1. “Laws” of Human Performance
ECE 695
Alexander J. Quinn
January 24, 2018

2. Miller’s Law Memory span is limited to 7 ± 2 chunks
“Memory span” is the number of items a person can remember for short periods of time and repeat back correctly
“Chunks” are the mental units we use to remember things.
You saw this previously in the Model Human Processor paper.

3. Miller’s Law ↓

4. (depends on the person)
Miller’s Law ↓
????
(depends on the person)

5. Miller’s Law relates to short-term memory
(Memorizing digits of PI is long-term memory.)
Miller’s Law

6. Short-term memory (not long-term) Chunks may be person-specific
Miller’s Law
Short-term memory (not long-term)
Chunks may be person-specific
May vary depending on…
kind of chunk
age
person
trial

7. How long does it take to choose among n choices?
Hick’s Law
How long does it take to choose among n choices?
Credit:

8. Hick’s Law dbultiores utiongernh iterephyar hervajoycl ailludietf
liginaterr
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andrefusen
mpustinicu
calorincus
aryondiend
onteredrax
dibloganto
coliterity
oureashall
larithanex
ctaindroar
rashinesgr
lopremites
egookerlin
riveyeator
oryphardic
endesomale
somporthem
rcillouste
fertiveruc
sycedreadl
rflethochn
groafterig
triyanatep
trisopanam
ialtsonett
untibberna
Credit:

9. Hick’s Law kadandicon minianetil nobsonoedy opoilimpad rfressisha
scantontra
Credit:

10. Hick’s Law for making choices
𝑅𝑇=𝑎+𝑏 log⁡(𝑛)
RT is the the reaction time to make a choice
a, b depends on the type of task and is determined experimentally
n is the number of choices

11. Hick’s Law
Credit:

12. Fitts’ Law A W

13. W A
Fitts’ Law
Credit: Paul M Fitts, Journal of Experimental Psychology, Vol 47 No 6, June 1954

15. W A
Fitts’ Law
𝑀𝑇=𝑎+𝑏 log 2 2𝐴 𝑊

16. 𝑀𝑇=𝑎+𝑏∙𝐼𝐷 𝐼𝐷= log 2 2𝐴 𝑊 Fitts’ Law
MT is the average time to point to a task
a, b depend on the input device and are determined experimentally
ID is the index of difficulty for a target
𝐼𝐷= log 2 2𝐴 𝑊

17. 𝐼𝐷= log 2 2𝐴 𝑊 Fitts’ Law ID is the index of difficulty for a target
A = amplitude (distance to move)
W = width, relative to the axis of motion
2 is to ensure that the ID is always positive

18. W A
Fitts’ Law, derivation
In time duration t, you move a fixed proportion (1-r) of the remaining distance
After 1t, the distance remaining is rA.
After 2t, the distance remaining is r2A.
After nt, the distance remaining is rnA.
Solve for n.
𝑟 𝑛 𝐴= 𝑊 2
𝑛= log 𝑟 𝑊 2𝐴
𝑛= 1 log 2 𝑟 log 𝑊 2𝐴
𝑛= 1 log 2 𝑟 − log 𝐴 𝑊
n is the number of time steps needed to complete the full movement.
Credit:

19. See resources page on web site
More…
Power Law of Practice
Forgetting curve
Sensitivity to delay
See resources page on web site