Perception

Question 1

some facts

Answer 1

• more sharp in the middle of the focus
• objects nearer than 25 cm are difficult to focus
• constant near-focusing leads to fatigue
• blind spot about 15-20° from the optical axis in your eye - objects there are not seen directly but “recomputed”
• maximum sampling frequency for images of about 22 img/sec
• Humas are very sensitive to movement outside of about 30° of the main focus - but are able to ignore it (tunnel effect)

Question 2

focus areas

Answer 2

Foveal area: 1-2°
Para-foveal area: 2-5°
Peripheral area: 6-220°

Question 3

Reading Distance

Answer 3

• handy, tablet: 40cm
• watch: 50cm
• computer monitor: 55-60 cm

Question 4

Presbyopia

Answer 4

Altersweitsichtigkeit

happens to everybody and is unavoidable

avoid near point reading in general!

Question 5

visual perception

Answer 5

is the process of extracting meaning from sensory information. It is concerned with recognition and understanding.

Question 6

Vision

Answer 6

Vision is an easier process (compared to visual perception) concerned with detecting color, shapes or edges of objects. Vision does not necessarily require an understanding of the world surrounding us.

Question 7

Gestalt Laws

Answer 7

The Gestaltists, a group of psychologists, identified a number of properties that can be regarded as innate to all humans. Thus, their findings are called Gestalt Laws.

Gestalt Laws are methods that the brain uses to simplify recognition by ordering them

• proximity
• continuity / common fate
• closure
• part-whole relationships
• similarity
• symmetry

Question 8

Gestalt - proximity

Answer 8

Objects that are close i space ore time tend to be perceived together

can be used e.g. for UI arrangement of buttons or information

Question 9

Gestalt - common fate

Answer 9

Objects that “move” together are seen as related

Question 10

Gestalt - Prägnanz, law of good gestalt

Answer 10

unknown figures are automatically separated into known simple forms

Question 11

Gestalt - closure

Answer 11

We tend to see things as complete objects even though there may be gaps in the shape of the objects

closed figures are perceived more easily than incomplete or open figures

Question 12

Gestalt - continuity

Answer 12

We tend to perceive sooth, continuous patterns instead of disjoint, interrupted patterns

Question 13

Gestalt - similarity

Answer 13

Similar figures tend to be grouped together

Question 14

Gestalt - the area principle

Answer 14

Objects with small area tend to be seen as the figure, not the ground
(the smallness principle)

Question 15

Gestalt - Surroundedness Principle

Answer 15

An area that is surrounded will be seen as the figure and the area that surrounds it will be seen as the ground

Question 16

Stimulus Intensity

Answer 16

We respond first to the intensity of a stimulus and only then do we begin to process its meaning

Question 17

Proportion

Answer 17

Proportion can be used to represent logical hierarchies (Überschriftgrößen)

seen as aesthetic:

• golden ration
• fibonnaci …

Question 18

Screen complexity

Answer 18

measure of complexity. can be used to calculate the relative complexity, and therefore the difficulty, of the design

To measure the complexity for a particular screen:

1. place rectangle around every screen element
2. count the number of elements and the number of columns (vertical alignment points)
3. count the number of elements and the number of row (horizontal alignment points)

Question 19

Complexity vs usability

Answer 19

both overly simple and overly complex screens are low in usability

three components:

• effectiveness
• learnability
• attitude

Question 20

Depth Perception

Answer 20

The arrangement of our visual sensors (eyes) allows us to perceive our world three-dimensionally

• primary depth cues: relevant e.g. to immersive virtual reality systems
• secondary depth cues: more relevant e.g. to non-immersive applications such as games

Question 21

Primary Depth Cues

Answer 21

retinal disparity:
* as our eyes are approximately 7cm apart, each retina receives a slightly different image of the world. This is processed by the brain and interpreted as distance information

stereopsis:
* Stereopsis is the process by which the different images of the world received by each eye are combined to produce a single three-dimensional experience

accommodation:
* this is a muscular process by which we change the shape of the lens in our eyes in order to create a sharply focused image. The information from the muscles is unconsciously used for depth information.

convergence:
Over distance of 2-7 meters we move our eyes more and more inwards to focus on an object at these distances. This process is used to provide additional depth information.

Question 22

Secondary Depth Cues

Answer 22

secondary depth cues are the basis for depth perception on two-dimentional displays.

Cues:

• light and shade
• linear perspective: e.g. shadow on an arrow
• height in the horizontal plan
• motion parallax: e.g. when riding on a train and looking out of the window, near objects flash by quickly, objects further way slower
• overlap: e.g. overlapping windows in a GUI
• relative size: see sun + cloud
• texture gradient: textured surfaces appear closer

Question 23

colors - problem with displays

Answer 23

information displayed with additive active light might not be as natural as reflected light

• humans are not used to looking “into” the light
• natural perception is reflected light

additive coloured information presentation should be embedded into an environment that has equal brightness to avoid fatigue

Question 24

color - visual limitations

Answer 24

• blue is on the edge of the spectrum. Avoid using it for small and tiny elements
• the ability to distinguish color is directly related to he size of an object
• shapes are identified by their edges. Edges are faster identified by lins than by colours
• better colour perception in the middle of the focus
• about 8% of men (0.4% of women) have deficiencies to perceive colors correctly. Most deficiency is detection of green

Question 25

Colours may cause emotional response

Answer 25

emotional response varies from culture to culture

people from different age and sex have different preferences (e.g. children prefer colourful objects)

industries, professional communities, corporate have their own colour connotations

Question 26

Color coding

Answer 26

can improve recall, search-and-locate tasks, decision judgements : overall performance

does not replace a good structure!

differences to distinguish color variations vary between colors, individuals and cultures

targets may use highly divers colors from those of their surroundings

Question 27

optimal colors

Answer 27

avoid any incompatible color combination

background to foreground contrast is also important

use max 4 colors on screen with max 4 variants each

Question 28

sound

Answer 28

loudness

• expressed in decibel (dB)
• dB is logarithmic scale (40dB is 10 times louder than 30dB)
• whisper: 15dB
• normal conversation: 60dB
• car horn: 110 dB
• rock concert: 120+ dB

Frequency range of hearing: 20Hertz - 20kHz

Question 29

4 stages of auditory perception

Answer 29

Transduction
* translation of sound vibrations into neural impulses

Auditory grouping

1. segregation into separate streams
2. integration of sound in coherent streams

Scene Analysis

Interpretation

Question 30

Audio User Interfaces

Answer 30

Vision and Hearing go together

Audio can tell your eyes where to look

Audio can perceive faster than visual cues

Audio is transitory! Vision is often not