Exam Revision
Final examination
• October 26 2021 between 14:00 and 17:15 (Australian Eastern Standard Time)
• No submission will be accepted after October 26 2021 at 17:30
• The portal of the exam is on the LMS
Exam Revision
• The exam paper comprises 32 questions of 4 sections. Marks total 140.
• 1. Multiple Choice Questions (at least one answer): 20 questions with 2
marks for each
• 2. Short Answer Questions: 7 questions with 5 marks for each
• 3. Interaction Analysis: 2 questions with 10 marks for each
• 4. Interaction Design: 3 questions with 15 marks for each
• Most questions asks to discuss various things.
• Key factor tested is understanding.
• Make sure you have read through all lecture notes and done all the labs
• Exam questions are not only limited to the topics discussed in the
following slides.
Some tips for you
• Review the lecture notes and labs
• Allocate your time according to questions’ mark
• Read questions carefully.
• Try to answer each question as possible.
• Zero mark if you do not write a word for a question!
• Good luck!
* means important chapters.
Introduction *
• Definition of HCI
• Multidisciplinary field
• Batch interface, Command-line user interface, Graphical User Interface
• Interaction tasks
• Properties of input devices
• Absolute vs. relative input devices
• Direct vs. indirect devices
• Transfer function
• Three-state model
• Degrees of freedom
Human-computer Interaction (HCI)
• Human-computer interaction is a discipline concerned with the
design, evaluation and implementation of interactive computing
systems for human use and with the study of major phenomena
surrounding them.
• ACM SIGCHI Curricula for HCI (Hewett et al. 1992)
• http://sigchi.org/cdg/cdg2.html
7
Design
Computer Science
Sociology
Applied Psychology
Interaction Tasks
• Selection: Choosing objects from a set of
alternatives
• Position: Specifying a position within a
range. This includes picking a screen
coordinate with a pointing device.
• Orient: Specifying an angle or three-
dimensional orientation.
Interaction Tasks
• Path: Specifying a series of positions
and/or orientations over time.
• Quantify: Specifying an exact numeric value.
• E.g. scale widget
• Text: Entry of symbolic data.
Properties of Input Devices
• Sense position
• Tablet
• Sense motion
• Mouse: change in position
• Sense force
• Isometric joystick
Absolute vs. relative input devices
• Absolute
• 1-to-1 mapping between input and output space
• Example: position sensing devices like tablet
• Relative
• Input controls the relative position of the cursor (always indirect)
• Example: motion sensing devices like mouse and touch pad
Direct vs. indirect control
• A mouse is an indirect input device (the display surface is not the
input surface);
• one must move the mouse to point to a spot on the screen
• a touchscreen is a direct input device (the display surface is also the
input surface)
Direct vs. Indirect Devices
• Direct input
• Hovering feedback is not indispensable as there is a clear mapping between
pen/fingers and the screen
• Main drawback: occlusion problems
• Indirect input
• Hovering is indispensable: users must know the position of the cursor before
starting drawing
Transfer function
• An appropriate mapping is a transfer function that matches the
physical properties sensed by the input device.
• force-to-velocity: isometric joystick
• position-to-position: touchscreen
• velocity-to-velocity functions: mouse, touchpad
• For example, an isometric joystick senses force; a nonlinear rate mapping
transforms this into a velocity of cursor movement
Control-to-Display (C:D) ratio
• Simple multiplicative transfer function (known as the device gain)
• The ratio between the movement of the input device and the corresponding movement
of the object it controls.
• For example, if a mouse (the control) must be moved 1 cm on the desk in order to move
a cursor 2 cm on the screen (the display), the device has a 1:2 control-display ratio
• On commercial pointing devices and operating systems, the gain is rarely constant; an
acceleration function is often used to modulate the gain depending on velocity
Input Device States
• Three-state model
Degrees of Freedom
• Degrees of freedom = the number of parameters that may vary
independently
• Conventional GUI is largely based on moving around a single 2D
cursor (x, y), using a mouse, for example. This results in 2DOF.
• One touch point can control the X and Y position of an
object (2 degrees of freedom)
• Sensing the location of two fingers: 4DOF
• Two touch points can control the X and Y position of an
object, its rotation, and its scale
Mouse and Keyboard
• Types of mouse
• Properties of mouse
• Types of keyboard
• Properties of keyboard
Types of Mouse
• According to the working mechanism a
mouse can be two main types:
• Mechanical
• This is a type of computer mouse that has a
rubber or metal ball on its underside and it can
roll in every direction.
• Optical
• Optical mouse has a small and red light-emitting
diode (LED) that bounces light off that surface
onto a (Complementary metal-oxide
semiconductor) CMOS sensor.
Properties of the Mouse
• Sense motion
• Relative input device
• Input controls the relative position of the cursor
• Control and Display Ratio (CD ratio)
• Three-state Model
• Indirect input device
• one must move the mouse to point to a spot on the screen
Category
• Mechanical keyboard
• Touch screen soft keyboards
• Stylus-driven soft keyboards
• Three-state Model
State
0
State
1
State
2
Touch Press
Release Release
How about touchscreen keyboards?
Hold
Three-state Model for touchscreen keyboards
State
0
State
1
Touch
Release
Hold
Skill Acquisition and Skill Transfer
• Procedural memory is a specific type of memory that encodes
repetitive motor acts.
• Once an activity is encoded in procedural memory, it requires little
conscious effort to perform.
• The process of encoding an activity in procedural memory can be
formalized as the power law of practice: T = aPb, where T is the time
to perform the task, P is the amount of practice, and a and b are
constants that fit the curve to observed data.
• Changing the keyboard can have a
high re-learning cost
Eyes-Free Operation
• With practice, users can memorize the location of commonly used
keys relative to the home position of the two hands, allowing typing
with little or no visual attention
Tactile Feedback
• Mechanical keyboard
• Touchscreen keyboards
Experiment Design and Data Analysis *
• Experiment design process
• Independent variable vs. Dependent variable
• Control variable, random variable, confounding variable
• Within-subjects design vs. Between-subjects design
• Latin Square
• Likert scale
Experiment design process
• Refer to lab 3
Variables
Pen is faster than
finger
1. Independent
variable:
Device (Pen
and Finger)
2. Dependent
variable: Speed
Relationships
Pen is faster and
more accurate
than finger
1. Independent
variable:
Device (Pen
and Finger)
2. Dependent
variable:
Speed,
Accuracy
Control Variable
• A control variable is a circumstance (not under investigation) that is kept
constant while testing the effect of an independent variable
• More control means the experiment is less generalizable (i.e., less
applicable to other people and other situations)
• Research question: Is there an effect of font color or background color on
reading comprehension?
– Independent variables: font color, background color
– Dependent variable: comprehension test scores
– Control variables
• Font size (e.g., 12 point)
• Font family (e.g., Times)
• Ambient lighting (e.g., fluorescent, fixed intensity)
• Etc.
Random Variable
• A random variable is a circumstance that is allowed to vary randomly
• are assumed to be values that are drawn from a larger population of values and
thus will represent them.
• More variability is introduced in the measures (that’s bad!), but the results are
more generalizable (that’s good!)
• Research question: Does user stance affect performance while playing Guitar
Hero?
– Independent variable: stance (standing, sitting)
– Dependent variable: score on songs
– Random variables
• Prior experience playing a real musical instrument
• Prior experience playing Guitar Hero
• Amount of coffee consumed prior to testing
• Etc.
Confounding Variable
• A confounding variable is a circumstance that varies systematically with an
independent variable
• Should be considered, else the results are misleading
• Research question: In an eye tracking application, is there an effect of
“camera distance” on task completion time?
– Independent variable: Camera distance (near, far)
• Near camera (A): inexpensive camera mounted on eye glasses
• Far camera (B): expensive camera mounted above system display
– Dependent variable: task completion time
– But, “camera” is a confounding variable: camera A for the near
setup, camera B for the far setup
– Are the effects due to camera distance or to some aspect of the
different setups?
Within-subjects, Between-subjects
• Two ways to assign conditions to participants:
– Within-subjects -> each participant is tested on each condition
– Between-subjects -> each participant is tested on one condition only
– Example: An IV with three test conditions (A, B, C):
Latin Squares
Questionnaire
• Personal information
• Likert scale
• E.g. Gesturing speed with dominant thumb
Slow 1 2 3 4 5 6 7 Quick
• questions
• Suggestions, advices
HCI Tasks and Models *
• Pointing Task
• Crossing Task
• Steering Task
• Gesturing Task
• Tracing Task
Basic HCI Tasks
• Pointing Task
• Crossing Task
• Steering Task
• Gesturing Task
• Tracing Task
Human Factors
• Sensors
• Vision
• Hearing
• Touch Smell and taste
• Responders
• Limbs
• Voice
• Eyes
Interaction Elements *
• Hard controls and soft controls
• Control-display relationships
• Modes
• Degrees of freedom
Hard Controls, Soft Controls
• In the past, controls were physical, single-purpose
devices à hard controls
• Today’s graphical displays are malleable
• Interfaces created in software à soft controls
• Soft controls rendered on a display
• Distinction blurred between soft controls and
displays
• Consider controls to format this (see below)
42
Soft controls are also displays!
Example: Scrollbar Slider
• Example of a soft control (control + display)
• As a control
• Moved to change view in document
• As a display
• Size reveals view size relative to entire document
• Position reveals view location in document
43
Control-Display Relationships
• Also called mappings
• Relationship between operation of a control and
the effect created on a display
• At least three types:
• Spatial relationships: an exact spatial correspondence
between the controller input and the display output
• Dynamic relationships: how a controller affects the
speed of the response
• Physical relationships: whether the response is to a
movement or a force in the controller
44
Spatial Relationships
45
Spatial congruence
Control: right
Display: right
Spatial transformation
Control: forward
Display: up
Natural
Learned
Axis Labeling
46
Control
Display
CD Gain and User Performance
• Tricky to adjust CD gain to optimize user performance
• Issues:
• Speed accuracy trade-off (what reduces positioning time tends to
increase errors)
• Opposing relationship between gross and fine positioning times:
47
Modes
• A mode is a functioning arrangement or condition
• Modes are everywhere (and in most cases are
unavoidable)
• Office phone light: on = message waiting, off = no
messages
• Computer keyboards have modes
• »100 keys + SHIFT, CTRL, ALT è »800 key variations
48
Mode Switching
• PowerPoint: Five view modes
• Switch modes by clicking soft button
• Current mode apparent by background shading
• Still problems lurk
• How to exit Slide Show mode?
• PowerPoint à ESC
49
Modes and Degrees of Freedom
• If control DOF < display DOF, modes are necessary to fully access the display DOF • Consider a mouse (2 DOF) and a desktop display (3 DOF) • x-y control (no problem): 50 but… Gesture Interaction * • Properties of gesture interaction • Gesture category • Learning-memorization • Time predication formula(CLC model) • Gesture recognition algorithm:$1 Properties of Gesture Interaction • Memory-driven • Error-tolerant • Muscle memory • Button-free • Eyes-free • Touch Gestures • 2D gestures • Motion Gestures • 3D gestures Gesture Category 1 2D Gesture • Single Stroke Gesture • Multi Stroke Gesture Gesture Category 2 • Analogue Gestures • Flick gesture • Abstract Gestures • Draw X to close a window Learning-memorization Solution: 1. Marking Menu 2. Gesture Bar 3. User-defined gestures Time Predication Formula(CLC model) Gesture recognition algorithm:$1 Prototype Gestures A Drawn Gesture Resample Rotate Scale and Translate Scale Translate Recognize Center PointCalculate the average shape distance between the drawn gesture and the prototype gestures, and find the smallest one Distance(T, drawn_gesture) d Pen Interaction * • Properties of pen input • Sensors for pen input detection • State Transaction • Mode Switch • Pen Properties Properties of pen input • Absolute input device: 1-to-1 mapping between input and output space • Direct input device: the display surface is also the input surface Sensors for pen input detection Resistive Screens Sensing that pressure is being applied Capacitive Screens: Sensing the conductive properties of an object, usually the skin on your fingertip CAPACITIVE SCREEN State Transaction Assume a graphics tablet with stylus. In State 0, the stylus is off of the tablet and the tip switch in its open state. Moving the stylus has no effect since it is out of range. When the stylus is in range, the tracking symbol follows the stylus' motion (State 1: tracking). Extra pressure on the stylus closes the tip switch, thereby moving the system into State 2. Mode Switch • Inking • Gesturing Pen Properties • (x, y) coordinate • Pen pressure • Pen Tilt • Pen rolling • Pen azimuth Pen Rolling Pen Tilt Pen Pressure Pen Azimuth North EastWest South Touch Interaction * • Sensors for finger input detection • Touch screen vs. touch pad • Degrees of freedom • State model • Finger properties • Limitation of finger input Sensors for finger input detection Resistive Screens Sensing that pressure is being applied Capacitive Screens: Sensing the conductive properties of an object, usually the skin on your fingertip CAPACITIVE SCREEN Main Type for Finger input Touch screen vs. Touch pad Factor Touch screen Touch pad Precision Low (fat finger problem) High (same as mouse) Object state Two-state model: the touch surface of a display device is either touched (on) or not (off). There is no hover state that can trigger additional visual feedback. Same as touch. Rich interaction Supports multi-touch: multiple input points (fingertips) on a touch surface. Same as touch. Supports direct manipulation of objects through gestures such as tapping, dragging, sliding, pinching, and rotating. No support for direct manipulation as they are indirect input devices. Degrees of Freedom • Conventional GUI is largely based on moving around a single 2D cursor (x, y), using a mouse, for example. This results in 2DOF. • Sensing the location of two fingers: 4DOF Holding Postures • Mobile phones and tablets State model Finger Property • X, Y • Orientation • Contact Area • Finger Pressure Fat Finger Solutions? Feedback • The nature of feedback • Visual feedback • Audio feedback • Tactile feedback • Olfactory feedback • Thermal feedback Feedback in HCI • The communication of the state of the system, either as a response to user actions, to inform the user about the conversation state of the system as a conversation participant, or as a result of some noteworthy event of which the user needs to be apprised. • Renaud, K., Cooper, R.: Feedback in human-computer interaction: Characteristics and recommendations. In: South African Institute of Computer Scientists and Information Technologists. Annual Research Conference, Cape Town, South Africa(2000), pp. 105-114 The nature of feedback • Signalling a response - satisfied by immediate feedback; • Changing behaviour, and promoting understanding - satisfied by both immediate and archival feedback. • Immediate feedback allows the user to judge the immediate state of the system • Archival feedback would allow them to obtain a deeper understanding of how the system arrived at that state over a period of time; Eye Interaction • Eye trackers • Applications of eye input • Advantages of eye input • Limitations of eye input • Solutions to address eye input limitations Eye Trackers Remote eye tracker Head mounted eye tracker Eye Tracking Techniques 1: Video-Based Tracking Eye Tracking Techniques 2: Electrooculography-Based Tracking Applications of eye input • Target selection • Eye tracking heatmap • Text entry Advantages of eye input • Good for quadriplegics • Easy to reach remote targets Limitations of eye input • Midas-Touch • lack of analogous functions for single-clicking • Limitations in tracking accuracy, calibration errors and drift • The inherent jittery motions of the eyes Solution? Q&A