Testing Two Cue Theory and the Cocktail

8/14/2019 Testing Two Cue Theory and the Cocktail

1/20

Testing Two Cue Theory and the Cocktail

Party Effect of Familiar and Unfamiliar

Sounds on Hearing

Alan Cummins Student No: 1165236 Course: PSY283 Lecturer: Dr. Garry Prentice


2/20

Laboratories II PSY283 Alan Cummins 1165236 Page 2 of 20

Abstract

This experiment seeks to determine whether inter-aural time differences and inter-aural level difference

have an affect on the location of sound. In addition this experiment seeks to determine if attentional

cues help in correct location of sound. Participants were placed inside a diamond of assistants who were

precisely positioned to test ITD and ILD as indicated in previous work by Strutt (1877). Familiar and

unfamiliar sounds in the form of names and rattles respectively were used to provide attentional cues to

the participants and aid them in correctly locating sounds. Fifteen participants took part in a repeated

measure within subjects designed experiment in order to test these hypotheses. The dependent variable

is that of the percentage of correct responses in determining sound location. The independent variable

was that of the use of familiar (names) versus unfamiliar (rattle) sounds. The experiment seeks to verify

that there will be a difference in the correct response of sound position for position 1 and 5 versus all

other positions. This builds on work by Bellamy (1993). It also seeks to verify that there will be a

difference in the correct response of sound position for familiar versus unfamiliar sounds, making use of

REFERENCE attentional cues. The experiment fails to maintain a consistent and obersevably different

set of sounds in order to correctly test the hypotheses suggested. It can be extended into determining

hat situational factors, in terms of attentional cues, may be used to either enhance or decrease the

correct location of sound.


3/20


ContentsAbstract ......................................................................................................................................................... 2

Introduction .................................................................................................................................................. 4

Method ......................................................................................................................................................... 7

Results ......................................................................................................................................................... 11

Discussion.................................................................................................................................................... 14

References .................................................................................................................................................. 17

Appendix A Circular Location of Noisemakers ......................................................................................... 18

Appendix B Data Collection Chart ............................................................................................................ 19

Appendix C SPSS Output .......................................................................................................................... 20


4/20


Introduction

Sound is produced in the form of vibrations, changes in pressure that are both cyclical and in waves.

These sound waves are collected by the outer ear, via the pinna (See Figure 1). The pinna has a unique

shape which allows the funnelling of sound down the ear canal to the eardrum.

Pinna (outer Ear)

Ear Drum

Hammer

Anvil

Stirup

Auditory Nerve

Cochlea

Figure 1 - Human Ear

These sound vibrations cause the inner ear to vibrate and cause movement in the ossicles structure

which is made up of the hammer, anvil and stirrup. This movement cause waves in fluid in the cochlea,

these waves are sensed by the Basilar membrane and in turn cause the hair-cells of the Organ of Corti to

be stimulated and the vibrations are finally turned into nerve impulses which pass along the Auditory

nerve to the brain. Pure tones have a frequency and intensity which as Beaumont (1988) has discussed

can be extrapolated out to complex real sounds. Location of sound is calculated according to several


5/20


cues including Azimuth phase and intensity differences, head movements, pinna effects and

reverberation. Experimentation was carried out by Bellamy (1993) in order to test participants

capabilities of locating sound under varying directions. The main cues considered were that of inter-

aural time difference (ITD) and inter-aural level difference (ILD). ITD refers to the difference in time

between sound vibrations reaching one ear over the other. The coincidence detection model of Jeffress

(1948) is an accepted model for low-frequency sound localisation. Low frequency sound is best picked

up by ITD. ILD refers to the difference between frequencies between one ear and another when

listening to a sound. Both cues are incorporated into Rayleighs Duplex Theory, Strutt (1877), or the two

cue theory. This states that for low frequency tones ITD is used to locate sound while high frequency

tones are located by ILD. Sound detection and location is a psychological event with an interaction of

physical, biological and psychological factors as suggested by the signal detection theory. This

experiment builds on previous work by Bellamy (1993) and incorporating testing of ITD and ILD in

locating sound and uses attentional cues to determine if they aid in location of familiar sound. Attention

is used to focus on particular parts of the environment, namely sound and its location, in the case of this

experiment. The experiment seeks to use selected or focused attention to aid in sound location by use

of a familiar sound that of a participants name. This grabbing of the participants attention has been

investigated byCherry (1953)with the use of a cocktail party effect. It was found that people paid more

attention to stimuli when it directly incorporated information personal to them. The experiment seeks

to investigate two hypotheses:

Alternate Hypothesis One: There will be a significant difference between the percentage correct

identification of noise position between positions 1 and 5 as compared to all other positions on

noisemakers, namely that there will be a reduction in correct identification of sound position when

coming from position 1 and 5. (See Figure 3 for Positional Diagram)


6/20


Alternate Hypothesis Two: There will be a significant difference between the percentage correct

identification of noise position across all available noisemaker positions when comparing the familiar

sound of a participants name with an unfamiliar sound of a rattle.

By testing the hypotheses put forward the experiment seeks to add further weight to that of the two

cue theory and extend it further to incorporate attentional cognitive processes.


7/20


Method

Materials:

The materials used for the experiment were as follows:

Name sheet: To record name of each participant. Data Collection sheet: To record the correct or incorrect response for each of familiar and

unfamiliar sounds

Rattle: Simple rattle shakers were given to each assistant to make the unfamiliar sound. Instruction set: Script explaining how the experiment would be carried out. Order Sheet: Random assigned order sheet for each assistant to know when they should make a

sound.

Seats: For the participant to sit on and the correctly arranged chairs for the assistants. Laboratory: As sound was being used, a quiet laboratory with no distractions was used.

Blind-fold

Chips: For random order assignment of participants and for those who would become assistants.Participants:

The total sample size of fifteen participants was taken from Psychology Students from Dublin Business

School (n=15). There were a further eight participants who took part as assistants to the experimenter

and carried out the noisemaking duties. These were also randomly chosen from DBS psychology

students.

Design:


8/20


The design method used for this experiment was a repeated measures within subjects design. This

consisted of one group of participants who carried out an experiment listening to and detecting position

of a familiar sound, in the form of their name being called out and then a second experiment under the

same circumstances but with an unfamiliar sound used, in the form of a shaker rattle. The dependent

variable was the percentage correct identification of the sound position. The independent variable was

the use of names or rattle as the sound for detection.

Procedure:

1. A group of 8 assistants, required to make sounds for other participants to detect, wererandomly chosen from the total set of participants.

2. The experiment participants were randomly assigned an order in which to enter the experimentby choosing from a set of cards.

3. Upon being assigned an order, each participant filled out a name sheet so that their name couldbe used as the familiar sound. They were instructed that their name would only be used within

the experiment and would not be quoted during the subsequent publication and reporting of

results.

4. Instructions were read out as follows: You will be blindfolded and led into the experiment roomand sat on a chair. Around you eight sounds will be made. Please point clearly in the direction

you think the sound is coming from. Then place your arms by your side and await the next

sound. Do not move your head at any time and keep looking forward. Once all eight sounds

have been made, you will be led back out of the experiment room and your blind-fold removed.

Please do not tell any of the other participants any details of your experiment. You will be

carrying out the experiment twice and will be instructed as to when your turn comes about.


9/20


5. The name of the next participant was given to all the experimenters for use as the familiarsound.

6. Each participant was blind-folded outside of the experiment room and then led into theexperiment room and seated.

7. A prior agreed random order of position of sound to be made by experimenters was put intoprocess, with each experimenter in turn calling out the name of the participant.

8. Each experimenter in turn called out the name of the participant and awaited the participantsindication of the position the sound had been made from.

9. Once they had indicated the position and returned their hands to their side the nextexperimenter briefly paused and then called out the familiar sound from their respective

position. This was carried out until all eight experimenters had called out the participant name

from a random order of position.

10.As the participant indicated the position of the sound an experimenter noted their correct orincorrect response (1 or 0) on the data-collection sheet. There was a separate data sheet used

for familiar and unfamiliar sounds. (See Table 1)

11.Once all eight positions had been covered the participant was given indication that theexperiment had ended and led back out of the experiment room.

12.This process was carried out twice for each participant having to carry out the experiment forboth unfamiliar and familiar sounds.

13.When carrying out the second part of the experiment with an unfamiliar sound the assistantswere given a rattle shaker with which to make the sound. All other parts of the process

remained the same.


10/20


14.The participants were thanked for their participation at the end of the two parts of theexperiment and asked to not discuss the experiment, procedures and instructions with any

other participants.

15.Once all participants had carried out the experiment the data collection sheets were tallied andmatched for each participant for their response to a familiar and an unfamiliar sound.


11/20


Results

The number of correct detections of sound position were calculated as a percentage of the total number

of participants for each of the eight positions in the experiment. This calculation was carried out for

each position and for each sound, namely familiar and unfamiliar. The percentage results for each are

displayed in Figure 2.

Figure 2 Sound-type By Percentage Correct Detection Comparison

Looking at these results positions 1 and 5 (See Figure 3) should have had a lower percentage correct

identification, however looking across all positions there is a minimal difference in the percentage

correct response. Looking more closely at positions 3 and 4 it should be noted that there was a lower

percentage correct response for these positions for the familiar sound than at position 1 and 5.

n1 = 93.3%, n5 = 86.7% compared to n3 = 73.3%, n4 = 73.3%

93.380

10086.7

73.3

100

73.3

93.3 86.7 93.3100 93.3 100 100 93.3 86.7

0

10

20

30

40

50

60

70

80

90

100

n1 r1 n2 r2 n3 r3 n4 r4 n5 r5 n6 r6 n7 r7 n8 r8

PercentofCorrectResponses

Sound Type

n = Name

r = Rattle

Sound Type By Percentage Correct Detection

Comparison


12/20


Individually comparing familiar (n) versus unfamiliar (r) scores for each position 1 to 8 there is only

minor differences between them, again, only positions 3 and 4 having a large difference in correct

response.

n3 = 73.3% versus r3 = 100%

n4 =73.3% versus r4 = 100%

Comparing the mean correct response across all positions for familiar versus unfamiliar sounds it can be

seen that there is a very small difference detected.

Mean of Correct Response Familiar Sound = 7.2

Mean of Correct Response Unfamiliar Sound = 7.333

The standard deviation gives some indication that there are differences in the spread of number of

correct answers with a greater variation in correct responses for unfamiliar sounds as indicated by a

larger standard deviation score.

Std. Deviation Correct Responses Familiar =0 .86189

Std. Deviation Correct Response Unfamiliar = 1.46554

A Wilcoxon test was carried out (See Figure 5) in order to make a comparison of the familiar versus

unfamiliar mean correct response and determine if a significant difference could be detected.

Z = -0.686, P = 0.49, P > 0.05, 2-tailed


13/20


This indicates that there is no significant difference between percentage correct determination of sound

position when comparing familiar versus unfamiliar sounds.


14/20


Discussion

It was found that there was no support added to the Bellamy (1993) experiment. The first

hypothesis stated that there would be a significant difference in the correct location of sound between

positions one and five as compared to all other positions. This wished to add weight to ITD and ILD as

discussed in the two cue theory. It was expected that sound travelling directly in front or behind a

participant would reach both ears at the same time and in doing so make it difficult to pick up on the

location of the sound. Neither left nor right ear would be able to determine which had received stimulus

input first. The null hypothesis was not rejected and it was shown that there is no significant difference

in the number of correct responses at each of the eight positions as set up in the experiment. With

regard to the second hypothesis it was found that there was no significant difference between the

correct location of sound when comparing familiar versus unfamiliar sounds. This wished to make use

of attentional cues in the form of participants names to focus attention and increase the likelihood of

correctly location a sound. It was found that the null hypothesis could not be rejected.

Both hypotheses and the experiment carried out may have fallen foul of situational effects such as

interference from outside noise, sensitivity of the participants general hearing ability, the focus and

motivation of the participant and their expectations of carrying out such as experiment. It may have

been the case that the experiment was incorrectly setup with experimenters failing to take heed of

factors such as just-noticeable difference, difference threshold and absolute threshold for hearing.

These varying difference measurements require a base level of volume to be used in order to ensure

that a reasonable difference can be detected. This would be affected by the size of the room, the level

of noise made by the rattlers, the level of voice of each of the eight positions and ambient room noise.

In order to improve upon this experiment these factors need to be addressed. Familiar and unfamiliar

sounds could be pre-recorded and set to a base level as determined by a separate experiment into just-


15/20


noticeable difference. This would reduce variability of sounds made. Focus, motivation and expectation

of the participants may have caused the results to become distorted. As Foot and Sanford (2004)

suggests students and in particular psychology students are not true random participants in any

experiment if they are the only pool chosen from. The participants were aware of the expectations of

the experiment and may have lost or gained focus because of this prior knowledge. Also as participants

were randomly assigned as assistants in the experiment in order to generate familiar and unfamiliar

sounds it can be reasonably suggested that some participants had additional attentional cues in terms of

knowing the voice of assistants. This could increase the attentional focus of a participants brain to one

particular position from the eight sound locations chosen. Looking at position three and four there was a

large discrepancy in the number of correct responses as compared across the other six positions. This

could have been due to those assistants volume or accents. The choice of sounds made for both familiar

and unfamiliar sounds should also be investigated. Simple mispronunciation of a name would render it

as unfamiliar. Equally a rattle may not be considered as significantly unfamiliar as compared to a name.

Despite failing to reject the null hypotheses the experiment has merit in terms of extension into

further attentional studies. The experiment could be extended out to look at Dual task attention such as

detailed by Norman and Shallice (1986) and how it relates to location of sound. Mixture of sounds both

familiar and unfamiliar could be played for participants to determine the limits of attention under such

circumstances. The current experiment blindfolded the participants in order to avoid distraction and

ease of locating the sound. It may be useful to distract the participants with visual images in order to

determine if sound location is effected by such additional stimuli. The type of voice used in the

generation of the familiar sound could also be considered for investigation. It could be varied in terms of

volume, sex, emotional content to determine if sound location is aided. Driver and Spence (1998) have

already carried out work on determining how different modalities can positively and negatively affect


16/20


attention. This work could be incorporated into a revised version of the experiment to see how such

mixtures of modalities affect sound location.


17/20


References

Beaumont, J.G. (1988) Understanding Neruorpsychology. Oxford: Blackwell.

Bellamy, M.L. (1993), Hearing in the Dark. The Society for Neuroscience and the National Association of

Biology Teachers, The Society for Neuroscience and the National Association of Biology Teachers.

Cherry, E.C. (1953). Some experiments on the recognition of speech with one and two ears. Journal of

the Acoustical Society of America, 25, pp 975-979.

Driver, J., & Spence, C. (1998). Attention and the crossmodal construction of space. Trends in Cognitive

Sciences, 2, pp 254-262.

Foot, H., & Sanford, A. (2004). The use and abuse of student participants. The Psychologist, Vol 17, No. 5,

pp 256-259.

Jeffress, L.A. 1948. A Place Theory of Sound Localization. Journal of Comparative and Physiological

Psychology. 41, 35-39.

Norman, D.A., & Shallice, T. (1986). Attention to action: Willed and automatic control of behaviour. In

R.J. Davidson, G.E. Schwartz, & D. Shapiro (Eds), The design of everyday things. New York:

Doubleday.

Strutt, J.W. (1877). The Theory of Sound, Vol 1. London Macmillan.


18/20


Appendix A Circular Location of Noisemakers

A = Listener Sitting in direction of Arrow Indicated

* Arrows Indicate Position and direction of Participants

** Positions 1,3,5,7 are directly in front, right, behind or left of Listener

*** Positions 2,4,6,8 are at 45 Degree Angles From the Listener

1

2

3

8

7

6

5

4

A

Figure 3 Circular Location of Noisemakers in Relation to the Listener


19/20


Appendix B Data Collection Chart

Subject Experimental Location

1 2 3 4 5 6 7 8

Total correct

% Correct

Table 1- Data Collection Chart


20/20


Appendix C SPSS Output

Figure 4 - Frequencies for Recored Correct Participant Responses

Wilcoxon Signed Ranks Test

Figure 5 - Wilcoxon Signed Rank Test

Statistics

15 15

0 0

7.2000 7.3333

.86189 1.04654

Valid

Missing

N

Mean

Std. Deviation

Names Rattles

Test Statisticsb

-.686a

.493

Z

Asymp. Sig. (2-tailed)

Rattles -

Names

Based on negative ranks.a.

Wilcoxon Signed Ranks Testb.

Documents

Testing Two Cue Theory and the Cocktail