<s>
Electronic	B-Application
fluency	I-Application
devices	I-Application
(	O
also	O
known	O
as	O
assistive	O
devices	O
,	O
electronic	O
aids	O
,	O
altered	O
auditory	O
feedback	O
devices	O
and	O
altered	O
feedback	O
devices	O
)	O
are	O
electronic	O
devices	O
intended	O
to	O
improve	O
the	O
fluency	O
of	O
persons	O
who	O
stutter	O
.	O
</s>
<s>
Most	O
electronic	B-Application
fluency	I-Application
devices	I-Application
change	O
the	O
sound	O
of	O
the	O
user	O
's	O
voice	O
in	O
his	O
or	O
her	O
ear	O
.	O
</s>
<s>
Electronic	B-Application
fluency	I-Application
devices	I-Application
can	O
be	O
divided	O
into	O
two	O
basic	O
categories	O
:	O
</s>
<s>
Interest	O
in	O
masking	O
reduced	O
during	O
the	O
1980s	O
as	O
a	O
result	O
of	O
studies	O
finding	O
delayed	B-Architecture
auditory	I-Architecture
feedback	I-Architecture
and	O
frequency	O
altered	O
feedback	O
were	O
more	O
effective	O
in	O
reducing	O
stuttering	O
.	O
</s>
<s>
The	O
effect	O
of	O
delayed	B-Architecture
auditory	I-Architecture
feedback	I-Architecture
(	O
DAF	O
)	O
in	O
reducing	O
stuttering	O
has	O
been	O
noted	O
since	O
the	O
1950s	O
.	O
</s>
<s>
Delayed	B-Architecture
auditory	I-Architecture
feedback	I-Architecture
presented	O
binaurally	O
(	O
i.e.	O
</s>
<s>
Studies	O
have	O
shown	O
that	O
altered	O
auditory	O
feedback	O
(	O
including	O
delayed	B-Architecture
auditory	I-Architecture
feedback	I-Architecture
,	O
frequency	O
altered	O
feedback	O
)	O
as	O
provided	O
by	O
devices	O
such	O
as	O
the	O
Casa	O
Futura	O
School	O
DAF	O
machine	O
or	O
SpeechEasy	O
can	O
immediately	O
reduce	O
stuttering	O
by	O
40	O
–	O
80%	O
in	O
reading	O
tasks	O
.	O
</s>
<s>
Laboratory	O
studies	O
suggest	O
that	O
reductions	O
in	O
stuttering	O
with	O
an	O
electronic	B-Application
fluency	I-Application
device	I-Application
can	O
occur	O
without	O
a	O
reduced	O
speech	O
rate	O
,	O
and	O
that	O
speech	O
naturalness	O
is	O
often	O
enhanced	O
with	O
AAF	O
.	O
</s>
<s>
a	O
reduction	O
in	O
stuttering	O
after	O
the	O
stutterer	O
removes	O
an	O
electronic	B-Application
fluency	I-Application
device	I-Application
,	O
while	O
others	O
have	O
not	O
.	O
</s>
<s>
The	O
effective	O
of	O
electronic	B-Application
fluency	I-Application
devices	I-Application
as	O
measured	O
by	O
qualitative	O
measures	O
and	O
ratings	O
by	O
stutterers	O
have	O
also	O
been	O
made	O
.	O
</s>
<s>
However	O
,	O
positron	B-Application
emission	I-Application
tomography	I-Application
studies	O
on	O
choral	O
reading	O
in	O
stutterers	O
suggest	O
that	O
AAF	O
also	O
made	O
changes	O
in	O
motor	O
and	O
speech	O
production	O
areas	O
of	O
the	O
brain	O
,	O
as	O
well	O
as	O
the	O
auditory	O
processing	O
areas	O
.	O
</s>
