Localization of Auditory Stimulus in the Presence of an Auditory Cue

By

Albert Ler

Cuing Paradigm as a Means of Studying Attention

• Visual attention• Visual cuing paradigm:

– Subject needs to react to a stimulus being presented in one of several locations

– Typical result is that target detection is better when a cue primes the subject to the location of the target than without a cue

Visual Cuing Paradigm (cont.)

• 2 orienting mechanisms found:

• Exogenous: take place automatically under pure stimulus control; attention is “pulled” to the location of a salient event

• Endogenous: under strategic control; attention is “pushed” to the location where the target is expected

Auditory Cuing Studies of Auditory Attention

• Very few!• These studies include target detection and target

intensity discrimination • In these studies, no reliable spatial cuing effects

were found

Spence and Driver, 1994

• Cues: 2000Hz tones at 72 dB(A)

• Targets: three 20ms bursts of WN at 85 dB(A), each separated by 20ms gap

Loudspeaker

Spence and Driver, 1994 (cont.)

• 2 main conditions: – 1. Cue and target on the same side 50% of the time

– 2. Cue and target on the same side 75% of the time

• 3 within subjects factors:– Target laterality (left or right)

– SOA between cue and target (100ms, 400 ms, or 1000ms)

– Cue side (cue on the same [valid] or opposite [invalid] side as the target)

Spence and Driver, 1994 (cont.)

• Results:• Subjects quicker to localize a target sound as

being in front of them or behind them when it was immediately preceded by a cue sound on the same side (in both conditions)

• Effect is stronger when cue predicts target 75% of the time

Spence and Driver, 1994 (cont.)

• But…

• They ignored the effect of ITD

Sach et al., 2000

• ITD discrimination task• Sounds were presented over headphones and

lateralized by ITD• Auditory cue was presented before the target

sound

Sach et al., 2000

• Target: pairs of successive sounds lateralized to one or other side, which either shared the same ITD or whose ITDs differed by a threshold amount

• Subjects indicated whether the ITDs of the two sounds were the same or different

• Each trial comprised a cue tone followed 400 ms later by a target click pair, each of which was lateralized to either the left or right

Sach et al., 2000 (cont.)

• 80% of the trials cue and target on the same side• 20% of the trials cue and target on opposite sides

• Results:– Performance was better for signals lateralized on the

expected side of the head

Current study

Current Study (cont.)

• 2 main conditions

• Voluntary (endogenous): Cue and target lateralized to the same side 75% of the time

• Involuntary (exogenous): Cue and target lateralized to the same side 50% of the time

Current Study

• Additional factors:

• Interstimulus intertrial (ISI): aka SOA; 50 ms or 300 ms

• Cues: click or burst (30ms noise burst), 45dB• Stimuli: click or burst (three 30ms burst separated

by 10ms gaps), 45dB

Current study (cont.)

• Total 16 conditions• Each condition consists of 60 measurements

(divided into 2 sessions)

Current study (cont.)

• Hypotheses:• 1. Voluntary condition yield smaller angular

difference than involuntary condition• 2. Valid trials yield smaller angular difference

than invalid trials

• Across subjects analyses are performed using paired-sample t-test (t(2) = 2.92; p < 0.05)

Voluntary - Involuntary

Mean of Voluntary vs. mean of Involuntary conditions

7.4

7.6

7.8

8

8.2

8.4

8.6

8.8

Voluntary Involuntary

me

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• t(2) = 23.12• p < 0.05 (one-tail)

Within Voluntary (mean Valid – mean Invalid)

Within Voluntary Condition: Mean Valid vs. Mean Invalid

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8.2

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Valid Invalid

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• t(2) = -0.77• p > 0.05 (one-tail)

Within Involuntary (mean Valid – mean Invalid)

Within Involuntary: mean Valid - mean Invalid

7.5

7.6

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8.1

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Valid Invalid

Ave

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• t(2) = -0.59• p > 0.05 (one-tail)

Voluntary Valid – Involuntary Valid

Voluntary Valid - Involuntary Valid

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Valid Invalid

Ave

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• t(2) = 4.56• p < 0.05 (one-tail)

Voluntary Invalid – Involuntary Invalid

Voluntary Invalid - Involuntary Invalid

7.67.8

88.2

8.48.6

8.89

9.2

Valid Invalid

Ave

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• t(2) = 5.08• p < 0.05 (one-tail)

Interstimulus Intertrial (300 msec)

Voluntary – Involuntary

t(2) = 10.70

P < 0.05 (one-tail)

Cues

• Click cue (Voluntary – involuntary)• t(2) = 2.69; p > 0.05 (one-tail)

• Burst cue (voluntary – involuntary)• t(2) = 2.19; p> 0.05 (one-tail)

Stimuli

• Burst stimulus (voluntary – involuntary)• t(2) = -2.17; p > 0.05 (one-tail)

• Burst stimulus (Voluntary valid – Voluntary invalid)

• t(2) = -2.70; p > 0.05 (one-tail)

Summary

• Significant difference found between Voluntary and Involuntary conditions, between Voluntary valid and Involuntary valid, between voluntary invalid and involuntary invalid

• 300 ms ISI contributes most to voluntary – involuntary

• Subjects did worse when ISI = 300 ms

• Compare Voluntary valid and Involuntary valid (ISI = 300ms)

• t(2) = 25.02; p < 0.05 (one_tail)• Compare Voluntary invalid and Involuntary

invalid (ISI = 300ms)• t(2) = 5.53; p < 0.05 (one-tail)• Performance much worse on the valid trials.

Why did subjects did worse when ISI=300ms?

• It is possible that the cue might have acted as a distractor. When the ISI was long enough so that strategic attentional control (i.e. endogenous orienting) can take place, the strategic attentional control actually made spatial localization of auditory stimulus worse.

Why did subjects did worse when ISI=300ms?

• Exogenous orienting mechanism involves localization mechanism at the lower brain level and therefore better at locating stimulus

• Endogenous orienting mechanism is noisy and therefore subjects’ performance was worse

Finally…

• No cuing advantage was found across subjects.