MaskerFirst Advantage in Cued Informational Masking Studies

1
Masker-First Advantage in Cued Informational
Masking Studies Virginia M. Richardsa, Rong
Huanga, and Gerald Kidd Jrb. (a) Department of
Psychology, University of Pennsylvania (b)
Communication Disorders and Hearing Research
Center, Boston University
Previous informational masking studies have
shown that a preview of an upcoming masker
stimulus provides a release from informational
masking whereas a preview of the
signal-plus-masker stimulus does not. In the
following experiments we asked whether this
asymmetry remained when the cue and trial
intervals were random, i.e. when a same/different
two-interval, forced choice task was used.
Yes/No Task
Yes/No Trials
1.6
1.00
Sig Interval
1.4
NoSig Interval
0.90
1.2
0.80
1.0
Prop "int" trials
Prop "int" resp re.
0.8
0.70
Proportion Correct
0.6
0.60
0.4
0.50
1
2
3
4
5
6
0.40
(66)
(91)
ltMgt
ltSMgt
Signal Strength

• Experiment 1
•  
•  
• Observers indicated whether the two intervals of
  a 2IFC trial had the same vs. different stimuli.
  The stimulus was either a masker or a
  signal-plus-masker. The four potential trial
  types are depicted in Figure 1
• ltM Mgt masker in both intervals
• ltSM SMgt signal-plus-masker in both intervals
• ltM SMgt masker followed by signal-plus-masker
• ltSM Mgt signal-plus-masker followed by masker
• Methods
• five observers
• 6-component, randomly drawn masker
• Random masker for each trial same masker
• across intervals

(Percent Correct)
Trial Types

2IFC Trials
2IFC Task
1.6
1.00
Interval 1
1.4
0.90
Interval 2
1.2
ltM Mgt trial
0.80
1.0
Prop "int" trials
Prop "int" resp re.
0.70
Proportion Correct
0.8
0.6
0.60
0.4
0.50
1
2
3
4
5
6
0.40
(66)
Figure 2
(94)
ltM,SMgt
ltSM,Mgt
Signal Strength
ltSM SMgt trial
(Percent Correct)
Trial Types

• Experiment 2
• In this experiment we examined order effects and
  response biases for the detection of a tone added
  to randomly drawn maskers using three procedures
  Yes/No, 2IFC, and 3IFC
• Methods
• Observers 1-4 from experiment 1
• Random maskers for each trial same masker
  across intervals
• 3-down, 1-up adaptive adjustment in signal level
  
• Results
• Figure 3 shows proportion correct, averaged
  across signal levels, for trial types encountered
  in the yes/no, 2IFC, and 3IFC conditions. The
  filled squares show group means.
• Yes/No Proportion correct scores were not
  reliably different
• on masker and
  signal-plus-masker trials
• 2IFC Proportion correct scores were lower
  for ltM SMgt
• than ltSM Mgt trials
• 3IFC Proportion correct scores were lowest
  for ltM, M, SMgt

3IFC Task
3IFC Trials
Frequency
1.6
1.00
Interval 1
1.4
0.90
Interval 2
1.2
0.80
Prop "int" resp re.
Prop "int" trials
1.0
ltM SMgt trial
0.70
Proportion Correct
0.8
0.60
0.6
Interval 3
0.50
0.4
0.40
1
2
3
4
5
6
ltM,M,SMgt
ltM,SM,Mgt
ltSM,M,Mgt
(61)
(94)
Signal Strength
Trial Types
(Percent Correct)
ltSM Mgt trial
Figure 3
Figure 4
Time
Summary and Discussion Past work has shown that
a pre-trial preview of the masker provided
release from informational masking but a preview
of the signal-plus-masker did not. In a similarly
vein, for 2IFC, same/different task observers
were more accurate when the masker was in the
first interval. In contrast, for 2IFC and 3IFC
trials, observers were biased to indicate that
the signal was in the first interval. In these
informational masking studies, observers
decision processes appeared to depend on the
paradigm used. More important, response biases
were obtained in most of the paradigms tested.
Acknowledgements This work was supported by
grant R01 DC 02012 and R01 DC 04545 from the
National Institutes of Health.
Figure 1