Positive and Negative Emotional Dichotomy
Jorge Teixeira
Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, Porto, Portugal
Vasco Vinhas, Eugenio Oliveira, Luis Paulo Reis
Faculdade de Engenharia da Universidade do Porto, Rua Dr. Roberto Frias s/n, Porto, Portugal
LIACC - Artificial Intelligence and Computer Science Laboratory, Rua Campo Alegre 823, Porto, Portugal
Medical Signal Acquisition, Data Analysis and Processing, Emotion Assessment, Electroencephalography,
Galvanic Skin Response.
While affective computing and the entertainment industry still maintain a substantial gap between themselves,
biosignals are subject of digital acquisition through low budget technologic solutions at neglectable invasive
levels preventing users from focusing their awareness in the equipment. The integration of electroencephalog-
raphy, galvanic skin response and oximeter in a multichannel framework constitutes an effort in the path to
identify emotional states via biosignals expression. In order to induce and detect specific emotions, gender
specific sessions were defined based on the International Affective Picture System and performed in a con-
trolled environment. Results granted by distinct analysis techniques showed that high frequency EEG waves
are strongly related to emotions and are a solid ground to perform accurate emotion classification. They have
also given strong indications that females are more sensitive to emotion induction. On the other hand, one
might conclude that the attained success levels concerning relating emotions to biosignals are extremely en-
couraging not only to the continuation of this research topic but also to the application of these results in
domains such as multimedia entertainment, advertising and medical treatments.
Affective computing is consistently becoming a con-
firmed scientific domain with practical applications
while the entertainment industry as a whole, and spe-
cially the cinematographic and videogame branches,
which have been closing the semantic gap between
them, constitute an economic giant. Having this
macrocontextualization in mind, the authors have al-
ready engaged a research project with the main inten-
tion of using emotion assessment through biosignals
to promote both subconscious interaction and individ-
ual specific appropriated content delivery.
The presented study finds itself integrated in this
scope, as it perfectly falls in the emotion assessment
research module. The proposed system constitutes a
solid technologic framework that intends to enable bi-
ological information acquisition in a controlled en-
vironment having as initial hypothesis the existence
of human physical expression of emotional states that
can be objectively measured by relatively inexpensive
equipment. The multichannel structure was defined
by exploiting known techniques, namely electroen-
cephalography, galvanic skin response and heart rate
monitoring, and emotional states were induced using
third-party catalogued pictures.
The first goal was to effectively define, build and
test an experimental session framework where sub-
jects followed a given strict protocol in order to vi-
sualize and/or interact with multimedia content. This
framework was designed not only to collect data but
also to constitute a validation environment. The sec-
ond objective was to, using the given platform, iden-
tify specific, controlled and extractable biological sig-
nals that could be used as emotion index factors ap-
plied to all subjects or to a characteristic group of
The confirmation of the initial hypothesis and
project goals would enable its immediate application
in developing a full or semi-automatic emotion clas-
sification engine that would be able to apply and use
the identified signal patterns to, in real-time, identify
Teixeira J., Vinhas V., Oliveira E. and Paulo Reis L. (2008).
MULTICHANNEL EMOTION ASSESSMENT FRAMEWORK - Positive and Negative Emotional Dichotomy.
In Proceedings of the Fifth International Conference on Informatics in Control, Automation and Robotics - SPSMC, pages 249-252
DOI: 10.5220/0001486902490252
the subject’s emotional states with high accuracy.
In order to better detail the presented study, this
document is structured as follows: the domain state of
the art is described in the next section, in section 3 the
multichannel emotion assessment framework is pre-
sented with special emphasis in the most significant
decisions. Still in that section, results are presented
and related conclusions are extracted in section 4 as
well as are identified future work areas and practical
domains of application are suggested.
The emotional state of human beings belongs to a
complex theme since its definition is not unique and
its essence not consensual. An overview of the emo-
tion assessment is presented in the next subsection, as
well as a brief description of the most common ap-
proaches to emotional induction, and finally a refer-
ence to equipment solutions.
2.1 Emotion Assessment
The emotion itself can be seen as a consequence of
an action or an environment cause so that the induc-
tion of a specific emotional state is tightly connected
with an arousal procedure. In order to identify and
assess an emotion, patterns are used and they con-
stitute different approaches to the emotional induc-
tion, which will be discussed in the next subsection.
Apart from the induction, the classification is essen-
tial, and can be accomplished based on a coincidence
of values on a strategic number of dimensions (Lo-
gothetis, 1957). Based on this study, the emotion as-
sessment can be analyzed through three distinct di-
mensions. The two primary levels are the valence
and the arousal, and the secondary one is the domi-
nance, which has a weaker relationship with the oth-
ers (P.J. Lang, 2005)(A. Mehrabian, 1974).
In order to best analyze the assessment of the pic-
tures, it is generally used an affective space. This is a
standardized method to graphically display the emo-
tional assessment results of the pictures. According
to the valence and arousal mean values, it is plotted
a bidimensional graph where the horizontal-axis rep-
resents the arousal and the vertical-axis the valence,
both scaled from 1 to 9.
2.2 Generic Approach to Emotion
There is not a process for emotional induction that is
perfectly suitable for all cases, but a group of different
approaches to achieve the same objective. A prevalent
method to induce emotional processes consists of ask-
ing an actor to feel or express a particular mood. This
strategy has been widely used for emotion assessment
from facial expressions and to some extent from phys-
iological signals (G. Chanel, 2005). However, even
for expert actors for whom the capacity to achieve a
specific emotional state is obvious, it is hard to guar-
antee that the physiological responses are consistent
and reproducible by other non-actor people.
An alternative approach to the emotional induc-
tion is composed by multimedia stimuli. Music, im-
ages, videos and video-gamesbelongsto a category of
stimuli that has significant advantages compared with
the induction through actors, since there is no need
of actors and the quality of the induced emotions is
greater as they are more realistic.
2.3 Equipment Solutions
Emotions’ assessment needs reliable and accurate
communications with the subject so that the results
are conclusive and the emotions correctly classified.
This communication can occur through several chan-
nels and is supported by specific equipment. The BCI
- Brain Computer Interface - is directly connected
to this area and uses two different approaches, inva-
sive and non-invasive methods. The invasive meth-
ods are clearly more precise, however more danger-
ous and will not be considered for this study. On the
other hand, non invasive methods such as EEG, fMRI,
GSR, oximeter and others have shorten the distance
between the utopia and the truth of understanding the
human brain behaviour, gathering together the advan-
tages of inexpensive equipment and non-medical en-
Due to the medical community skepticism, EEG,
in clinical use, it is considered a gross correlate of
brain activity (Ebersole, 2002). In spite of this reality,
recent medical research studies (Pascalis, 1998)(Af-
tanas, 1997) have been trying to revert this scenario
by suggesting that increased cortical dynamics, up to
a certain level, are probably necessary for emotion
functioning and by relating EEG activity and heart
rate during recall of emotional events. Similar efforts,
but using invasive technology like Electrocorticogra-
phy (ECoG), have enable complex BCI like playing a
videogame or operating a robot (Leuthardt, 2004).
Some more recent studies have successfully
used just EEG information for emotion assessment
(K. Ishino, 2003). These approaches have the great
advantage of being based on non-invasive solutions,
enabling its usage in general population in a non-
medical environment. Encouraged by these results,
ICINCO 2008 - International Conference on Informatics in Control, Automation and Robotics
the current research direction seems to be the addi-
tion of other inexpensive, non-invasive hardware to
the equation. Practical examples of this are the intro-
duction of GSR and oximeters by Takahashi (Taka-
hashi, 2004) and Chanel et al(G. Chanel, 2005).
On this study three non-invasive equipments will
be used in parallel so that the reliability of all the
procedures is guaranteed. A Neurobit Lite EEG de-
vice with one active electrode and two references, a
Thoughtstream biofeedback system Galvanic Skin
Response with two dry electrodes and an oximeter
with a finger sensor.
In this section it will be given a brief overview of
the whole project development.The procedures and
methods involved on this study were grouped into two
parts. The first one deals with the emotional induc-
tion approach used on this study and the last one re-
veals the experimental conditions used along the ex-
perimental sessions.
A good experimental control and an easy, yet ef-
ficient, method for results comparison are key factors
that demand an effective set of visual stimuli. The
IAPS library is so the most indicated emotional in-
duction method, as it has been widely used through
the research community and all the pictures classified
according to valence, arousal and dominance (L. Af-
tanas, 2001)(G. Chanel, 2005)(M. Muller, 1999).
The experimental conditions are an essential is-
sue to the validation and acceptance of the results ob-
A total of twenty eight subjects, seventeen males
and eleven females, all right-handed aged eighteen-
thirty years old took part in this study. All subjects
had access to an introductory text for the experimen-
tal session in order to access the essential information
about the main procedures involved and a question-
naire filled before each session to avoid possible bar-
riers as mental diseases.
The experimental results of this study are based
on a statistical analysis.
This analysis indicates that mens behaviour is dif-
ferent from the womens one, since the mean ampli-
tude of the high frequency brain waves is higher along
the entire experimental session.
Considering the GSR data, it is presented the slope
variation between the three stages - happiness, neutral
and sadness - and analyzed its behaviour along the
complete session.
The heart rate analysis indicates an unexpected
and almost undetectable variation of its value.
In what regards to the first topic, one ought to assert
that the initial study’s main goals were completed un-
dertaken. The described experiments achieved to de-
velop and test a solid framework to conduct controlled
emotionally-evocative experiments enabling flexible
capability of recording and monitoring biosignals in
At a more detailed level, it was possible to define
dynamic gender-designed emotional sessions, with
fine tuning capabilities, in order to trigger specific
emotional states. The data provided from the con-
ducted experiments was input to the detailed sys-
tem’s architecture that provedto be able to supply ses-
sions with biosignals real-time monitoring and stor-
age for physical and temporal independent process-
ing. The achieved results also demonstrated that
the postsession data processing techniques were ef-
ficient and effective in what concerns to emotional
states/biosignals correlation identification.
Having the studys results, presented in the pre-
vious section, as solid ground, it is possible to con-
firm that basic emotional states have biological man-
ifestations capable of being captured and recorded by
the selected equipments, specially with EEG and GSR
Concerning subject variables, it is plausible to
state that females react more aggressively to the pre-
sented pictures, triggering with more expression and
effectiveness the desired emotional states. These ob-
jective data was also corroborated by the interviews
conducted at the end of each sessions, where female
subjects consistently stated that they felt happy and in
a good mood in the first stage of the session and sad
at the end. In the same interviews, a high percent-
age of male subjects affirmed that they did not felt a
deep emotional commitment along the picture presen-
The fact that gender is a key factor in what con-
cerns emotional state triggering through multimedia
content constitutes the first major contribution of the
present study.
Exploiting the evidence that EEG signals were
strongly influenced by the subject’s emotional states,
a more detailed data analysis was performed, as il-
lustrated in the previous section, with special focus
to high frequency signals, namely beta and gamma
waves. The data provided strongly suggests that,
specially in female subjects, high frequency relative
MULTICHANNEL EMOTION ASSESSMENT FRAMEWORK - Positive and Negative Emotional Dichotomy
EEG values are directly correlated to valence, inde-
pendently of their initial standard level. The data pro-
vided suggests that beta and gamma waves strongly
seam to vary directly with valence, enabling, indi-
rectly and with conjugation with other inputs, emo-
tional state detection.
Despite the described positive outcome, there
were identified some features that, although did not
match the initial assumptions, have already been sub-
ject of turnaround strategy definition. The first one
is related to the inexistence of generic significative
changes in heart rate values along experimental ses-
sions and the second resides in the fact that the ex-
pected GSR readings curve high conductivity with
high arousal situations was not recorded as often
as predicted. The authors believe that the existence
of these issues is grounded on the fact that the de-
signed emotionally-evocative sessions based only on
pictures do not trigger such strong emotions capable
of significantly influence biosignals such as heart rate.
It is believed that it would be necessary much strong
multimedia content provided in a more immersive en-
vironment so that subjects could be more deeply in-
4.1 Future Work
The main future work topics are not only related to
this particular study, once it is a spin off/module of a
major one, but also with the main global project. With
this in mind, there were identified the following areas:
More Sophisticated Equipment Reinforcement: It
is intended to acquire more sophisticated equip-
ment, specially and specifically in what concerns
to a multi-channel EEG and a more sensible and
reliable GSR;
Equipment Diversity: It would be useful to inte-
grate in the developed framework new equipments
capable of reading and extract more biosignals,
namely pupil dilatation, voice analysis and facial
expression recognition;
More Detailed Emotion Classification: using the
depicted key factors with conjugation with others
provided by the study continuation and data vol-
ume and diversity enhancement brought, by new
equipment acquisition, it would be plausible to
perform automatic subject emotion classification
with deeper detail levels.
Software Control: The accomplishment of the
previous items would enable both conscious and
subconscious control of several tools and/or mul-
timedia contents;
Considering the studied problem as a whole, specif-
ically the emotion classification topic, several practi-
cal domain applications are not only feasible but also
attractive. Most of the immediate technology adapta-
tions shall reside in the entertainment industry, both in
audiovisual and videogame branches through multi-
media content adaptability to user’s emotional states.
Other possible application areas are user interface en-
hancement, direct advertising and medical applica-
tions, namely in phobia treatments and psychological
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