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Source Perception
Source Perception and Electrodermal Activity
By
No-Kon Heo
&
S. Shyam Sundar
College of Communications
Penn State University
425, Waupelani Drive, Apt. # 309
State College, PA 16801
Voice: (814) 231-0918
Fax: (814) 863-8044
E-Mail: [log in to unmask]
y For General Competition. Paper submitted to the Communication Theory
& Methodology Division to be considered for presentation at the annual
conference of the Association for Education in Journalism and Mass
Communication, Baltimore, August 5-8, 1998.
y The first author is a doctoral student and the second author is an
assistant professor at the Penn State College of Communications.
y RUNNING HEAD: Source Perception
Source Perception and Electrodermal Activity
A B S T R A C T
The Multistage Sequential Model of Face Recognition was used to hypothesize a
relationship between electrodermal activity evoked by various communication
sources and audience perception of those sources. Skin conductance responses
(SCRs) were recorded while subjects (N = 28) watched images of 22 communication
sources. Perceptions of sources were recorded via a questionnaire. Results
showed that sources associated with different program genres evoked different
levels of SCRs, and familiarity of sources was positively associated with the
level of electrodermal activity.
RUNNING HEAD: Source Perception
Source Perception and Electrodermal Activity
The psychological effects of communication sources have been extensively
studied by scholars in communications, advertising, political communications,
and psychology (for a review, see Wilson & Sherell, 1993). Much of the work on
source effects has manipulated communicator characteristics to assess audience's
attentional biases to communicators and their acceptance of the messages they
deliver. For instance, in previous source-effects studies, message sources have
typically been presented as communicators who are credible versus not-credible;
physically attractive versus unattractive; or ideologically similar versus
dissimilar (Wilson & Sherell, 1993). These source characteristics have been
found to enhance or diminish the message potential to achieve attitude or belief
changes (Chaiken, 1979; Sternthal, Phillips, & Dholakia, 1978).
However, little is known about perception of sources as a function of emotional
states of receivers. It is difficult to examine source effects without
considering the emotional impact of various sources on receivers, since it is
well documented that audience's emotional state can influence message processing
(Lang, Dhillon, & Dong, 1995; Lang, Newhagen, & Reeves, 1996) as well as person
perception and other social judgments (Clark, Milberg, & Erber, 1984; Kernrick &
Cialdini, 1977; Stangor, 1990).
The study reported here explicitly measures the emotional impact of
communication sources on receivers, and examines whether there is a systematic
association between receivers' emotional state and their perception of
communication sources. The emotional state examined in this study is autonomic
arousal, which is one of the two most commonly derived dimensions of emotions
along with the valence dimension (Greenwald, Cook, & Lang, 1989; Lang, Bradley,
& Cuthbert, 1992). Specifically, this study asks the following research
question: For media receivers, controlling for age, sex, majors, and
physiological differences, what is the relationship between communication source
perceptions and electrodermal skin conductance responses (SCRs)?
Communication Sources and Electrodermal Activity
Viewed from a cognitive perspective, the source of communication is one of the
most significant and important stimuli, because human face is such an important
object in the visual world. "Not only does it establish a person's identity,
but also, through its paramount role in communication, it commands our almost
continuous attention" (Ellis, 1981, p. 1). As we all know, most of the
information in the mass media, be it informational or entertaining, is delivered
by one or more communication sources. Prior research has shown that receivers
experience changes in emotional or affective states when they encounter various
communicators. For example, we feel changes in arousal level at the time of
viewing the sources, which in turn may affect such important cognitive processes
as attention and memory (Shepherd & Ellis, 1973). Whether we have an innate
attraction for a certain type of source or we have prior association of certain
sources with important emotional events, communication sources are arousing
stimuli (Shearer & Mikulka, 1996).
Electrodermal activity is a commonly used index of attention, effort, and
arousal (Bernstein, 1973; Maltzman, 1979). It is also a component of the
orienting response (OR) to surprising and significant stimuli (O'Gorman, 1979).
With regard to OR, there is substantial evidence that the SCR component of OR is
reliably elicited by stimuli which have "signal value," or significance, for the
organism (Maltzman, 1979; Tranel, Fowles, & Damasio, 1985).
Communication researchers have used several different physiological measures,
including SCRs, to explore viewer's orienting responses to such structural
features of television as subjective camera movement (Lombard, Reich,
Campanella, & Ditton, 1995), cuts, movements, and onset of commercial messages
(Reeves et al., 1985; Lang, 1990). Viewed from a psychological point of view,
all these structural features of television are significant stimuli, which tend
to draw immediate attention and evoke arousal from the television audience. By
the same token, we might expect that communication sources would be significant
enough stimuli to elicit different levels of arousal in receivers.
The purpose of the current investigation is to explore the relationship between
source perceptions and receiver's autonomic electrodermal responses to sources
from the perspective of the facial recognition model in cognitive psychology.
Considerable evidence in facial recognition studies indicates that different
communication sources may elicit different levels of physiological responses.
Toward this end, this paper will first introduce the facial recognition theory,
review the relevant literature on this topic, and propose a set of hypotheses.
It will then present the methods and results of an experiment conducted to test
those hypotheses. Finally, it will discuss the findings in their appropriate
theoretical and methodological context.
A Multistage Sequential Model of Face Recognition
Several models of face processing have been developed in information-processing
terms (e.g., Bauer, 1986; Bauer & Verfaellie, 1998; Bruce, 1991; Ellis, 1986).
In general, these cognitive models posit that human face recognition is a
function of a series of cognitive processes. In this multistage, sequential
processing model, the initial stage is the perceptual analysis of the faces,
which involves the parallel extraction of featural and configural information
(Bauer & Verfaellie, 1988). It is then followed by a judgment of whether the
face is familiar, and if the face is familiar, a subsequent search for
"identity-specific information." This identification of a previously familiar
face requires additional post-perceptual steps in which a memory representation
of the face is activated because it matches the incoming perceptual information
in some significant way. For example, Bruce and Young (1986) suggest that we
develop an "identity-specific semantic code" from our previous experience with a
person. Included in this code is information about the person's appearance,
demeanor, occupation, family background, hobbies, personality, etc. The
schematic information contained in this code can be activated when we recognize
the person's face or hear the person's voice and information concerning the
person. From a cognitive perspective, according to Bauer & Verfaellie (1988),
"the familiar-unfamiliar face distinction" reflects "presence or absence of
stored identity-specific information about viewed faces." (p. 241)
Past research has shown support for the idea behind the sequential model of
facial recognition. For instance, Tranel, Fowles, and Damasio (1985) found
that when presented with a series of faces of celebrities, politicians, and
newsmakers drawn from current magazines, college students showed greater SCRs to
familiar faces than unfamiliar faces. They also found that familiar faces were
rated by subjects as more "significant" than unfamiliar faces, suggesting that
highly familiar faces are potentially arousing stimuli (Tranel et al., 1985, p.
403).
Bauer and Verfaellie (1988) also found in an experiment of psychophysiological
responses of prosopagnosics[1]1 during facial identification tasks that a
patient with this disease showed relatively larger electrodermal responses to
the names of familiar faces compared to unfamiliar faces.
More recently, Shearer and Mikulka (1996) reported an increase in SCRs as a
function of familiar faces. However, the SCR occurred only when coupled with
the identification task, indicating that the retrieval of the identity-specific
information about faces is an important determinant of face recognition. The
result was interpreted by the authors to suggest that such names activate stored
identity-specific information in memory. If the face conveys any associated
contextual information from past experience, it will carry greater attentional
potentials, which subsequently will result in emotional experiences as
manifested in greater arousal, greater SCRs in particular. Conversely, if the
face is not familiar and does not carry any contextual information for the
viewer, then the sequential process will stop right after the initial stage,
since there is no need or utility for any further searches. This tendency will
be manifested in lesser arousal or lesser SCRs. The same reasoning can be
applied to the recognition of communication sources. If a source is perceived
by the viewer to be significant, there will be a subsequent search for
identity-specific information, which includes associated contextual information
from past experiences. This sequential process will be displayed by greater
SCRs for the viewer. It is also documented that people tend to display
significantly greater SCRs to cognitively consistent visual stimuli D scenes
related to their preferred interests or recreation (Matzman & Boyd, 1984).
Although not discussed in a greater detail in this paper, cognitive theories
also suggest that people are attracted to others who share similar attitudes,
values, and beliefs in order to maintain balance or consistency in their
cognitive states (Festinger, 1957; Newcomb, 1961).
In sum, prior theory and research suggest an electrodermal discrimination of
significant versus non significant communication sources. In fact, not all
media sources have the same "signal value" or "stimulus significance" to
viewers. Some media sources may be more significant partly because they are
perceived by viewers to be more familiar or relevant than others. Likewise,
media sources from different program genres are also likely to display different
levels of "stimulus significance" to viewers, because the genres provide
additional contextual information beyond mere facial recognition.
Hypotheses
Based on the previous discussion of research and theory concerning facial
recognition, two general hypotheses concerning the effects of communication
sources on the SCR were proposed.
H1a: Different communication sources will elicit different levels of
skin conductance responses (SCRs).
H1b: Communication sources identified with different genres of TV
programs will elicit different levels of skin conductance responses
(SCRs).
While the first hypothesis examines electrodermal correlates of particular
sources, the second hypothesis is related to those of particular classes of
media sources. The reasoning behind it is that people experience different
emotions toward particular classes of media sources. Intuitively, we might
guess that entertainment sources will provide viewers with more emotionally
associated contextual information than other classes of sources such as
newsmakers or politicians, or vice versa depending on individuals' past
experiences with them.
One of the consistent findings in facial recognition research is that
familiar faces elicit greater SCRs than unfamiliar faces. Familiar faces such
as well-known public figures elicit much larger SCRs and are rated as more
significant than the unfamiliar faces among college students (Tranel, et al.,
1985). This is also true for individuals with an inability to recognize faces
who are still able to show the orienting response to familiar faces (Bauer &
Verfaellie (1988). Thus:
H2: Familiar sources as compared to less familiar sources will elicit
greater arousal (SCRs).
We are attracted to communication sources we like; the more we like a source,
the more we will be persuaded by him or her (McGuire, 1969). We are also
attracted to sources who are rewarding than those who are not rewarding
(Birnbaum & Stegner, 1979). In this sense, those likable sources, per se, are
significant stimuli from which we all experience various emotions when we
encounter them.
Bio-informational theory of emotion posits that the action dispositions and
their physiological manifestations are linked to nodes in the brain that
represent attributes of the emotion-eliciting stimuli (Lang, 1995). The key to
this approach is to investigate the specific attributes of stimuli; that is,
those characteristics that become nodes in the emotion network (Detenber &
Reeves, 1996). Clearly, communication sources who are likable and physically
attractive are primitive heuristics that, in many instances, influence our
judgments and emotional responses by virtue of their associations with specific
information and emotions in the brain. For instance, we feel happy when we
encounter media sources we like, because it is automatically activated by a
simple linkage between those images and feelings. Likewise, we feel the same
happiness when we encounter a media source who is physically attractive. This
coactivation is the reason why we feel rewarded whenever we see physically
attractive models in commercials, even though they have nothing to do with the
message provided. Evidence showing the physiological effects of communicator
attractiveness and likability is scarce. However, recent research findings
indicate that likable and attractive sources may elicit greater arousal. For
instance, Cuthbert et al. (1996) found that when presented with pictures
depicting a variety of events, subjects displayed greater arousal to
positively-valenced pictures than neutral pictures. By the same token, we can
expect that both attractive and likable sources would elicit pleasant feelings
in subjects. These happy or positive feelings would be manifested in greater
SCRs. Accordingly, it was expected:
H3: The more likable a source, the greater the arousal (SCRs).
H4: The more attractive a source, the greater the arousal (SCRs).
Method
A within-subjects experiment was conducted to test these hypotheses. The
independent variable was manipulated by showing pictures of 22 different
communication sources to subjects. The primary dependent variable was
electrodermal activity, as measured by the skin conductance responses (SCRs).
In addition to SCR measures, subjects were instructed to evaluate their
perceptions of each communication source on a paper-and-pencil questionnaire.
Subjects
Twenty-eight undergraduate and graduate students (12 men, 16 women) enrolled in
communication classes participated in the study in exchange for course credits.
The experiment was administered to subjects one at a time. All subjects signed
an informed consent form before commencing the experiment.
Stimuli
The stimuli were a total of 22 facial images of newsmakers (e.g., Dan Rather,
Tom Brokaw, Joie Chen, Peter Jennings), game show hosts (e.g., Alex Trebek),
entertainment hosts (e.g., David Letterman, Jay Leno), and celebrities (e.g.,
first lady). Two additional slides were shown to serve as practice sources.
All stimulus materials were drawn from actual television broadcasts. For
newsmakers, both local and national newscasters were randomly selected. To
minimize order effects, four orders of picture presentation were constructed so
that, across subjects, the same picture was seen in different positions in each
presentation.
Apparatus
All the images were presented on a screen placed approximately 3 m in front of
the subjects. A pair of Silver-Silver Chloride AgAgCl electrodes with Velcro
straps was used to measure SCRs. All electrodermal activities were digitally
recorded in units of electrical conductance using a Biopac MP30 hardware unit
and associated psychophysiology software.
General Procedure
Upon arriving at the laboratory, subjects were instructed to wash their hands
using Ivory hand soap. All subjects were asked to sign the informed consent
form before commencing the experiment. Electrodes were attached to the palmar
surfaces of the distal phalanges of the middle and index fingers of the
subject's non-dominant hand using Velcro straps. Electrodes were filled with a
saline electrode paste recommended by Fowles et al. (1981). Each subject was
seated in a comfortable chair and instructed to relax. After a first 15-min.
baseline period during which the instructions were read, each subject was shown
two practice sources to allow for adjustment to the experimental procedure and
to minimize electrodermal reactivity (Shearer & Mikulka, 1996). After the
practice sources, the 22 source images were presented in one of four different
orders.
The subject was instructed that a series of pictures would be presented and
that each slide would be presented for approximately 6 s, followed by nothing
but the blank screen.[2]2 After watching the sources for 6 s, the subject was
instructed to fill out a questionnaire regarding their impressions of the source
they had just seen. The subject was presented the next source with randomly
determined intersource interval that varied from 5 to 10 s. The subject
repeated this procedure for all twenty two sources, and was thanked after the
last source.
Measures of Source Perceptions
The subject rated each source for familiarity, believability, likability,
intelligence, and attractiveness on a scale ranging from 1 (not at all) to 9
(very much). These are the characteristics commonly used in previous source
effects studies.
To measure impressions of the source, the subject was asked, "How does this
person seem?" The nine semantic differential items, used in prior research on
personality research ( e.g., Burgoon & Walter, 1990) and television screen size
effects (Lombard, 1995), were good/bad, warm/cold, confidence/insecure,
sensitive/insensitive, not intimidating/intimidating, friendly/unfriendly,
strong/weak, attractive/unattractive, and similar to me/different from me.
Also measured was subject's emotional responses to sources by asking, "How does
this person make you feel?" Six bipolar semantic differential items with a
9-point scale were calm/anxious, good/bad, confidence/insecure, safe/threatened,
comfortable/uncomfortable, and sociable/unsociable. These items again were
derived from previous research on interpersonal distance, personal space, and
screen size effects studies (e.g., Burgoon, 1978; Lombard, 1995).
Skin Conductance Responses (SCRs)
Based on the different measurement techniques suggested by researchers (e.g.,
Lang, 1995), audience's state of arousal was assessed via electrodermal skin
conductance responses (SCRs). SCRs, the primary dependent variable in this
study, was quantified in such a way that for each source presentation, a latency
window of from 1-5s from stimulus onset was used, and the amplitude of the
largest SCR with onset falling within this window was recorded (Cuthbert, et al,
1996; Tranel, et al, 1985). A log transformation (log(SCR+1)) was performed to
normalize the distribution (Cuthbert et al., 1996).
Data Analysis
The primary statistical procedure used to test the hypotheses was a one-way
repeated-measures analysis of variance (ANOVA) for H1a and H1b. To examine H2,
H3, and H4, regression analyses were used. In addition to the main hypothesis
tests, some exploratory results are also reported.
Results
Hypothesis 1a predicted that different communication sources will elicit
different levels of skin conductance responses (SCRs). Analysis of the primary
dependent variable of subjects' SCRs to the different sources yielded a
statistically significant effect, F(21, 567) = 2.56, p < .01, which indicated
that some communication sources elicited greater electrodermal response
amplitudes than other sources. Hence, H1a was supported.
Hypothesis 1b predicted that different types of communication sources will
elicit different levels of skin conductance responses (SCRs). To test this
hypothesis, twenty one sources were categorized into four different types:
entertainment, local news, national news, tabloid. One source (first lady) was
excluded from the analysis because she was the only source in the category.
Results from the one-way analysis of variance (ANOVA) on the primary dependent
variable showed a significant mean differentiation as a function of the types
of source, F(3, 557 ) = 3.44, p < .01, indicating that hypothesis 1b is
supported (see Figure 1). Figure 1 shows that entertainment sources (M = .235)
elicited the greatest SCRs, while tabloid sources (M = .14) elicited the least
SCRs.
Hypothesis 2 predicted that source familiarity is positively correlated with
level of arousal (SCRs). The results of the regression analyses between source
familiarity and the SCRs showed a significant relationship, F(1, 614) = 29.69, p
< .001. The fit model showed source familiarity was a significant predictor of
SCRs (Beta = .016, p < .001). The results indicate that as the source
familiarity increases, the SCRs also increase. Therefore, Hypothesis 2 was also
supported.
Hypothesis 3 predicted that source likability will elicit greater arousal
(SCRs). The results of the regression analyses supported the
hypothesis, F(1, 614) = 5.78, p < .01. Likability, too was a significant
predictor of SCR (Beta =.011, p < .01).
___________________
Insert Figure 1 About Here
___________________
Hypothesis 4 predicted that more attractive sources will elicit greater arousal
(SCRs) than less attractive sources. Results from the regression analyses
showed that this is not the case, F(1, 614) = .30, n.s.). Therefore, H4 was not
supported.
Exploratory Data Analysis
To further examine the relationship between communication source
characteristics and viewer responses, data from several additional questionnaire
items were analyzed. An one-way analysis of variance demonstrated significant
gender differences in the SCRs. For example, across the entire set of sources,
male subjects (M = .21), compared to female subjects (M = .15), displayed
significantly greater average SCRs, F(1, 614) = 8.511, p < .003. Gender of
sources also made a difference. Male sources (M = .19), compared to female
sources (M = .14), elicited greater arousal from the subjects, F(1, 614) = 5.22,
p < .02.
The fourteen items related to source perception were subjected to factor
analyses. A principal-components analysis with varimax rotation generated three
factors of source characteristics : "warmth," "credibility," and
"attractiveness." Together, they accounted for 67.5 percent of the variance.
Items loading on each factor were summed to create indices. To examine whether
different types of media sources impact these composite factors, source types
were subject to analyses of variance with the three indices as dependent
variables.
___________________
Insert Figure 2 About Here
___________________
Only one factor, "credibility," showed a significant difference as a function
of source type, F(3, 587) = 24.37, p < .01 (see Figure 2). Tabloid news sources
suffered most on credibility, while other types of communication sources were
about equal credibility. Interestingly, entertainment sources were perceived by
subjects to be more credible communication sources than newsmakers, although
post-hoc analyses showed the difference to be statistically insignificant.
Discussion
This study attempts to explain how different characteristics of communication
sources affect television viewers' physiological responses. Toward this end, a
sequential model of source perception was introduced from the facial recognition
theories in cognitive social psychology.
According to this model, viewers first judge whether a particular source they
encounter is a significant or familiar face, and if the source is judged to be
significant, a more thorough search is conducted, which includes naming of the
source or associated contextual information. Although the data presented in
this paper were not intended to articulate the nature of the processes
underlying the source perception, the empirical evidence of increased skin
conductance responses (SCRs) after the onset of stimuli indicates the presence
of these cognitive efforts amongst receivers.
The results of this study provided additional evidence for the multistage model
of face recognition. It was found that different communication sources elicited
different levels of emotional responses from subjects. Some media sources were
able to elicit greater emotional responses than other sources as manifested by
the increased SCRs. Further analyses of the data demonstrated that familiar
sources were more likely than less familiar sources to elicit greater responses
for the subjects. A reasonable conclusion is that familiar communication
sources, like other structural features of television stimuli, bear "signal
value," or significance for the organism (Bernstein & Taylor, 1979; Tranel et
al., 1985).
Another important finding in this study is that source type also made
differences in eliciting physiological responses. This supports the notion of
"identity-specific semantic code" (Bruce & Young, 1986) whereby we factor in our
prior experiences as well as related contextual information in our responses to
communication sources. It was found that subjects displayed the greatest SCR
response to entertainment sources (M = .235) and the least response to tabloid
sources (M = .14). One possible explanation for this difference might be that
entertainment sources are more familiar than tabloid sources. An exploratory
analysis showed a huge difference in the familiarity measure between these two
types of sources. The average score for entertainment sources on a 9-point
scale was 8.35, while that for tabloid sources was 4.08. Although they were
different in other dimensions, it was a single familiarity measure which
discriminated the two most successfully. This implies that the two sources
possess different "signal values" or significance for the viewers.
Another result that deserves further discussion is that source attractiveness
did not have significant effects on physiological responses. Given the
empirical evidence that physical attractiveness of the model or spokesperson is
an important variable which interacts with the product advertised to affect the
viewers and readers' response to the advertisement (Baker & Churchill, 1977), it
was hypothesized that more attractive sources must elicit greater viewer
attention and emotional responses. But this was not the case in this study.
One possible explanation is that the attractiveness item used in this study
might have been overly broad. It might have meant physical attractiveness for
some people and general attractiveness for others. Lack of clarity in the
measure might have contributed to the null effect.
Viewed from the sequential model of facial recognition, null effects simply
suggest that source attractiveness does not motivate viewers for a further
search. In other words, the minimal responses after the onset of the stimuli
for attractive sources might mean that the subjects terminated any further
searches for that particular source. Unlike commercials in which stakes are high
for the viewers, the present experiment required minimal involvement from
subjects. For that reason, they didn't have to pay extra attention to the
sources they didn't know much, even if they were attractive sources. And it is
important to notice that all the source images used in this study were somehow
public figures and may not have the arousal value of personal acquaintances.
In sum, the present study provided an important conclusion about source
effects: there appear to be some physiological correlates of communication
sources. Familiar sources are potential "signal stimuli," like other structural
features of television. This finding is valid across different classes of
communication sources. Besides supporting theorized claims about face
recognition, the experiment's findings have practical implications for the
industry. The study provides a physiological basis for classifying media
sources along receiver-based criteria such as "signal value."
While the evidence provided here can be supportive of the model in facial
recognition literature and help our understanding of source effects, future
research could identify other physiological correlates of communication sources.
The experiment could be replicated for other communication sources not examined
in this study. To increase the generalizability of the study, future
experiments could benefit from a larger sample of sources.
A limitation of the present study is that all the subjects were students
enrolled in various communication classes. Certainly, the subjects participated
in this study, compared to students from other disciplines, might have more
experiences with various news sources. This limits the external validity of the
study. Future studies may benefit by using non-communication students as well
as non-student subjects.
Future research could also explore the detailed processes underlying these
effects, and what these effects have to do with other aspects of information
processing of communication messages, such as memory and retrieval. Researchers
have demonstrated that the arousal dimension of emotion had a stable effect on
memory performance. Pictures rated as highly arousing were remembered better
than low-arousal stimuli (Bradley, et at., 1992). Applying their findings to
the results of this experiment, we may conclude that messages delivered by some
communication sources will be better remembered than those delivered by other
sources.
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Figure Caption
Figure 1. Amplitude of mean skin conductance responses as a function of
different source types: Entertainment (M = .235), Local News (M = .171),
National News (M = .160), and Tabloid (M = .14). SCR was measured in
microsiemens.
Figure Caption
Figure 2. Mean differences on credibility as a function of source types.
Credibility is a composite of Familiarity, Believability, Likability,
Intelligence, Confidence, and Strong-ness.
[1] Notes
1 Prosopagnosia is a syndrome in which a patient with brain damage becomes
unable to recognize previously familiar persons by visual references to their
facial features. The patient recognizes faces as faces, but cannot determine
specific facial identity.
[2] 2 Six seconds proved to be a practical length for selecting single shots of
a wide variety of content (Cuthbert et al., 1996; Detenber & Reeves, 1996).
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