HCI: The Human - Vision

• Text is about the human aspects of Human-Computer Interaction, including vision, hearing, touch, movement, memory, thinking, errors, emotions, and individual differences

Vision

• Involves physical reception of stimuli and its processing/interpretation.

The Eye

• Transforms light into electrical energy.
• Light reflects from objects and forms upside-down images on the retina.
• The retina contains rods for low light vision and cones for color vision.
• Ganglion cells detect patterns and movement.

Interpreting Visual Signals

• Visual angle indicates how much of the visual field an object occupies and relates to size and distance.
• Visual acuity refers to the ability to perceive detail, which is limited.
• Familiar objects are perceived as constant in size, and cues like overlapping aid in perceiving size and depth.
• Brightness is a subjective reaction to light levels, affected by object luminance and measured by the just noticeable difference, acuity increases with luminance.
• Color perception involves hue, intensity, and saturation; cones are sensitive to color wavelengths, with blue acuity being the lowest; 8% of males and 1% of females are color blind.

Visual System Adaptations

• Context aids in resolving ambiguity
• Optical illusions can occur due to overcompensation

Reading

• Reading involves multiple stages: visual pattern perception, decoding using internal language representation, and interpretation using knowledge of syntax, semantics, and pragmatics
• It involves saccades and fixations, with perception occurring during fixations
• Word shape and negative contrast improving reading from computer screens

Hearing

• The auditory system provides information about distances, directions, and object
• The outer ear protects and amplifies sound, the middle ear transmits sound waves, and the inner ear releases chemical transmitters that create auditory nerve impulses
• Sound consists of pitch (frequency), loudness (amplitude), and timbre (quality)

Frequency Range

• Humans can hear frequencies from 20Hz to 15kHz but distinguishing high frequencies is less accurate
• The auditory system can filter out sounds over background noise such as the cocktail party phenomenon

Touch

• touch gives important feedback in the environment
• Especially helpful for visually impaired people
• Receptors in the skin are: thermoreceptors for heat and cold, nociceptors for pain, and mechanoreceptors for pressure
• Sensitivity varies across different areas of the body, for example, fingers are particularly receptive
• Kinethesis relates to awareness of body position and affects comfort/performance.

Movement

• Reaction time plus movement time constitutes the total time to respond to a stimulus
• Movement time depends on factors like age and fitness
• Reaction time differs based on the stimulus type: visual stimuli ~ 200ms, auditory ~ 150 ms, pain ~ 700ms
• Increased reaction time reduces accuracy for unskilled operators, but not for skilled ones.

Fitts' Law

• Fitts' Law explains that time to hit a target is related to the size of the target and distance
• Mt = a + b log2(D/S + 1), where Mt is movement time, D is distance, S is size, and a/b are constants
• Target sizes should be large and distances should be small

Memory

• There are three memory function types: sensory memories, short-term memory, and long-term memory
• Selection of stimuli is based on level of arousal.

Sensory Memory

• Buffers stimuli received through senses
• Iconic memory for visual stimuli, echoic memory for aural stimuli, and haptic memory for tactile stimuli
• Examples include "sparkler" trail and stereo sound
• Continuously overwritten.

Short-Term Memory (STM)

• STM acts as a temporary scratch-pad for recall.
• Access time ~ 70ms and decays rapidly ~ 200ms.
• Limited capacity of 7± 2 chunks.

Long-Term Memory (LTM)

• Acts as a repository for knowledge
• Slow access time ~ 1/10 second, slow decay if any, and huge capacity
• Two LTM types are episodic which is serial memory of events and semantics a structured memory of facts ,concepts, and skills

Semantic Memory

• The memory structure provides access to information
• Represents relationships, and supports inference

LTM Models

• Semantic networks, frames, scripts, and production rules

LTM Storage

• Occurs through rehearsal, with the amount retained proportional to rehearsal
• Optimized by spacing out learning over time
• Information with structure, meaning, and familiarity is easier to remember.

LTM Forgetting

• Information is lost gradually, other information replaces old (retroactive), or old interferes with new information (proactive inhibition)
• Memory may be selective and affected by emotion, leading to subconsciously `choosing' to forget in some cases

LTM Retrieval

• Recall involves reproducing info from memory with cues
• Recognition occurs when provides one previously seen with less complexity

Thinking

• Involves reasoning and problem-solving

Deductive Reasoning

• Derives a logically necessary conclusion from given premises
• The logical conclusion is not always necessarily true
• People use real-world knowledge in deduction.

Inductive Reasoning

• Generalizes from observed cases to unseen ones
• Though unreliable it can only prove false

Abductive Reasoning

• Abductive reasoning infers a cause from an event
• May lead to false explanations

Problem Solving

• Problem solving is finding a solution to unfamiliar using knowledge.
• Gestalt theory includes insight and problem restructuring
• Problem space theory includes heuristics to select operators, operates within STM limits, and is applicable towards puzzles

Analogy and Skill Acquisition

• Analogy relates to novel problems and use new information from previously similar problems
• Skill acquisition includes chunking to optimize STM, conceptual grouping, and info is more effectively structured.

Errors and Mental Models

• Slips occur from right attention but with failed execution: with causes like poor skill or inattention, even a change in skilled behavior can cause it
• Mistakes occur from wrong intention, based on incorrect understanding

Understanding Emotion

• James-Lange: interprets response to stimuli
• Cannon: psychological response
• Schacter-Singer: result of physiological repsonses
• Emotion combines cognitive and physical responses

Affect

• The biological response to physical stimuli
• Positive emotions result in creative problem solving and negative emotions result in narrow thinking
• Negative emotion can make small tasks hard, positive makes hard tasks small

Implications for Interface Design

• Stress will increase difficulty of problem solving
• Relaxed users will be more forgiving
• Aethestically pleasing interfaces will create positive affect

Individual Differences

• Long term differences include sex, physical and intellectual abilities
• Short term is stress and fatigue
• Always consider if any design decision will exclude any users