RESPONSE TIMES OF ODONTOCETE CETACEANS IN AUDIOMETRIC TESTS

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RESPONSE TIMES OF ODONTOCETE CETACEANS IN
AUDIOMETRIC TESTS

• Diane J. Blackwood

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Overview

• Response Time review
• Hearing Test
• Subject Species
• Methods
• Results
• Listening Task
• Comparison of Results
• Conclusions

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Response Times

• Interval from the beginning of a stimulus to the
  beginning of the subjects response
• Work has been done on humans, some terrestrial
  mammals and some birds
• Response times provide information about
  perceptual processes
• Response times for this study were collected as
  part of an audiometric test of cetaceans and
  during a separate listening task

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Response Time History

• 1700s Astronomy human RT
• 1850 Helmholtz measures nerve conduction with RT
• 1868 Donders subtractive method to cognitive
  function
• 1913 Well review
• 1930 Loudness defined
• 1948 Shannon Information Theory
• 1953 Hick Hyman Choice Reaction Times
• 1960 Use on non-verbal humans and faking
• 1960s and 1970s Applied to non-humans

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Response Time vs. Stimulus Amplitude (humans)
Kohfeld, Santee Wallace (1981)
from Kohfeld, Santee Wallace (1981)
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Loudness and Latency Curves
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Methods Hearing Test

• Masked hearing tests
• Six frequencies from 400 Hz to 30 kHz
• Method of Free Response
• Staircase method of stimulus presentation
• Reversal criterion
• Automated response detection
• Analysis
• Analyzed 53,763 responses where human computer
  algorithm agreed
• Response times vs test tone amplitude

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Subjects hearing test
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Sam H. Ridgway
NOC
MUK
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Atlantic Bottlenose Dolphin
(Tursiops truncatus)
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Audiograms(bottlenose dolphins white whales)
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Hearing Test with Multiple Dives
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Timing for Hearing Tasks
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Screen 2 Correctly found low intensity response
NOC84A00.Pix.11
Screen 3 Incorrectly missed response buried in
pulses
NOC86005.Pix.11
Screen 4 Autodetect scored part of pulse as
response
NOC85105.Pix.11
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BEN86H01.Pix.1t
Screen 5 Correctly indicated no-response to
visible tone
BEN86T01.Pix.4
Screen 6 Correctly found response after visible
tone
NEM81E02.Pix.15
Screen 7 Correctly indicated no-response with
large bust pulse
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Classification Performance
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Hearing Test Frequency Polygon
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SRT - Hearing Test
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Hearing Test - Allometry
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Whistle Amplitude Hearing Test
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Whistle Length Hearing Test
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Effects of Masking Level
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Response Time BEN 4.5 kHz
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Response Time MUK 6 kHz
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Response Time - NEM
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Listening Task

• The listening task was actually done first.
• Stimuli were well above threshold.
• Stimuli varied in amplitude, duration and
  frequency.
• No masking noise.

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Listening Subject Data
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Listening Frequency Polygon
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Listening
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Listening
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Listening
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Multiple Frequencies as more information or a
complex task

• Both of my studies were Simple Response Time
• Others studies have looked at Choice Response
  Time
• Hick and Hyman (1953) suggested Choice Response
  Time increases with increasing numbers of choices
  
• Do multiple frequency data sets convey more
  information?

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APR at 100 ms 40 kHz
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MAU 40kHz 100ms
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MAY 40kHz 100ms
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SLA 40kHz 100ms
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TOD 40kHz 100ms
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Effects of Duration
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MAU 40kHz
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MAY 120 dB
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Increased Response Time to High Frequency Stimuli

• Two subjects MAU and MAY showed greatly increased
  response time to high frequencies
• These two dolphins were later tested and found to
  have a hearing loss at these frequencies.
• This shift in response time is consistent with
  response times as a reflection of perceived
  loudness.

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MAU 100ms 120dB
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MAY 100ms duration
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Comparison of Listening Task and Hearing Test
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Compare Dolphins
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Compare Whales
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Listening Task vs Hearing Test
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Hearing Test

• Response time generally decreased with increasing
  tone amplitude as in terrestrial animals.
• First look at the effect of masking noise on
  response times in marine mammals.
• Masking shifted hearing threshold and response
  times to high amplitude stimuli, response times
  were similar relative to threshold.

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Listening Task

• The listening task looked at SRT well above
  threshold
• There was no masking noise
• Varied Duration, Frequency Amplitude of test
  tones
• Effect of duration not clear, but duration did
  not vary within the same session

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Discussion

• Differences between species
• - suggestive of longer transmit times for a
  larger animal?
• - Or differences in life history
• -- prey type
• -- movement types, in-air jumps

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Conclusions

• Bottlenose dolphins have shorter response times
  (410 ms) than white whales (670 ms) in a
  hearing test
• Bottlenose dolphins have shorter response times
  (230ms) than white whales (580ms) during a
  listening task
• Subjects were faster and more consistent after
  training
• Increased masking noise shifts both threshold and
  response times.
• Animals were faster within a notch in the masking
  noise

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Cont.

• Response times are indicative of timing of
  perceptual and motor processes in the subjects
• Response times may be used as estimates of
  perception of loudness
• Effects of masking noise may be similar to
  natural and anthropogenic noise in the ocean.

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Acknowledgments

• Our funding sponsor, Tim McBride, Program
  Executive Office, USW
• Don Carder Carolyn Schlundt
• Trainers Tricia Kamolnick, Mark Todd, Jennifer
  Carr, Monica Chaplin
• Computer support Wesley Elsberry Jim Finneran

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