Cognitive Effort and Perception of
Speech by Cochlear Implant Users
Brad Rakerd1
Rana Alkhamra1,3
Terry Zwolan2
Jerry Punch1
Jill Elfenbein1
1Michigan
State University
2University
of Michigan
3University
of Jordan
ASHA 2011
San Diego, CA
Adult CI Users: A Cognitive Effort Survey
n = 127
-- Alkhamra, 2010
Perception in General

Unfolds in real time.

Continuously updates.

Can be remarkably detailed.
Determining Factors

“Top-Down”
–
Partially determined by
higher-level though
processes.
&

“Bottom-Up”
–
Partially determined by
information provided by
the senses.
Perception
Perception: Largely Bottom-Up

Sensory information is
clear, specific, and persuasive.

Limited need for interpretation.

Widespread agreement among
perceivers.
Perception Bottom-Up: “Newts”
Ambiguous
Distorted
Degraded
Speech in Noise
Perception Top-Down: Context Effects
Influenced by Knowledge & Experience

Physicians become expert at reading x-rays.

Frequent Commuters can recognize
announcements about upcoming stops that
novice listeners do not understand.

Native speakers of a language can hear
sound patterns that non-native listeners may
overlook.
Broadbent (1958): Cognitive Effort

Argued that when evaluating a speech
communication channel (e.g., radio)
should consider:
–
Intelligibility of the speech.
–
Ease of listening.
o Revealed
in the listener’s ability to
multi-task.
Speech-Language Processing is Multi-Task

(1) Speech Task: Word recognition.

(2) MemoryTask: Word recall.
–

Key variable: Presence/Absence of
noise.
Notable Finding: Listening in noise
required added cognitive effort for (1) and
impaired performance on (2).
-- Rabbitt, 1966
Cognitive Effort & Presbyacusis
-- McCoy et al. (2005)
A Cognitive Benefit of Hearing Aids
-- Downs (1982)
Adult CI Users: Subjective Reports
n = 127
-- Alkhamra, 2010
Present Study: An Objective Test

Presented speech to adult CI users in
quiet and in increasing background
noise.

Assessed:
– (1) Intelligibility of the speech.
– (2) Cognitive effort required.

Comparison group of adult listeners
with normal hearing (NH).
The Speech Task

Listen to and repeat back
sentences.

32 sentences per test.

Scored for accuracy of reporting of
3-4 key words in each sentence.
Quiet
+15 dB S/N
+5 dB S/N
Task Two: Visual Monitoring

Continuously monitor for a large “X”
that appeared randomly on a
computer screen.

Press a button as soon as possible
after it appeared.

24 presentations per test.

Scored for reaction time.
Single-Task & Dual-Task Tests

Each task performed alone to get a
“baseline” score.

Both tasks performed together to
assess cognitive effort.
–
Expected Trade-off: Devoting greater effort to
the speech task should slow visual reaction
times.
Expt 1: Favorable Listening Conditions
 Single-task
 Dual-task
tests.
Tests:
(1) Speech in quiet.
– (2) Speech in low-level noise
–
o (s/n
= +15 dB).
 12
adult CI users
 14
adults with normal hearing
The Speech Task (NH)
The Visual Monitoring Task (NH)
NH Group
The Speech Task (CI users)
The Visual Monitoring Task (CI)
CI Group
CI Group
Speech Task: Higher Noise Levels
+10
+5
0
Speech Task: Higher Noise Levels
+10
+5
0
Age-matched Listeners