in order to design something for someone, we need to understand the capabilities and limitations of...

The Human

Cognitive Psychology

In order to design something for someone, we need to understand the capabilities and limitations of that person How humans perceive the world around them How humans store and process information and

solve problems How humans physically manipulate objects

Models of the User

Model Human Processor

Our Model

Cognitive System

PerceptualSystem

MotorSystem

CPU

I/O

Memory

Human I/O Channels

Input via the senses Sight Hearing Touch Taste Smell

Output via motor control Limbs (feet?) Fingers Eyes Head Voice

The Human Eye

Cornea and lens focus light onto the… Retina, which contains Photoreceptors:

rods - brightness cones - color (red, green and blue)

Ganglions, which are nerve cells that... (X-cells) - detect pattern (Y-cells) - detect movement

Fovea - center of vision

Visual Perception

Depth Size constancy - smaller means farther Occlusion - obstructed means farther Texture - finer means farther

Brightness - contrast (and flicker) Color

150 hues 7 million shades

Reading

Saccades - eye scans forward Fixations - eye is still

Perception happens 94% of the time

Regressions - eye looks back (complex) 9pt,12pt equally legible Books faster than computers

Hearing

Auditory canal -> eardrum -> ossicles -> cochlea -> cilia

Sound parameters Pitch - frequency Loudness - amplitude Timbre - waveform of sound

Stereo location of source Cocktail party effect

Touch

Haptic perception Skin receptors

thermoreceptors - heat, cold nociceptors - intense pressure, heat, pain mechanoreceptors - pressure

Two point test - haptic accuity

Movement

Kinesthesis - Do you know where your limbs are? Reaction time vs. accuracy Fitts’ law:

Movement time = a + b log (distance/size + 1)

Memory

Three kinds of memory sensory short term long term

Sensorymemory

AttentionWorkingmemory

RehearsalLong-termmemory

Sensory Memory

Human Cache Memory Iconic memory - visual

Persistence of vision .5 seconds

Echoic memory - aural Haptic memory - touch Arousal - level of interest or need

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Short Term Memory

Human DRAM (Dynamic random-access memory) 70ms access time 200ms refresh time Size: 7 +/- 2 items

digits chunks words

Recency effect - last is best

Fun with Working Memory

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456 295 1413

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Long Term Memory

The Human World-Wide Web Two types

episodic - events, organized temporally semantic - facts, organized associatively

Representations semantic nets frames scripts

SEMANTIC NETWORK

Frames

Extends semantic nets to include structured hierarchical information

University

Fixed: type of school

Default: has colleges

Variable: public/private

Universitas Gunadarma

Fixed: type of University

Default: public

Variable: campus

Scripts

Stereotypical information Entry conditions: need job, have money Result: educated, less money Props: books, schedule, new car Roles: instructor talks, students listen Scenes: classroom, dorm Tracks: internships, apprenticeships

Processes

How does information get from short term memory into long term memory? Total time hypothesis - hit the books Distribution of practice effect - don’t cram Meaning - concrete better than abstract

faith age cold tenet quiet logic idea value past boat tree cat child rug plate gun flame head

Structure, familiarity and concreteness

How We Forget Decay

Logarithmically - forget most early Jost’s Law - if two equally strong memories at a given

time, then the older is more durable. Interference

retroactive interference - old phone number (later learning) proactive inhibition - driving to the old house (previous memories) emotion - good old days, forget the mundane

Information Retrieval

How do we recall details? Categorization Visualization 1 roti

2 sepatu

3 pohon

4 pintu

5 sarang

6 tongkat

7 surga

8 pagar

9 teh

10 ayam

Real Intelligence

How is information processed and manipulated? Animals - receive and store info, but do not

process it as well as humans Computers - receive and store info better then

humans, but do not process it as well as humans

Human Intelligence

Humans use information to Reason & solve problems Even if the info is partially missing or completely

absent!Human thought is

conscious & self-aware capable of imagination

Reasoning

Inferring missing information Deductive - conclusions Inductive - generalizations Abductive - suppositions

Deductive Reasoning

If A then B A. Therefore B not B, therefore not A.

• Telepon berdering pada saat saya mandi Bila saya mandi, maka telepon berdering Bila telepon berdering, saya mandi Bila saya tidak mandi?

Inductive Reasoning

Specific A has property B then all A is B Gajah memiliki belalai Komputer lambat Lelaki memiliki kumis Perempuan memakai anting

Abductive Reasoning

From fact to the action that caused it Mata bengkak Tanah Becek Helai rambut panjang di kemeja

Problem Solving

Using knowledge to find a solution Gestalt theory Problem space theory Analogy

Gestalt Theory

Finding new solutions Reproductive problem solving

Learned behavior, trial and error Behavioralist Fixation

Productive problem solving Invention, innovation, insight

Problem Space Theory

Mapping out a solution step by step Problem states, goal state, current state Legal state transition operators Heuristics, e.g. means-ends analysis Examples

Games: 15 puzzle, chess Tasks: Setting the VCR clock Life (emphasis on “legal”)

Analogy

Applying one solution to a different problem Analogical mapping Purely productive reasoning is hard (10%) Drawing analogies is easier (80%) Existing solution “semantically close” to problem

domain

Skill Acquisition

Solving problems that are not completely new e.g. Chess

Same goal (different goal states) Same transitions Different “skills”

Problem groups novices group problems superficially experts group problems conceptually

ACT Skill Acquisition Model

How is skill acquired?

General rules

Specific rules

Tuned rules

Proceduralization

Generalization

Errors

How do we make mistakes? Slips - change in context of skill Mental models - incorrect interpretation of the

evidence

Design

How do we use what we know about humans to make better user interfaces? Guidelines Models Evaluation