176
averaged to estimate the true absolute threshold. The method of limits has been used
to assess fi sh hearing in psychoacoustic studies that use cardiac conditioning (Fay
1970 ), avoidance conditioning (Tavolga and Wodinsky 1963 ), and operant conditioning (Casper et al. 2003 ). The advantage of using this stimulus presentation
method over the method of constant stimuli is that only a subset of stimuli is required
to determine threshold. However, in psychoacoustic studies using the ASR where
habituation is an issue, the method of limits is problematic. In the descending
method of limits, repeated presentations of the same stimulus can lead to habituation with an earlier than expected cessation of response, which can lead to an incorrect estimation of auditory threshold.
4.4 Adaptive Procedures
Adaptive procedures are experimental stimulus presentation paradigms where the
stimulus parameter presented is dependent on the response of the animal being
tested to the previous stimulus. Unlike the methods of limits and constant stimuli,
adaptive procedures allow for testing of a range of parameters (e.g., frequency and
sound level) that has not previously been specifi ed. For example, in the case of
absolute threshold determination, the experimenter can begin the testing procedure
at any sound level and converge onto a threshold. Adaptive procedures are also
robust and less susceptible to sequential errors that occur with the method of constant stimuli or the method of limits (Woodworth and Schlosberg 1972 ). Sequential
errors, or errors of perseverance, are errors committed by over-responding to a
sequence of stimuli. For example, using the descending method of limits may result
in some false positive sub-threshold responses simply because of repeated responses
to previous supra-threshold stimuli.
4.4.1 Staircase Method
The staircase method has been a stimulus presentation method in use in fi sh studies
since the 1960s (e.g., see Tavolga and Wodinsky 1963 ), but is used less often than
the methods of limits and constant stimuli. The staircase method was developed for
audiometric testing in humans (Békésy 1947 ) and has been adapted for use with fi sh
to determine auditory thresholds (Popper 1972 ), frequency discrimination (Jacobs
and Tavolga 1968 ), and auditory masking (Popper and Clarke 1979 ).
The procedure begins with a presentation of a high intensity stimulus, similar to
the descending method of limits. The stimulus intensity is lowered until the evoked
behavioral response ceases, at which point the stimulus intensity reverts to the previous stimulus intensity presented (reversal of staircase). Staircases are reversed
each time there is a shift from a series of evoked responses to a non-response. There
are multiple variants of the staircase procedure that determine when to reverse stimuli. These follow an “ N up, one down” framework, where N is the number of correct
A.A. Bhandiwad and J.A. Sisneros
averaged to estimate the true absolute threshold. The method of limits has been used
to assess fi sh hearing in psychoacoustic studies that use cardiac conditioning (Fay
1970 ), avoidance conditioning (Tavolga and Wodinsky 1963 ), and operant conditioning (Casper et al. 2003 ). The advantage of using this stimulus presentation
method over the method of constant stimuli is that only a subset of stimuli is required
to determine threshold. However, in psychoacoustic studies using the ASR where
habituation is an issue, the method of limits is problematic. In the descending
method of limits, repeated presentations of the same stimulus can lead to habituation with an earlier than expected cessation of response, which can lead to an incorrect estimation of auditory threshold.
4.4 Adaptive Procedures
Adaptive procedures are experimental stimulus presentation paradigms where the
stimulus parameter presented is dependent on the response of the animal being
tested to the previous stimulus. Unlike the methods of limits and constant stimuli,
adaptive procedures allow for testing of a range of parameters (e.g., frequency and
sound level) that has not previously been specifi ed. For example, in the case of
absolute threshold determination, the experimenter can begin the testing procedure
at any sound level and converge onto a threshold. Adaptive procedures are also
robust and less susceptible to sequential errors that occur with the method of constant stimuli or the method of limits (Woodworth and Schlosberg 1972 ). Sequential
errors, or errors of perseverance, are errors committed by over-responding to a
sequence of stimuli. For example, using the descending method of limits may result
in some false positive sub-threshold responses simply because of repeated responses
to previous supra-threshold stimuli.
4.4.1 Staircase Method
The staircase method has been a stimulus presentation method in use in fi sh studies
since the 1960s (e.g., see Tavolga and Wodinsky 1963 ), but is used less often than
the methods of limits and constant stimuli. The staircase method was developed for
audiometric testing in humans (Békésy 1947 ) and has been adapted for use with fi sh
to determine auditory thresholds (Popper 1972 ), frequency discrimination (Jacobs
and Tavolga 1968 ), and auditory masking (Popper and Clarke 1979 ).
The procedure begins with a presentation of a high intensity stimulus, similar to
the descending method of limits. The stimulus intensity is lowered until the evoked
behavioral response ceases, at which point the stimulus intensity reverts to the previous stimulus intensity presented (reversal of staircase). Staircases are reversed
each time there is a shift from a series of evoked responses to a non-response. There
are multiple variants of the staircase procedure that determine when to reverse stimuli. These follow an “ N up, one down” framework, where N is the number of correct
A.A. Bhandiwad and J.A. Sisneros