Users. Perception and Cognition

Transcription

1 Users Perception and Cognition This lecture relies on Designing with the Mind in Mind by Jeff Johnson, The Humane Interface by Jef Raskin, and other sources. 1

2 Ergonomics and Human Factors Designing devices that fit human abilities: physical and cognitive. 2

3 Cognitive Engineering, Cognetics The study of how people mentally work vs. dominant branch of ergonomics which studies how people physically work We must master an ergonomics of the mind if we want to design interfaces that are likely to work well. (Raskin, p. 10) well-known computer interfaces are designed as though their designers expect us to have cognitive abilities that experiment shows we do not possess. (Raskin, p. 10) 3

4 Cognition Faculty for processing information and applying prior knowledge using mental processes like: attention memory learning reasoning Memory Perceptual Processor Cognitive Processor Motor Processor Card, Moran, and Newell s Model Human Processor 4

5 HCI Guidelines The study of cognetics has resulted in many sets of HCI guidelines. They are all substantially the same Why? Unlike fashion design, they are not based on the designer s tastes and whims. They are all based on human psychology: how people perceive, learn, reason, remember, and convert intentions into action. 5

6 Memory 6

7 Short vs. Long-Term Memory Short-term Memory: situations in which information is retained for very short intervals (ε several seconds) Long-term Memory: information is retained over longer periods (minutes, hours, days, years, a lifetime) A tempting view: Perceptions Short-Term Memory Long-Term Memory Input RAM Disk 7

8 Long-Term Memory = Activated Neurons Perceptions enter via visual, auditory, olfactory, gustatory, or tactile sensory systems Activate neurons in areas of the brain are dedicated to each sense Detect low-level features: dark-light edge, diagonal line, highpitched tone, sour taste, red colour, etc. Triggers activation of neurons in other areas of the brain that are not specific to the sensory system. Combine lower-level features into higher-level features: animal, Uncle Kevin, minor key, threat, etc. The set of triggered neurons depends on the features of the input and the context. The more similar two perceptual stimuli are (features and context), the more overlap there is in the sets of neurons that fire 8

9 Long-Term Memory = Activated Neurons Memory formation: long-lasting and perhaps permanent changes to the neurons involved in a neural activity pattern which make it easier to reactivate in the future. Remembering: reactivating the same pattern of neural activity that occurred when the memory was formed. Somehow the brain distinguishes new activations from reactivations. Recognition: New perceptions that trigger an existing pattern. Recall: Triggering an existing pattern without the perception. Strength of a memory depends on How often it s reactivated Strength of the original perceptions Sleep 9

10 Short-Term Memory Not simply neural activations that don t last long. Short-term memory is a combination of perception and attention. Perceptions make available a collection of neural activations Attention selects just several of the many activations that are currently available. Short-term memory is the currently activated neural patterns of which we are aware. 10

11 Characteristics of Short-Term Memory Low capacity Used to say 7 items plus or minus 2 (George Miller, 1956) Most current researchers say this is too high Depends on similarity of items Capacity perhaps best measured in item-features rather than items Volatility Turning attention to a different neural pattern turns it away from some of what it had been focusing on Information can be easily lost from short-term memory if not rehearsed to constantly bring it back into attention 11

12 Implications for User Interfaces User interfaces should help people remember information from one moment to the next. Examples: Modes: Allows UIs to have more functions than controls But people make mode errors do the wrong thing because they forget which mode they re in. Avoid modes or make it obvious which mode is engaged Search results: keep the search terms on screen to help evaluate search results Instructions: keep a sequence of instructions visible while being followed 12

13 Characteristics of Long-Term Memory Error-prone: Think of it as heavily compressed information Some features not recorded Weighted by emotions Retroactively alterable 13

14 Implications for User Interfaces Don t burden long-term memory more than you have to. Example: 14

15 Perception How we take in information 15

16 Perception Our perception of the world is not a true depiction of reality. To a large extent, we perceive what we expect to perceive. Our expectations and therefore our perceptions are biased by: the past: our experience the present: the current context the future: our goals 16

17 Perception Biased by Experience Imagine you own a large insurance company. You are meeting with a real estate developer to discuss plans for a new campus of company buildings. The campus consists of a row of five buildings, some of which include courtyards providing light for the cafeteria and fitness centre. The developer shows you an initial plan: 17

18 Perception Biased by Experience Now imagine that instead of a real estate manager you re meeting with the marketing manager about a billboard ad. The advertising manager shows you a suggestion that shows a single, value-laden word to be placed on the billboards: 18

19 Perception Biased by Experience 19

20 Perception Biased by Current Context The same phrase is perceived differently depending on the list in which it appears: Fold napkins. Polish silverware. Wash dishes. French napkins. Polish silverware. German dishes. The pattern of neural activity that corresponds to recognizing a letter, a word, a face, or any object includes input from neural activity stimulated by the context. This context includes other nearby perceived objects and events, and even reactivated memories of previously perceived objects and events. (Designing with the Mind in Mind, p. 5) 20

21 Perception Biased by Goals In the following toolbox, is there a pair of scissors? Was there a wrench? 21

22 Perception Biased by Goals This is a fairly famous video. If you ve already seen it, please don t blow it for those who haven t. 22

23 Perception Biased by Goals There are two ways in which our current goals bias our perception: Influencing where we look Sensitizing our perceptual system to certain features 23

24 Cognition How we process information 24

25 Two States of Cognitive Processes Cognitive unconscious: processes of which you are not aware at the time they occur. The resources they make available to us are HUGE. Cognitive conscious: processes focused on the relatively few things that you are aware of at the time they occur. The resources they make available to us are tiny (but powerful). (examples) movement from unconscious to conscious from conscious to unconscious Memory cognitive conscious Perceptual Processor cognitive unconscious Cognitive Processor Motor Processor 25

26 Cognetics Understanding that we possess these two distinct sets of limited mental abilities and understanding how they work in relationship to human-machine interfaces is as essential to designing interfaces as is knowing the size and the strength of the human hand when we are designing a keyboard. -- Jef Raskin, THI, p

27 Comparing Cognitive States Property Conscious Unconscious Engaged by Novelty, emergencies, danger Repetition, expected events, safety Used in New circumstances Routine situations Can handle Decisions Non-branching tasks Accepts Logical propositions Logic or inconsistencies Operates Sequentially Simultaneously Controls Volition (your will ) Habits Capacity Tiny Huge Persists for Tenths of seconds Decades 27

28 Locus of Attention def: The feature, object, or idea about which you are intently and actively thinking (in cognitive conscious). Related to focus but... Cannot completely control where our locus will be We can have at most one locus of attention Maybe none More than one locus is actually multi-tasking, not multiprocessing why is this not optimal? Multi-processing can be achieved by combining one locus and one or more automatic activities... Driving and talking, 28

29 Seeing Doesn t Mean We See A single locus of attention filters out many perceptions Tuning out sounds and smells... Implications: some aspects of a UI may be tuned out as well Perceptions persist briefly and then decay quickly Many perceptions do not automatically become memories Implications: 29

30 Seeing Doesn t Mean We See: Change Blindness def: a change in a visual stimulus is unnoticed by observer 30

31 Context Switches There is a significant cost to switching from one locus of attention to another Context switch: about 10 seconds If the same context switch is performed repeatedly... Implications: Protect users (youself!) from context switches Research in interruptability Exploit single locus/context switches Magician Canon Cat/Some Apps (next slide) New message from Feridun 31

32 Canon Cat 32

33 Absorption You can be more or less absorbed in your locus of attention More absorbed: more difficult to transition to another locus requires greater stimulus to effect such a change Examples: Absorption is essential to productivity Implications for UI: 33

34 Absorption s Negative Consequences Eastern Air Lines Flight 401 story Proportional to stress: As stress increases, people concentrate more and more on but a few features of their environment, paying less and less attention to others... You become less likely to see hints, help messages, or other user aids as you become increasingly agitated about the problem. (Raskin, p. 27) Implications for UI: 34

35 Automatic Actions def: any activity done without conscious thought (routines, habits, skills) in cognitive unconscious Performing a task repeatedly makes it easier Eventually, don t need to give it conscious thought Conscious thought may impede the action Automatic tasks enable simultaneous actions If we are doing more than one activity at a time, all but at most one of them are automatic Automatic actions are essential to higher life forms 35

36 Learning and Controlling Automatic Actions Humans cannot avoid developing automatic responses Practice makes perfect vs. Practice makes permanent Sequences of actions become clumped into a single action Cannot interrupt a sequence of less than 1-2 sec. Long sequences can only be interrupted with conscious thought Unlearning automatic actions 36

37 Good Automatic Action Implications Persistent use of any interface will develop automatic actions that are difficult to unlearn Can be good (e.g. consistency, similarity) 37

38 Bad Automatic Action Implications Can be bad (e.g. dangerous automatic actions) Example: File deletion confirmations Any confirmation step that elicits a fixed response soon becomes useless Alternatives? The action you have requested cannot be undone. It will cause permanent loss of the file. If you are sure you wish to delete the file forever, type backward the tenth word in this box. 38

39 Summary Introduction to perception and how it is biased Introduction to human cognition capabilities cognetics cognitive conscious vs. cognitive unconscious locus of attention automatic actions Implication of cognition for design 39