one end of the kitchen island but this
morning I get it out of the dishwasher and set it on the counter next to the stove. I
get out the beans and grinder I keep next to the stove along with the coffee press.
When I’ve finished grinding the coffee beans for the morning coffee I dump the
grounds into my coffee cup and not the press. The coffee press and the coffee cup
has a similar mental description: things that receive coffee.
Data-driven: When information found in your environment affects your carrying out
a familiar task resulting in an incorrect completion of the task.
Example: The most prominent example is the Stroop phenomenon, a classic
demonstration experiment in psychology in which the names of colors (e.g., blue)
are printed in colors that differ from the name (so that the word blue might be
printed with red ink). The task is to look at the word as rapidly as possible and say
aloud the name of the ink color in which it is printed. There is extreme difficulty
caused by the intrusion of the printed names.
NOTE: The example above is from Don Norman’s 1981 Psychological Review article
found at:
http://ocw.tudelft.nl/fileadmin/ocw/courses/IntelligentUserExperienceEngineerin
g/res00119/!385f43617465676f72697a6174696f6e206f6620616374696f6e20736
c697073.pdf
Associative activation: There is a strong association between two action sequences
resulting in the incorrect sequence taking control over the action sequence under
way. These most frequently occur in speech.
Example: I have lived in Alabama and Georgia and both states have strong football
rivalries. Alabama has Auburn (where I went) and Alabama, the archrival. Georgia
has Georgia Tech (where I went) and UGA. In both cases I guess I basically think of
them as the engineering school and the lawyer school. I’ll be meaning to say UGA but
I instead I say Alabama… uh… UGA.
Loss-of-activation: This is what my friend calls destinasia… you head out to do
something, you maintain your knowledge of where you are going but when you get
to where you need to be you have forgotten why.
Example: Working in the upstairs bedroom you go to the garage to get a measuring
tape and when you get there you know that you are in the right place but you can’t
remember what you wanted to get.
Mode error: This is when an error occurs because the system you are working with
is not telling you that it is doing one thing while you think it is doing something else.
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Human cognition:
13(or14) (1point) With practice, cognitive activities can become automated. This
has performance advantages in that responses are fast and require little or no
conscious attention. There are, however, a number of disadvantages that are
associated with these automated cognitive processes that can lead to error. Describe
1 of these, providing an example.
Description: Two well-practiced cognitive processes that are similar in their
initiation but differing in their completion can interfere with one another, especially
if the one more well practiced process has been replaced with the slightly less
practiced one. The problem rises when performing under pressure. Under pressure
it is not unusual for the more practiced process to take control over the more
recently learned, slightly less practiced process.
Example: I drive the same car with a stick shift most of the time. To start the car I
need to press the clutch before turning the key. This becomes an automated process.
Once a month (or so) I drive the other car that has an automatic. Invariably I will
stomp the floor with my left foot before I turn the ignition.
14(or15) (2points) Giving an example of each what is the difference between
declarative and procedural knowledge?
Declarative knowledge: Things that have to be memorized like lists and facts. There
are a number of tricks (like pneumonics) that make it easier. These are facts that
you might put on flash cards in order to memorize. Jeopardy champions are the
kings of this world.
Procedural knowledge: This is knowledge of “how to.” Things that have to be
practiced like riding a bicycle. Generally they cannot be described as easily as they
can be demonstrated. Apprenticeships work well as a means of developing these
skills. Athletes, dancers and welders are the kings of this world.