Information Density and Structural Complexity in Audio Messages:
Are Two Concepts Better than One?
Robert F. Potter, Zheng Wang, Ashley Sanders-Jackson, Jacob Koruth, Satoko Kurita & Annie Lang
Indiana University
Message Processing as Resource Parsing
This study is a mixed 3 (Information Density) X 2 (Structural
Complexity) x 4 (Message) x 4 (Order) design. Except for Order,
all are within subject factors.
Independent Variables
Information Density
• 3 levels (Low, Medium & High)
• An index of the resources required for processing
Automatic resource allocation occurs via the orienting
response (OR) during both visual (Lang et al, 1999) and
auditory processing (Potter et al, 2001).
These early studies made two assumptions respectively:
1. Some visual structural features always require more resources to process
than others. For example, a cut would always require more resources than
an edit.
2. Each auditory structural feature introduced the same amount of
information for processing.
However, these are probably not valid assumptions. This study addresses the
second assumption by introducing a new concept.
Auditory Information Introduced (Auditory I2)
Identifies two common sets of auditory structural features and quantifies the
relative amount of information needed to be processed by the resources
automatically allocated to it.
The Voice Change:
For each voice change the following questions were asked:
•Is it a new voice, one I that hasn’t been heard before?
•Does it introduce unrelated content?
•Is there a change in auditory form across the voice change?
• To calculate this we first totaled up the Auditory I2 values of all
the voice changes and onsets in each message.
• Then, for each PSA this total was divided by the message
duration to arrive at an Auditory I2/second value.
• This was the operational definition of Information Density.
• The 24 messages were divided into three groups of 8 to create
the 3 levels of the factor.
For each onset the following questions were asked:
•Is this a new form of sound (i.e., have I heard this sound before)?
•Is it unrelated to what has happened in the message?
•Is it an emotionally intense sound?
72
70
low
med
68
hi
66
64
62
60
high
Structural Complexity
Structural Complexity
• 2 levels (Low & High)
•An index of resources allocated to message processing.
•Within each level of information density, messages were divided
into two groups representing the highest and lowest values of
auditory structural onsets per second.
Prior to overload cognitive effort will increase (lower
heart rates) with increases in structural complexity.
As overload occurs, listeners will disengage from
message processing, and heart rates will increase.
Figure 2:
Structural Complexity X Information Density on Heart Rate
Dependent Variables
78.6
Emotional Arousal and Valence measured by the SelfAssessment Manikin (SAM; Bradley & P.J. Lang, 1994).
78.4
78.2
Physiological Arousal assessed by skin conductance responses
(SCRs).
78
Low
Med
Hi
77.8
77.6
77.4
Cognitive Effort measured by change in heart rate over time.
77.2
77
Low
Encoding accessed by a forced-choice, four-alternative, multiplechoice recognition test
Data Collection
•Is there a change in ambience compared to the last time I heard this voice?
Sound effects, music onsets, production effects, silence, and emotional words
74
low
•Is there a change in ambient sound across the voice change?
Structural Onsets:
78
76
•Is there a change in form compared to the last time I heard this voice?
•Is there an emotion change across the voice change?
Figure 1: Structural Complexity X Information Density
on Recognition Memory
High
Structural Complexity
Disengagement from message processing will not
impact physiological arousal levels, however, which
will increase with increases in structural complexity.
Participants
96 undergraduates (36 male, 56 female, 4 unspecified) and
72 tweens (32 male, 29 female, 1 unspecified ). Age ranged
from 9 to 24.
Figure 3:
Structrual Complexity x Info Density on SCR Freq
4.1
4
Procedure
Each participant completed the experiment individually.
They listened to 24 radio PSAs. Following each message,
they rated how they felt during the message using SAM.
After all 24 messages, they performed a distraction task
and then took the recognition test.
3.9
# of SCRs
Structural Features in Earlier Studies
When resources allocated by structural complexity
are greater than resources required by information
density, recognition will increase. When those
required surpass those allocated, the system will
overload and recognition will decrease.
BPM
Resources are allocated automatically as a function of medium and message
structure and when content is motivationally relevant. Users allocate
resources through decisions about what messages to engage with, how hard
to work at them, etc.
Study Design
% correct
The Limited Capacity Model of Motivated Mediated Message Processing
(LC4MP) conceptualizes message processing as an interaction between a
media user, a medium, and message content.
Select Predictions & Results
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low
3.8
med
high
3.7
3.6
3.5
low
high
Structural Complexity
•Is there a change in emotion caused by the sound?