Human Computer Interaction: The Human

The Human

• Information is sent and received through visual, auditory, haptic, and movement channels.
• Information is stored in sensory, short-term, and long-term memory.
• Information is processed and applied.
• Emotion influences human capabilities.
• Each person is different.

Input-Output Channels

Vision

• Vision involves two stages: physical reception of stimulus and processing/interpretation of the stimulus.
• A stimulus is something that causes a reaction, especially interest, excitement, or energy.

The Eye - Physical Reception

• The eye's physical reception is the mechanism for receiving light and transforming it into electrical energy.
• Light reflects from objects to make vision possible.
• Images are focused upside-down on the retina.
• The retina contains rods for low light vision and cones for color vision.
• Ganglion cells detect pattern and movement.

Interpreting the Signal

Size and Depth

• Visual angle indicates how much of a view an object occupies and is related to size and distance from the eye.
• Visual acuity is the ability to perceive detail, which is limited.
• Familiar objects are perceived as a constant size, despite changes in visual angle when far away.
• Overlapping cues help with the perception of size and depth.

Brightness

• Brightness involves a subjective reaction to levels of light.
• Brightness is affected by luminance of an object.
• Brightness is measured by just a noticeable difference.
• Visual acuity increases with luminance, as does flicker.

Color

• Color is comprised of hue, intensity, and saturation.

• Cones are sensitive to color wavelengths.

• Blue acuity is the lowest.

• 8% of males and 1% of females are color blind.

• The visual system compensates for movement and changes in luminance.

• Context is used to resolve ambiguity.

• Optical illusions occur due to overcompensation.

Optical Illusions

• Optical illusions are illusions caused by the visual system where a visual percept appears to differ from reality.
• Kinds of visual illusions include ambiguities, distortions, paradoxes, and fictions.

Ambiguities

• Ambiguities involve hidden objects that can be revealed by looking at the images from a specific point of view.

Distortions

• Distortions lead to the perception of size, shape, color, and orientation being severely distorted.

Paradox

• Paradoxes depict objects which initially seem normal but, in reality, cannot exist.

Fictions

• Fictions are the perception of objects that are genuinely not there for all but a single observer; these are more properly called hallucinations.

Reading

• Reading involves several stages: visual pattern perceived, decoded using internal representation of language, and interpreted using knowledge of syntax, semantics, and pragmatics.

• Reading involves saccades and fixations.

• Perception occurs during fixations.

• Word shape is important to recognition.

• Negative contrast improves reading from a computer screen.

• Syntax refers to the arrangement of words and phrases to create well-formed sentences in a language.

• Semantics is the branch of linguistics and logic concerned with meaning.

• Pragmatics refers to the branch of linguistics dealing with language in use and the contexts in which it is used.

Hearing

• Hearing provides information about the environment including distances, directions, and objects.
• Physical apparatus includes the outer ear, the middle ear, and the inner ear.
• The outer ear protects the inner ear and amplifies sound.
• The middle ear transmits sound waves as vibrations to the inner ear.
• The inner ear transforms chemical transmitters, which are released and cause impulses in the auditory nerve.

Touch

• Touch provides important feedback about the environment.
• Touch may be a key sense for someone who is visually impaired.
• Stimuli is received via receptors in the skin.
  • Thermoreceptors detect heat and cold.
  • Nociceptors detect pain.
  • Mechanoreceptors detect pressure.
• Some areas are more sensitive than others, such as the fingers.
• Kinesthesis is the awareness of body position that affects comfort and performance.

Movement

• The time taken to respond to a stimulus equals reaction time plus movement time.
• Movement time is dependent on age, fitness, etc.
• Reaction time is dependent on the stimulus type.
  • Response to Visual stimulus = ~200ms
  • Response to Auditory stimulus = ~150ms
  • Response to Pain ~ 700ms
• Increasing reaction time decreases accuracy in the unskilled operator but not in the skilled operator.

The Human Memory

• There are three types of memory function: sensory memory, short-term memory, and long-term memory.
• The sensory memory is related to attention.
• The short term memory is related to rehearsal
• The long term memory is related to the sensory and short term memory

Sensory Memory

• Sensory memory buffers stimuli received through senses.
  • Iconic memory is related to visual stimuli.
  • Echoic memory is related to aural stimuli.
  • Haptic memory is related to tactile stimuli.
  • Gustatory memory is related to taste.
  • Olfactory memory is related to smell.
• "Sparkler" trail and stereo sound are examples of sensory memories.
• The sensory memory is continuously overwritten.

Short-Term Memory (STM)

• STM is also called the working memory.
• STM acts as a scratch-pad for temporary recall.
  • STM allows rapid access at ~70ms.
  • STM allows rapid decay at ~200ms.
  • STM has a limited capacity of 7±2 chunks.

Long-Term Memory (LTM)

• Episodic memory represents the memory of experiences and specific events in time in a serial form. This memory allows reconstruction of actual events that took place at any given point in lives.

• It is the memory of autobiographical events including times, places, associated emotions, and other contextual knowledge that can be explicitly stated.

• Individuals tend to see themselves as actors in these events, where the emotional charge and the entire context surrounding an event is part of the memory, not just the bare facts.

• Semantic memory is a structured record of facts, meanings, concepts, and knowledge about the external world that has been acquired.

• It refers to general factual knowledge that is shared with others and is independent of personal experience and of the spatial/temporal context in which it was acquired.

• Includes such things as types of food, capital cities, social customs, functions of objects, vocabulary, and understanding of mathematics.

• Semantic memory is often abstract and relational and is associated with the meaning of verbal symbols.

LTM – Storage of Information

• Rehearsal moves information from STM to LTM.
• The amount retained is proportional to rehearsal time.
• Distribution of practice effect is optimized by spreading learning over time.
• Information is easier to remember when there is structure, meaning and familiarity.

LTM – Forgetting

• With decay, information is lost gradually but very slowly.
• Interference includes new information replacing old, which is retroactive interference, and old interfering with new, which is proactive interference.
• It may not be possible to forget all memories. Memory is selective, and can be affected by emotion. It is possible to subconsciously choose to forget.

LTM – Retrieval

• During recall, information reproduced from memory can be assisted by cues such as categories and imagery.
• Recognition occurs when information gives knowledge that it has been seen before.
• Also, recognition is less complex than recall since information is the cue.

Thinking: Reasoning & Problem Solving

Reasoning

• Reasoning is the process by which existing knowledge is used to draw conclusions or to infer something new.
• Types of reasoning are Inductive, Deductive, and Abductive.

Inductive Reasoning

• Induction is a method of drawing conclusions by going from the specific to the general.
• Generalization is drawn from cases seen to cases unseen.

Deductive Reasoning

• Deduction is a logical approach where one progresses from general ideas to specific conclusions.
• One can derive a logically necessary conclusion from given premises.

Abductive Reasoning

• Abductive Reasoning involves reasoning from event to cause
• Abductive Reasoing is unreliable as it can lead to false expalanations

Problem Solving

• Problem solving is the process of finding a solution to an unfamiliar task using existing knowledge.

• Several theories exist.

• Gestalt theory states that problem solving is both productive and reproductive.

• Productive involves insight and restructuring of the problem.

• Reproductive draws on previous experience.

• "Functional Fixedness" is a gestalt term referring to when learning or past experience impedes problem solving.

• Problem space theory states that problem space comprises problem states.

• Problem solving involves generating states using legal operators.

• Heuristics may be employed to select operators, like with means-ends analysis.

• Problem solving operates within the human information processing system, and is subject to STM limits.

• Problem solving is largely applied to problem solving in well-defined areas.

• Analogy involves analogical mapping to solve a novel problem in a new domain using knowledge of a similar problem from a similar domain.

• Skill acquisition is a skilled activity characterized by chunking.

• Information is chunked to optimize short-term memory.

• There is conceptual rather than superficial grouping of problems.

• Information is structured more effectively.

Errors and Mental Models

• There are two types of error: slips and mistakes.

SLIPS

• Slips involve the right intention, but failure to do it right.
• Causes are poor physical skills and inattention.
• A change to an aspect of skilled behavior can cause a slip.

MISTAKES

• Mistakes involve the wrong intention.
• Causes are incorrect understanding.
• Humans create mental models to explain behavior.
• If a mental model is wrong (different from actual system), errors can occur.

Emotion

• James-Lange theory says emotion is the interpretation of a physiological response to a stimuli.

• Cannon theory says emotion is a psychological response to a stimuli.

• Schacter-Singer theory says emotion is the result of evaluation of physiological responses given the situation.

• Emotion clearly involves both cognitive and physical responses to stimuli.

• The biological response to physical stimuli is called affect.

• Affect influences how we respond to situations where positive affect leads to creative problem solving and negative affect leads to narrow thinking.

• Negative affect can make it harder to do even easy tasks, while positive affect can make it easier to do difficult tasks.

• Stress during interface design will increase the difficulty of problem solving.

• Relaxed users viewing the interface will be more forgiving of shortcomings in design.

• Aesthetically pleasing and rewarding interfaces will increase positive affect.

Individual Differences

• Long-term individual differences include sex, physical, and intellectual abilities.
• Short-term differences include the effect of stress or fatigue.
• Changing differences include age.
• It is important to ask whether a design decision excludes a section of the user population.