PowerPoint Presentation - Face recognition - Amazon S3

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17 Νοε 2013 (πριν από 3 χρόνια και 11 μήνες)

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60 minutes eyewitness segment (13 min)

The Forensic Artist

∙ A forensic artist is called in when a sketch of a person is
needed to notify the public that he/she is missing, identify a
suspect, or eliminate a suspect.


∙ Usually, the forensic artist goes about his/her job by carefully
listening to an eyewitness or victim’s description of the missing
person, then accurately translating his/her depiction into a
composite drawing.

∙ This sketch is then put on flyers, and given to the police,
television news stations, etc. in order to help with the search.

Picture:
www.ppdonline.org/ ppd_reports.htm

Forensic Artist Levels of qualifications


120 hours of education: 80 hours of composite art
from an approved school and 40 hours in related
courses


A minimum of five years with a bona fide law
enforcement agency



Five successful composite drawings (hits),
including written description of case specifics and
how the drawings were completed



Three letters of recommendation, one from a
supervisor certifying the submitted drawing
samples



A written, practical, and verbal exam including an
"on the spot" composite sketch based on a pre
-
selected photographed "suspect"

In the United States, forensic artists
are also trained in


human anatomy


odontology (study of teeth)


Age progression


Psychology


3D imagery.


Their talents are called upon for
courtroom sketches, "wanted" posters,
drafting crime scenes, medical
drawings for autopsies, and facial
reconstruction from skulls.

Importance of faces:


Central role in human interactions


Contribute to speech perception (McGurk effect)


Communicate a wealth of social information:


Age, gender, personal identity (physical structure)


Mood and emotional state (facial expression)


Interest / attentional focus (direction of gaze)


Faces as visual stimuli:


Faces as a category

highly homogenous (similar)


Share basic component parts in a fixed configuration


(2 eyes over a nose over a mouth inside an ellipse)


Individual faces

highly different


Vary in many dimensions, including head shape, individual features,
relative feature placement, color, texture, etc.


Dynamic and changeable due to movable parts that change shape
and relative position


Example: a smile vs. an angry frown


the same face?













A single face can produce radically different images on our retina when it changes
expression and/or orientation (Farah, 2000).

Demands of face recognition:


Generally same as for object recognition


Recognition in context (object in a clutter of other objects in the scene)


Object invariance (across different viewpoints, sizes / distances, &
illuminations; in motion, etc.)


Specificity (matching visual object to specific semantic description)


But
--

faces require higher specificity!

(exemplar vs. category level)


In most situations, we need to recognize a
specific individual face

(e.g.,
as Joe Smith) rather than the general category (“face”)


Forensic Artist and Missing Children

∙ If a child is missing for a long period of time, or an
unidentified skeleton of a missing child is found, the
forensic artist is called upon to help make a sketch of the
missing child.


∙ In cases like these, when the forensic artist needs to
work from an old photograph or a skull, a facial
reconstruction artist is called to help.

Picture:
www.epm.ornl.gov/viz/apps/f
-
skull.jpg

∙ The facial reconstruction artist uses either a 2D or 3D
technique to construct the face of a missing child from a
skeleton, or an old photo.


Picture: www.headsketch.com

2
-
Dimensional Facial Reconstruction

Picture: www.crimelibrary.com/forensics/art/images/Two
-
dimensional
-
facial
-
reco.jpg

Procedures:

∙ The unidentified skull is placed on a stand, in the
Frankfort Horizontal position.

∙ Tissue markers are placed on the skull.

∙ A ruler is placed beside the skull.

· Photos are taken of the skull’s frontal and profile
views.

∙ The photos are taped side by side, in the Frankfort
Horizontal position, on two separate flat wooden
boards.

∙ Transparent natural vellum sheets are taped down on
top of the photographs.


· Following the skull’s natural contours, and using
tissue markers as guidelines, the forensic artist
creates a sketch of the unidentified person.

∙ Approximate measurements for the mouth, nose, and
eyes are made.

∙ Hair type, and style are determined by other evidence
collected from the crime scene that give clues as to
the kind of life the unidentified person led.

Age Progression


If a child is missing for an extensive period
of time, and only outdated pictures are
available; a forensic artist may use age
progression to help in the identification
process.



Procedure:


-

An outdated picture or sketch of child is
period of time is obtained.



-

Information is gathered on the suspect or
victim, such as: lifestyle, genetics (
for weight
considerations
) and occupations, etc.



-

The artist produces an educated estimation
on how the individual should look.

Picture: www.missingkids.com/assets/images/age.jpg

Picture: www.cnnw.net/~nmclc/Pca24.JPG

Computer Generated Age Progression

Picture: www.ncsd.com/MissingChildren/mort
-
today.JPG

∙ If computer software is used, the artist can use
image enhance to add features such as
eyeglasses, mustaches, beards, hats, different hair
styles, and numerous other items on the photo.


∙ Computer programs such as Photoshop are used
to paint directly on a digitized photograph of the
victim.


Picture:
www.chilhavisto.rai.it/CLV/img/ C/Celentano/grandi/AGING.JPG

Facial Composites

Investigators

work

with

sketch

artists

and

eyewitnesses

to

create

facial

composites
,

or

sketches

of

a

person’s

face
.

Today

many

police

departments

are

using

facial

reconstruction

software

to

help

them

with

this

task
.

The

composite

may

be

used

internally

to

assist

officers

in

identifying

the

suspect

or

used

externally

through

local

media

(radio,

TV,

and

newspaper)

to

solicit

leads

from

citizens
.

FACES



A

software

program

that

offers

many

options

to

help

you

recreate

a

person’s

facial

features
.

The shape of the face

The shape of the jaw

The shape of the eyes

The shape of the nose

The width of the neck

The shape & protrusion of the ears

The presence of facial piercing

The presence of facial hair, its color, & location

The presence of facial markings, such as scars or tattoos

Forehead or other facial lines

The presence of eyeglasses or sunglasses

The length, color, & texture of the person’s hair

You will have a chance to try to create a facial composite. You
will need to pay close attention to the following features:

Find the human face in the display as fast as you can. Ready?



Now find the animal face. Ready?



Forensic Artist


Let’s give it a try….

Study this photo for 30 seconds



Pop
-
out effect for faces! (Herschler & Hochstein, 2005)





demonstrates our expertise in face processing

Perceptual expertise:


Humans are experts at face processing (Diamond & Carey, 1986)


Effects of accumulated lifelong experience & daily practice


Face representations always at least partially activated?


Biological predisposition?


Newborn infants will detect and track a human face more readily than
another visual object (Johnson & Morton, 1991)


Prosopagnosia:


Impairment in face recognition (“face blindness”)


Cannot

recognize familiar faces or own face in the mirror


Can

recognize faces as a category vs. other objects


Can

recognize familiar people by voice and other non
-
facial clues


Vision otherwise OK


Due to brain injury (typically to the right temporal lobe)


Socially crippling


What is it like to be face blind?





People who are ‘tone deaf’ are not deaf to tones.
They can hear tones, they just can't tell them apart.
People who are ‘color blind’ can see things that are in
color. They just can't tell colors apart. Similarly,
I can
see faces. I just can't tell them apart
.”


“If you are face blind, in social settings, or even
when watching TV, people will have come and gone long
before you can identify them. So you never do. By the
time
eight seconds

have passed, people in your
presence who don’t know of your face blindness will be
offended at your failure to recognize them. And long
before you even get your eight seconds, you know you will
be criticized for ‘staring’…”


--

Bill Choisser,
Face Blind!


www.choisser.com/faceblind/


The Capgras delusion:


A form of delusional misidentification due to brain injury


Patients claim that their relatives have been replaced by identical
-
looking
impostors, clones, robots, Martians, etc. (Capgras & Reboul
-
Lachaux, 1923)


Recognize relatives visually but have
a deeper, overwhelming sense

that they
are unfamiliar, strange, not who they claim to be, etc.


Carries a serious risk of violence


Loss of appropriate
emotional response

to visual stimuli?



Emotional recognition is faster than perceptual recognition!




Theories of face recognition:


1) Specialized face module


Functionally and anatomically separate


Processes faces
only


2) Faces processed by the general visual system (no
specialized face module)


Specialized face
-
module hypothesis:


Fusiform Face Area (FFA)
?


Right inferior temporal cortex


Along the ventral / occipitotemporal “what” pathway


Case studies of prosopagnosia


damage typically to FFA


Single
-
cell recordings in monkeys:
face cells
? (Baylis et al., 1985)


fMRI studies of humans: FFA selectively activated by faces
(Kanwisher et al., 1997)


But




Evidence that prosopagnosia
not

limited to faces


FFA varies in size and location between individuals


FFA also activated for non
-
face objects (e.g. in dog experts)


Alternative hypothesis:


FFA = Flexible Fusiform Area
? (Tarr & Gauthier, 2000)


FFA as a system specialized for fine discriminations / subordinate
categorization


Processes
all complex homogenous objects
(not just faces)


Activation of FFA increases with expertise



According

to

The

Innocence

Project

(
2008
)

"Eyewitness

misidentification

is

the

single

greatest

cause

of

wrongful

convictions

nationwide,

playing

a

role

in

more

than

75
%

of

convictions

overturned

through

DNA

testing
.
"

Still,

the

criminal

justice

system

profoundly

relies

on

eyewitness

identification

and

testimony

for

investigating

and

prosecuting

crimes

(Wells

&

Olson,

2003
)
.

Source: http://www.helium.com/items/1276135
-
accurate
-
eyewitness
-
accounts

Did you know?

What factors affect a person’s memory
and their ability to identify a suspect?


Age

may

play

a

role

in

the

accuracy

of

an

eyewitness’

statement

or

identification

of

a

suspect
.

Studies

have

shown

that

when

a

lineup

contains

the

actual

culprit,

both

young

children

and

elderly

perform

well,

but

when

the

lineup

does

not

contain

the

culprit

there

is

a

higher

rate

of

mistaken

identifications
.


The

race

of

the

witness

may

also

play

a

role
.

The

Cross

Race

Effect

(CRE)

is

a

phenomenon

in

which

people

are

better

at

recognizing

faces

of

their

own

race

rather

than

those

of

other

races
.


The

use

of

drugs

can

alter

a

person’s

ability

to

recall

the

events

of

a

crime

even

after

they

are

no

longer

under

the

influence
.


A

person’s

memory

of

an

event

can

be

influenced

by

other

witnesses,

investigators,

and/or

the

media
.

Investigators

use

open
-
ended

questioning

and

follow

procedures

for

conducting

line
-
ups

to

limit

their

influence

on

a

witness’

memory

of

an

event

or

identification

of

a

suspect
.

Witness Factors

Source: http://www.helium.com/items/1276135
-
accurate
-
eyewitness
-
accounts


A

crime

that

is

extremely

traumatic

for

an

eyewitness

may

affect

his/her

recall

of

the

event
.

For

example,

a

witness

confronted

with

a

weapon

tends

to

focus

on

the

weapon

rather

than

the

perpetrator’s

face
.


Someone

who

is

able

to

focus

on

a

perpetrator's

face

for

a

minute

or

longer

will

tend

to

have

a

more

accurate

memory

than

someone

who

saw

the

person

for

only

a

few

seconds
.



Studies

have

shown

that

faces

that

are

either

highly

attractive,

highly

unattractive,

or

distinctive

are

more

likely

to

be

accurately

recognized
.

Simple

disguises,

such

as

hats

or

sunglasses,

can

interfere

with

accurate

eyewitness

identification
.

However,

body

piercings

and

tattoos

increases

the

likelihood

of

an

accurate

identification
.


The

time

of

day

in

which

the

crime

occurred

as

well

as

a

person’s

view

of

the

scene

may

affect

what

a

he/she

is

able

to

see
.

In

addition,

a

person

who

is

familiar

with

the

area

in

which

the

crime

took

place,

may

have

a

better

recall

of

the

positions

of

the

victims

or

suspects
.


Crime Scene & Suspect Factors

Source: http://www.helium.com/items/1276135
-
accurate
-
eyewitness
-
accounts

Go to:


http://www.innocence
project.org/news/Vide
o
-
Center.php




misidentification


Introduction to Biometrics