SWEN303 Lucky Number Slevin OR The Magical Number Seven, Plus Or Minus two: Some Limits On Our Capacity For Processing Information

Rule of Seven Seven is a pretty magical number Miller (1956) showed that human working memory can store about 7 things This has been interpreted in many interesting ways E.g. You can only have 7 things on the screen at one time

Miller’s Experiment? There isn’t one Miller collated a number of other works together

Channel Capacity This considers the number of groups an observer can correctly distinguish There is no time limit Recorded by number of bits to represent the number (log 2 ) Compare input information to output

Pollack Asked users to distinguish tones (1 – 14) Tones from 100 – 8,000 hz in equal log steps  Note that up one octave is double the frequency

Garner Asked users to distinguish loudness (4, 5, 6, 7, 10, and 20 categories) Loudness varied from 15 – 110 dB

Beebe-Center, Rogers, and O'Connell How salty is water? Ranging from 0.3 – 34.7 g NaCl / 100 ml tap water in equal steps Sets of 3,5,9, and 17

Hake and Garner Users had to judge pointer position (5,10,20, or 50 positions) Filled circles are ones where users had to guess entirely, while unfilled circles are where possible options were given 0 100

Wait really? Some people have perfect pitch – but not most If I can do two sequences of 5 pitches in different parts of the scale, can’t I combine those in a sequence of 10? Nope :(

And more! Eriksen and Hake: sizes of squares – 2.2 bits Eriksen: size bit, hue bits, brightness bits Gerald: chest skin sensitivity - 4 intensities, 5 durations, 7 locations Air Force Operational Applications Laboratory: Lots! Overall: Mean bits, standard deviation – 0.6 bits

What about 2D – Klemmer and Frick Position of a dot in a square 4.6 vs 3.25 for a line

Multiple Dimensions Beebe-Center, Rogers, and O’Connell: sweetness & salitiness – 2.3 bits Pollack: pitch & loudness – 3.1 bits Halsey and Chapanis: hue & saturation – 3.6 bits Pollack and Ficks: 6 acoustic variables – 7.2 bits They don’t sum linearly!

Immediate memory Immediate memory has a similar limit You can remember about 7 chunks (things) Unlike absolute judgement, the amount of information is not constant

Recoding We can think of a sequence of binary digits as a sequence of numbers