Human-Computer Interaction

Introduction to Human-Computer Interaction Lecture 1

What is HCI:- The study of people, computer technology and the way they influence each other. HCI is the discipline concerned with the design, evaluation, and implementation of interactive computing systems for human use.

Aim of HCI:- To make technology more usable by people. Requires understanding of:- people technology what is meant by usable tasks people perform using technology Multidisciplinary:- Computing, Cognitive Science, Psychology, Sociology

Some applications:- Internet Web page design / E-commerce / E-government Intranet Organizational and Social aspects Interactive TV Improve performance (why do users give up) Mobile devices Real-time access, small screen & high density Kiosk & Digital Libraries Quick and Easy access to information

Why study HCI:- • The interaction is the means of how people come into contact with computer systems. • Hardware is cheap, software and people are expensive.

Foundations: The Human Factor Part 1 Perception Lecture 2

Human information processing:- is a flow of information between various input devises, information stores, transformationnel processes and output devices. The three main stages of information processing are: Perception encoding, Central processing, and Responding Perception encoding includes the five senses: sight, hearing, touch, smell, taste.

Input-output channels Senses:- Sight, Hearing, Touch, Taste, Smell Effectors:- Limbs (members), Fingers, Eyes, Head, Vocal (speaking) system

Question? Imagine a user using a PC with a mouse and a keyboard. List sensors and effectors used in two types of applications: An application with a standard GUI (menus, icons, windows). An interactive voice mail system.

GUI Senses: Sight is mainly used. However, hearing can also be used. Touch plays an important role too because the user feels the pressing of a key or the mouse button as well as the movement of the mouse. In this case the user is aware of what he/she has done. Taste and smell are not used. Effectors: Hand (hitting keys or moving the mouse) Voice mail Senses: Hearing is mainly used. However, sight also plays an important role (can give awareness that the user is doing something wrongly). Touch is less important. Taste and smell are not used. Effectors: vocal system, hand (less frequently).

Vision Visual perception is divided into two stages: 1. Physical perception of the stimulus (light). 2. Processing and interpretation of the stimulus.

Visual angle Visual angle depends on the size of the object and the distance of the object from the eye.

Color:- Uses To label To measure To separate To represent or imitate reality To stimulate or decorate

Perceptual dimensions of color:- Hue determined by the spectral wavelength of the light. Intensity the brightness of the color. Saturation the amount of whiteness in the color.

Contrast: Luminance vs. color:- Luminance :- the amount of light emitted (produced) by an object, depends on the amount of light falling on the object and its reflective properties Contrast:- is a function of the luminance of an object and the luminance of its background.

Foundations: The Human Factor Part 2 Memory Lecture 3

Memory types:- Sensory memory Acts as buffers for stimuli received through senses Short-term memory Acts as a “scratch-pad” for temporary recall of information Long-term memory The repository for knowledge

Sensory memory:- Iconic memory For visual stimuli Echoic memory For aural stimuli Haptic memory For touch

Short-term (working) memory:- Limited capacity . Rapid recall of information. Rapid decay. Rate of decay influenced by amount of information being stored and attentional resources available for rehearsal.

Chunking: Grouping together of several bits of information into a single entity. Patterns & using various sensory channels can aid chunking & remembering.

Working memory: chunking:- Chunks are defined by physical and cognitive properties that bind items together. Number of items that can be stored is reduced as chunks get larger. But amount of data that is stored in working memory is increased. Fewer items stored, so they are more easily rehearsed & transferred to long-term memory. Makes use of meaningful associations in long-term memory, aiding the retention of information.

Working memory: decay:- Rate of decay increases as more chunks are stored in working memory. It increases also when attentional resources are added. Multi-tasking

Working memory: implications:- Minimize working memory load Provide visual signals Exploit chunking Minimize confusability (distinct elements) Exploit visual-spatial and verbal-phonetic codes

Long-term memory:- Everything we “know” Declarative knowledge (factual information) Experiential knowledge Procedural knowledge (rules) Almost limitless capacity. Relatively slow access time. Interference: New information unintentionally replaces old. Consistent interfaces produce less interference between applications.

Long-term memory: structure:- Information is stored with some structure that defines ways in which pieces of information relate to each other. Allows information to be stored & retrieved efficiently. Understanding people’s mental models, explanation & theories of human behavior.

Recall vs. Recognition Recall: Information has to be remembered, e.g., the name of a command that has to be typed. Recognition: The information is provided and all a person has to do is choose it (e.g., select an option from a menu). Reduced cost, providing the information can be easily recognized.

Foundations: The Human Factor Part 3: Human Reasoning Lecture 5

Types of human reasoning Reasoning is the process by which we use the knowledge we have to infer something new about the domain of interest Deductive reasoning derives logically necessary conclusions from given premises Inductive reasoning generalizes from cases we have seen to infer information about cases we have not seen. Abductive reasoning reasons from a fact to the action or the state that causes it.

Deductive reasoning:- Logical reasoning modus ponens: (p=>q, p) => q If it rains then the road is wet. It rains today. Therefore: the road is wet. Belief bias Some people are babies. Some babies cry. Therefore: some people cry. Some English speak Spanish, Some Spanish live in Mexico, Therefore: Some English live in Mexico Deductive reasoning: examples Interface type All textual interfaces require typing commands. Linux has a textual interface. Therefore: Linux require typing commands. Exit option All programs must have an exit option. Therefore: the software I work with should have an exit option. Implications to interaction design Software/platform consistency.

Inductive reasoning:- Inductive reasoning examples:- Most birds fly. Penguin is a bird. Therefore: the penguin flies . Interface widgets Tool bars: Copy/Paste/Print Short keys Ctrl-V (but Ctrl-Y) Ctrl-X (but Ctrl-K)

Abductive reasoning::- Abductive reasoning: examples Using a new program Trial and error; assumptions; inferred explanations (which sometimes could be wrong!) The broken printer example

Learning:- Learning : Mechanism by which people improve a skill or knowledge over a period of time. Often based on inductive or abductive reasoning

Consistency reduces mistakes Ensure consistency between applications and across platforms (e.g., Mac vs. Windows vs. Linux) Reduces interference in long-term memory