1. CSCD 487/587 Human Computer Interface Winter 2013 Lecture 8 Human Movement and Memory

2. Overview Few more thoughts on humans and their abilities How do movements relate to interface design? How much information can we deal with? How complex should the information be on a screen? Look at movements, and memory

3. Human Memory

4. Human Memory Basic Questions How does information get into memory? How is information maintained in memory? How is information pulled back out of memory? Three processes – Encoding, Storage and Retrieval

5. Figure 7.2 Three key processes in memory

6. Memory Encoding Encoding is crucial first step to creating a new memory It allows perceived item of interest to be converted into a construct that can be stored within brain, Recalled later from short-term or long- term memory.

7. Memory Encoding Encoding is a biological event beginning with perception through senses Process of laying down a memory begins with attention Memorable event causes neurons to fire more frequently, making experience more intense and increasing likelihood that event is encoded as memory

8. Memory Encoding Perceived sensations are decoded in various sensory areas of cortex, and then combined in brain’s Hippocampus into one single experience Hippocampus is then responsible for analyzing these inputs and deciding if they will be committed to long-term memory It acts as kind of sorting center where new sensations are compared and associated with previously recorded ones Various threads of information are then stored in various different parts of the brain,

9. Figure 7.23 The anatomy of memory

10. Storage: Maintaining Information in Memory Information storage in computers is similar Information storage in human memory Subdivide memory into 3 different stores Sensory, I conic - visual stimuli Echoic - aural stimuli Haptic - touch stimuli Short-term, Long-term

11. Figure 7.7 The Atkinson and Schiffrin model of memory storage

12. Sensory Memory Shortest term memory Retain impressions after original stimulii ended Ultra short memory decays quickly 1/5 to ½ second Is the first step to storing in short term memory Information is passed to short term memory via attention Placing attention on it filters stimuli that is of interest

13. Short Term Memory Next in line from sensory memory Scratch pad for temporal recall Brain's post-it notes, holds small amount of information 7 + or – 2 items Recall for short period of time, 10 – 15 secs Example: To understand an entire sentence when you read it, hold beginning of sentence in short term memory Next step towards long-term memory One way to transfer to long-term storage Working memory is short term memory

14. Short Term Memory If memory is to be stored in long-term memory some type of transfer takes place in few seconds Rehearsal – the process of repetitively verbalizing or thinking about the information This is where chunking takes place to help with memory recall:

15. Long Term Memory Memories come to Long-term storage through short term storage Process of consolidation by rehearsal and meaningful association Encodes information semantically Process involves physiological changes to brain – neural networks are created With repeated use, efficiency of neural networks increases Storage occurs throughout brain Slow access - 1/10 second Slow decay, if any Huge or unlimited capacity

16. Long-term Memory Semantic memory structure Provides access to information Represents relationships between bits of information Supports inference Model: Semantic network Inheritance - child nodes inherit properties of parent nodes Relationships between information - explicit Supports inference through inheritance

17. works sheep has four legs barks ANIMAL is aSHEEPDOG breathes is a DOG moves has tail is a is asize: medium COLLIE color: [brown/white, black/white, merle] HOUND instance instance tracks is aLASSIE SHADOW film character size: small BEAGLEcolor: brown/white book charactercolor: brown/white color: [brown, black/white] instance SNOOPY cartoon/book character friend of CHARLIE BROWN Semantic network model of LTM

18. Other Models of L ong Term Memory Frames: Information organized in data structure Slots in structure are instantiated with particular values for a given instance of data. DOG Fixed legs: 4 Default diet: carnivorous sound: bark Variable size: color COLLIE Fixed breed of: DOG type: sheepdog Default size: 65 cm Variable color

19. Script for a visit to the vet Entry conditions: dog ill Roles: vet examines vet open diagnoses owner has money treats owner brings dog in pays Result: dog better takes dog out owner poorer vet richer Scenes: arriving at reception waiting in room examination Props: examination table paying medicine instruments Tracks: dog needs medicine dog needs operation Other Models of long-term Memory Scripts: Model of stereotypical information required to interpret situation or language.

20. Accessing Memories Retention – the proportion of material retained Recall Recall is a way that you obtain information from your memory without having a cue to prompt the response. You have to essentially draft the information without any assistance. Recognition Recognition is how you respond to a sensory cue. You look at something and your mind looks to see if what you are seeing in front of you matches anything that has been stored. If you notice a match, you are recognizing the information. Example: Taking a test, multiple choice is recognition, short answer is recall

21. Figure 7.16 Ebbinghaus’ forgetting curve for nonsense syllables

22. Figure 7.17 Recognition versus recall in the measurement of retention

23. Long Term Memory How do we forget information? When neural networks become weak from lack of use When we impose new neural networks on top of old networks causing interference with old network Memory is selective and affected by emotion - can “choose” to forget Also varies by sex, physical and intellectual abilities Changes with age

24. Figure 7.19 Retroactive and proactive interference

25. Memory Implications for Design

26. 26 Recognition over Recall As we said... Recall Info reproduced from memory, no cues Recognition Presentation of info provides knowledge that info has been seen before Easier because of cues to retrieval We want to design UI's that rely on recognition!

27. Short term Memory Limits Misconception that limited short-term memory should be limited to 7 items!!! It's fine to have longer menus (if needed) – Users don't have to memorize the full list of menu items The entire idea of a menu is to rely on recognition rather than recall But if you make a menu too short, the choices become overly abstract and obscure.

28. Specifically for Web Design Response times must be fast enough that users don't forget what they're in the middle of doing while waiting for the next page to load Change color of visited links so that users don't have to remember where they've already clicked Also counts as providing feedback to users

29. Specifically for Web Design Offer help and user assistance features in the context where users need them So they don't have to travel to a separate help section and memorize steps before returning to the problem at hand This goes for other non-web interfaces too

30. Individual Differences Huge individual differences in user performance Top 25% of users are 2.4 times better than the bottom 25% Only about 4% of the population has enough brainpower to perform complex cognitive tasks such as making high-level inferences using specialized background knowledge If you forget these limits, users will find your site very frustrating

31. Measuring Motor Movement

32. Movement – Fitt’s Law Fitts' Law, 1954 –Fundamental law of human sensory-motor system –Practical application in interface design –Describes the time taken to hit a screen target –Time, Mt, to move hand to a target of size, S, at distance, D, away Mt = a + b log 2 (D/S + 1) where:a and b are empirically determined constants Mt is movement time D is Distance S is Size of target – “index of difficulty”: log 2 (D/S + 1) Same performance at greater distance with greater size  targets as large as possible, distances as small as possible

33. Fitt’s Law Which is the easiest to hit? HIT ME 4 cm 1 cm 5 cm T = 100 log2(4/1 + 0.5) = 9 ms T = 100 log2(4/5 + 0.5) = 2.6 ms

34. 34 Fitts’ Law Example Which is the easiest to hit? Today Sunday Monday Tuesday Wednesday Thursday Friday Saturday Pop-up Linear Menu Pop-up Pie Menu

35. Fitt’s Law Implications Hierarchical menus are hard to hit –Especially when it takes two actions …

36. Take a Quiz Try out Fitt's Law Concepts from AskTog http://www.asktog.com/columns/022Designe dToGiveFitts.html

37. Summary Human memory models important – Otherwise, we as designers will underestimate or overestimate our users – Users will get frustrated if their mental capacities are not accounted for in products they use !!!

38. References Short-Term Memory and Web Usability by J. Nielsen http://www.nngroup.com/articles/short-term-memory-and- web-usability/ Human Memory http://www.human-memory.net/brain_parts.html

39. The End Reading … on to Chapter 4