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Cognitive
Psychology PSY 504
VU
Lesson
15
PATTERN
RECOGNITION
Feature
Analysis (continued)
Example
There
is fair amount of behavioral
evidence for the existence
of features as components in
pattern
recognition. For instance, if
letters have many features
in common__ as with C and
G___
evidence
suggests that subjects are
particularly prone to confuse
them. When such letters
are
presented
for a very brief interval,
subjects often misclassify
one stimulus as the
other.
Kinney,
Marsetta, & Showman, (1966)
conducted an experiment. In that
experiment they
presented
letters for very brief
intervals.
The
subjects made
29
errors when letter G was
presented
21
involved misclassification as C
6
misclassification as O
1
misclassification as B
1
misclassification as 9
No
other errors occurred
Implications
It
is clear that subjects were
choosing items with similar
features.
C
G O B 9 all share a
curve
Such
a response pattern would be
predicted by a feature analysis
model.
If
subjects can only extract
some of the features during
a short time, they
would
have
difficulty deciding between
letters that share these
features.
Speech
Recognition or Auditory
Recognition
Recognition
of speech poses new
problems. It is more
complex.
Segmentation
is a major problem because
speech is not clearly
demarcated the way written
text
is.
Native speakers always mix
words together in their
speechs. They do it
unconsciously.
It
seems there are clear
gaps between words but
that is an illusion. For
example in urdu;
Kya
haal hay and
kya ho
raha hay
The
person who does not
know Urdu he understands
these words as kyaalay
and kyaoray.
The
speech appears to be continuous
stream of sounds with no
obvious word boundaries. It
is
our
familiarity with our own
language that leads to the
illusion of word
boundaries.
Phonemes
Phonemes
are the basic vocabulary of
speech sounds; it is in terms of
them that we
recognize.
Like,
School
[s]
[k] [u] [l]
43
Cognitive
Psychology PSY 504
VU
S,
K, U, L are phonemes. These
help us in understanding.
Feature
analysis and feature
combination
processes seem to underline
speech perception much as
they do visual
recognition.
As
with individual letters,
individual phonemes can be
analyzed as consisting of a number
of
features.
These are given
below.
1.
Voicing
It
is feature or sound of phonemes
produced by the vibration of
the vocal cords.
Like,
Sip
and zip
[s]
is voiceless
[z]
is voiced
Place
your fingers as you produce
each sound
2.
Place of articulation
It
refers to the place at which
the vocal track is closed or
constricted in the production of
a
phoneme.
It is closed at some point in
the utterance of most
consonants.
Consonant
pronounced using both
lips;
A
consonant pronounced by bringing
both lips into contact
with each other or by
rounding them.
In
English the bilabials
are b, p, m.
and w.
f
and v are labiodentals
because the bottom lip is
pressed against the front
teeth.
t,
d, s, z, n, l are alveolar because
the tongue presses against
the alveolar ridge of the
gums just
behind
the upper front
teeth.
Experiment
Miller
& Nicely (1955) presented
consonants in noise
Voiced
Voiceless
Bilabial
[b]
[p]
Alveolar
[d]
[t]
b
is voiced and p is voiceless. d
and t are identical in case
of articulation. They
presented
letters
with noise.
Results
Subjects
exhibited confusion and
reported hearing one sound
when actually another sound
had
been
presented
Experimenters
were interested in which
sound was confused with
which
Feature
analysis model would predict
more confusion with sounds
that differed by only a
single
feature.
When
presented with [p], subjects
more often thought that
they heard [t] than
that they heard
[d].
The
phoneme [t] differs from
[p] only in terms of place
of articulation, whereas the
[d] differs in
both
place of articulation and
voicing. Similarly subjects
presented with [b] more
often thought
they
heard [p] than
[t].
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