CMN Model and Fitt's Law

Question 1

what is the idea behind the CMN model

Answer 1

It is an engineering model the derive behavioural characteristics of the users. It models how users react to external input using their basic perceptial, cognition, and motor processors. The model arrives at useful numbers that help to create good interfaces.

Question 2

Name 3 human model processors

Answer 2

1. perceptual processor
2. cognitive processor
3. motor processor

Question 3

CMN is used to model high cognitive models

Answer 3

No, the model is used for simple tasks like hearing things and then reacting by pushing a button

Question 4

what are the inputs and outputs of the perception model?

Answer 4

Input: visual and auditory stimulus
output: working memory( visual image store and auditory image store)

Question 5

what is perception time?

which law is associated with it?

Answer 5

100ms

Bloch’s law

Question 6

what does Bloch’s law say?

Answer 6

It is associated with the perception processor. It says that Reaction = Intensity*exposure time.
It tells that humans have a constant reaction when the exposure time is less than 100ms

Question 7

If there are n events happening in then 100ms, how many events are seen by humans according to Bloch’s law?

Answer 7

1

Question 8

what is the effect of contrast in the perception processor?

Answer 8

High contrast helps in distinguishing between events. Less contrast like in movies is easy to show flowing events.

Question 9

What is an application of perception processor?

Answer 9

100ms is the time to create meaningful interactions response i.e feedbacks. If feedback is given after 100ms it breaks down the constant response cycle.

Question 10

are chunks user-dependent? and it is task-dependent?

Answer 10

Yes, chunks are user-dependent. It depends on concepts a user has in his/her long term memory like 2407 can be remembered as a birthday date by someone. yes, it is task-dependent too.

Question 11

how many chunks are usually remembered by people in their working memory?

Answer 11

4 +- 1

Question 12

what is the cognitive processor processing time?

Answer 12

70ms

Question 13

what is the capacity of long-term memory? how is it able to make associations?

Answer 13

infinite capacity and half-life. It uses Semantic encoding to make associations. like with apple we make associations with shape, color, size, etc. It has fast read and slow writing in LTM

Question 14

What is the application of Cognitive processor?

Answer 14

The dropdown menu should have 4-5 items so that they are easy to parse and remember after using it for a while.

Question 15

what is the average time between each reversal in the motor processor?

Answer 15

70ms

Question 16

what is an open-loop?

Answer 16

Open-loop involves only the motor processor. like drawing random lines on a sheet. so open loop is 70ms long

Question 17

what is the closed-loop?

Answer 17

In closed-loop, we are using all human processors like perception, cognition, and motor. Tasks like correcting the lines between a shape. So takes 1(00+70+70)ms also known as reaction time.

Question 18

what are different types of indexes in fitts law?

Answer 18

There are 2 types of indexes:

index of movement(constant: depends on the device) and index of difficulty(in bits : log(2D/W))

Question 19

what are other parts of CMN model other than processors

Answer 19

short-term memory aka working memory that has visual and auditory image storage.
long term memory

Question 20

Does fitt’s law show a linear relationship?

Answer 20

Not a linear relationship but a logarithmic relationship. given by Doubling the distance adds roughly a constant to execution time like in tapping task

Question 21

what is Shannon’s formula?

how are D and W taken?

Answer 21

a + b*log2(D/W + 1)
D = starting point till midpoint of button
W = in the direction of movement