Lecture 2: Human Interaction with Computers

Lecture 2: Human and Computer

• Human users interact with computers.
• The golden principle in Human-Computer Interaction (HCI) is that "people should come first".
• Users have different abilities: culture, cognitive abilities, experience, physical (age, hand size, height, strength, disabilities).

Why Understand Humans in HCI?

• Humans have limited information processing capacity.
• This has implications for design.
• Interacting with technology is a cognitive process.

Information Processing Model in Humans

• Perceptual: handling sensory input from the outside world (input/output).
• Memorization: memory, which controls actions.

The Perceptual System (Input)

• Vision
• Hearing
• Smell
• Taste
• Touch

Human Vision

• Central vision: focused area
• Peripheral vision: surrounding area (rods are important for night/low-light vision; insensitive to color).

Peripheral Vision Example

• Fixate on a central point.
• Letters/symbols around the point should be equally readable.

Legibility

• Clear text is required.
• Legibility depends on:
  • Size
  • Contrast
  • Typeface
  • Spacing

Readability

• Readability is about general content complexity.
• Guidelines for readable writing:
  • Keep it simple
  • Keep it short

Simplicity Example

• Bad example: complex sentence
• Good example: short, clear sentence

Short Example

• Bad example: lengthy description
• Good example: Concise and to the point.

Design Choices (Sounds)

• Attention: attracting attention to critical situations or process end.
• Status information: continuous background sounds convey status (e.g., progress monitoring).
• Confirmation: sound confirms an action (e.g., sound when a file is deleted).
• Navigation: changing sounds indicate user location (like in hypertext).

Reaction

• A visual signal takes 200 ms for reaction time
• An auditory signal takes 150 ms for reaction time
• Reaction time for a pain signal is 700 ms
• Combinations of signals can increase speed of reaction
• Practice improves reaction time.

Human Memory

• The ability to store and retrieve information.
• Mechanisms for memory function need to be studied (how does it work)
• Arbitrary lists require studying and understanding of memory (how do we remember?)
• Memory ability varies, so individuals also need to be studied in memory.

Memory Types

• Sensory Memory
• Short-Term Memory (Working Memory)
• Long-Term Memory

Sensory Memory

• Buffers for stimuli from the senses.
  • Sparkler Trail (iconic memory)
  • Stereo Sound (echoic memory)
  • Hot Surfaces (haptic memory)
• Properties
  • Continuously overwritten (buffer)
  • Information decay (~0.5 seconds)

Attention

• Asking someone to repeat an unheard question
• Cocktail Party Phenomenon

Short-Term Memory (Working Memory)

• Digit Span: e.g., 2653976208134
• Chunks Span: e.g., 265 397 620 8134
• Miller's Law: The capacity of short-term memory is approximately 7 +/- 2 items.
• Chunking: breaking up long strings of information into units. This makes remembering easier in short term memory.

Rehearsal

• Spending more time can eliminate the recency effect in memory
• Interference doesn't cause an entire loss of information

Long-Term Memory

• Properties:
  • Huge (or infinite) storage capacity.
  • Slow access time (0.1 second).
  • Slow (or no) decay of stored information.

Computer

• Computers are now embedded in many devices: mobile phones, cameras, cars, washing machines, dishwashers, alarm clocks, ATMs, copy machines.
• Computer systems are diverse and have input/output devices each impacting user interaction.
  • Input devices: text entry, pointing
  • Output devices: screen (small, large), digital paper.

Keyboard Types

• Gaming keyboards: designed for gamers, offer special macro keys, backlighting, configurable keys (often with mechanical switches for responsiveness in gaming)
• Virtual keyboards: software-based keyboards on screen; commonly used in smartphones and tablets.
• Projection keyboards: virtual keyboards projected onto flat surface.

Mouse Types

• Mechanical mouse: uses a ball and rollers to track movement (often corded, high-performance).
• Optical mouse: uses optics to track movement.
• Wireless mouse: uses wireless tech (IrDA, Bluetooth, Wi-Fi) for cursor control.

Five-Finger Input Devices

• Touchscreens often use a five-finger input method.

Scanner Types

• Flatbed scanner: uses a glass pane and moving optical array to scan documents or images.
• Handheld scanner: smaller devices to scan items (often use hand-held operation to scan; barcode scanners a type).
• Photo scanner: often used for photographs, needing higher resolution and color depth; some come with image editing software for restoration.

Future Input Mechanisms

• Computer Vision: Enabling computers to identify and understand objects and people in images and videos.
• Neural Language Processing (NLP): Applying machine learning to enable computers to understand and communicate with human language.
• Sensor Control: Measuring and monitoring physical, chemical, or biological phenomena.
• Internet of Things (IoT): A network of physical objects connected and exchanging data.

Computer Vision Devices

• Eye Gaze/Retina or Iris Scanner: A device to observe eye movement for functions in video games and smartphones
• Sign Recognition recognizes the movement of a player for functions in games or on tablets/smartphones.
• Fingerprint/Finger Scanner/Reader: Identifies individual's fingerprints

Sensor

• (There are several images depicting different sensor devices)

NLP (Natural Language Processing)

• Voice Scanner: Voice prints are stored and used to verify identity (but not very reliable).

VR (Virtual Reality)

• Virtual environments generated by computers allow user interactions with virtual objects via devices such as headsets, gloves, or headphones. It gives users an experience without having to perform the action.

Biometric Devices

• Biometrics: identifies people using biological features (e.g., fingerprints, eye cornea, facial structure).
• Types: face scanner, retina/iris scanner, voice scanner.

Face Scanner

• Identifies people based on face measurements (e.g., distance between eyes, nose, mouth).

Input Interaction Fields

• Security: Fingerprint recognition, iris recognition, face recognition.
• Search: By image, by voice.
• Disable people: Sign language recognition, Speech recognition, Foot mouse, Eye mouse.

Input/Output Interaction

• Examples of input/output interactions (images).

Categories of Output Devices

• Visual output: displays processed data as text, images, or video (e.g., monitors, projectors).
• Data output: provides machine-readable output (e.g., plotters, 3D printers).
• Print output: creates hard copies (e.g., printers).
• Sound output: produces sound (e.g., speakers, headphones).

Applications of Monitor

• Personal computing: monitors are used in everyday tasks
• Workstations: monitors are primary display devices in professional settings

3D Printer

• A device that produces three-dimensional objects.

Common Input Devices Examples

• Keyboards, mice, touchscreens, webcams, graphic tools, scanners, microphones, game controllers. Each device has its own specific purpose and usage.

Enhancing Biometric Input Safety

• Biometric devices use unique physiological tendencies (fingerprints, patterns, facial characteristics) for automatic identity confirmation. These serve as a safer alternative to conventional passwords and reduce unauthorized access.