pattern recognition

Pattern Recognition

Nick LundAttention and Pattern Recognition

Introduction

Pattern recognition has been defined as ‘the ability to abstract and integrate certain elements of a stimulus into an organised scheme for memory storage and retrieval’ (Solso,1998).

Features of pattern recognition

Five principles(Solso,1998):

1.Quickly and accurately.

2.Recognise and classify unfamiliar objects.

3.Accurately recognise shapes and objects from different angles.

Features of pattern recognition

4.Identify patterns and objects even when partly hidden.

5.Recognise patterns quickly,with ease,and with automaticity.

Features of pattern recognition

Template matching theories

Feature analysis

Prototype theories

Top-down and bottom-up processing

An examination of the theories of pattern recognition raises the question of whether pattern recognition involves top-down or bottom-up processing.

Bottom- up process

Template matching theoryGeons (Structural- description theory)Feature theoryPrototype theory

Template matching theory

External stumuli matches internal templateVast numbers of templates are storedTemplates are created by experience– E.x.: visit Russia

Problems:– 1) Only occurs when there’s a one-to-one match

• Payne and Wenger (1998)

A

A

AA

2) Where are all these templates stored?

3) Slow process

Ex.: recognize 1000-1500 letters a minute

4) To recognize new variations of a pattern (Solso, 1998)

Geons (Structural- description theory)

Biederman (1987)

Limited number (24) of simple geometric shapes , or geons for us to analyse patterns.– Ex.: mug v.s. bucket

Geons

Advantage:– Recognize pattern from different angles

Disadvantage:– Can’t explain why we recognize a particular

chair.– Ex.: My face v.s. my friend’s face

Feature theory

Patterns are recognized by analysis of the individual features of the pattern.– Ex.: MANGO

M

A

Four stages of pattern recognition– Image demons: record the image and pass it– Feature demons: analyse the image for specific

feature• Ex.:

Pandemonium model (Selfridge, 1959)

– Cognitive demons: detect the present feature and shout

– Decision demons: pick up the loudest feature

Advantage:

More flexible than template theory– Ex.: A , regardless of size, shape or

orientation– Neisser: M → N H M V → longer RT (more distracter) M → O M Q G → shorter RT

Disadvantage:

1) Fail to account for the effects of context and expectations

– Ex.:2) Two experiments which can’t explain feature

theorya. Fail to detect “t” in “the” (Healy)b. Teacup, eyebrow → cup, eye ; eac, ebr (Inhoff

and Topolski)

3) Eysenck and Keane:– How can we recognize patterns when their

features are hidden from view?4) Relationship between the features

– Ex. : T v.s. L

The biology of feature theory

Hubel and Wiesel (1959)In visual cortex:– Simple cells: particular orientation, specific

location– complex cells: lines or edges, in all visual field– Hypercomplex cells: length and angles,

combination of features

Disadvantage:

1) Some questioned the existence of hypercomlex cells

2) How specialized they need to be?3) Run out of cells

Prototype theoryExternal stimuli matches with internal abstract prototype

– Ex.: R, compare to all other “R”s

Solso(1998): two theoretical models①Central-tendency model:

– The average, mean②Attribute-frequency model:

– Most common combination, mode

Advantage:

1) More “economical” than template theory– Don’t need templates for every shape, size,

orientation

2) Explain the speed of recognition of letters, words and patterns / novel stimuli

Disadvantage:

1) can’t explain the effect of context (Eysenck, 1993)

– old woman v.s. young lady

2) B, R, P have similar prototype

Top-down processing

Word superiority effect Rat-Man demonstration

Rat-Man demonstration

Rat-Man demonstration

Rat-Man demonstration

The effect of context

Pattern Recognition

Theories– Template matching– Feature analysis

– Prototype Central-tendencyAttribute- frequency

Summary

Summary

Top-down processing

Bottom- up processing

Word superiority effect

Rat-Man demonstration

Geons

Pandemonium model

THE END