Chapter 2
EMOTIONAL DIMENSIONS
Chapter 2
EMOTIONAL DIMENSIONS
2.1
Emotional process
The emotional process, like any other cognition process, is complex and requires
multiple steps. The first step is activation or arousal. Activation is followed by evaluation
of the situation. For example, whether a given situation poses a threat or no threat, as well
as whether one is facing a prey or a predator. Based on the assessment, either the
inhibitory or energizing process is activated and then appropriate emotional behaviours
are expressed. Each stage of the emotional process is associated with physiologic
changes.
a) Activating mechanisms. Activation, a core concept in emotions, is defined as
readiness for emotional behaviour.
b) Evaluation functions. The evaluating system of animals, which can work with or
without cognitive awareness (presuming that only humans have cognitive awareness),
works in three stages:
1) assesses events for their relevance,
2) directs action in response, and
3) feeds information to the hypothalamus (the head ganglion of the autonomic system)
to regulate physiologic response.
For example, an animal assesses the size and strength of another animal, and
determines whether the response should be aggression or withdrawal. In terms of
emotions, evaluation functions help to distinguish whether the emotion is positive or
negative.
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Based on these aspects of the emotional mechanism, the idea of representing
emotions as a multidimensional space arises.
2.2
Dimensionality of emotions
Emotion dimensionality is a simplified description of basic properties of emotional
states. According to Osgood, Suci and Tannenbaum’s theory [Osg57] and subsequent
psychological research (s. [Dat64, Meh74])], the communication of affect is
conceptualised as three-dimensional with three major dimensions of connotative meaning,
arousal, pleasure and power. The three different dimensions are regularly mentioned in
the literature related to emotion analysis and are defined as follows:
 Activation or Arousal: Refers to the degree of intensity of the affect and ranges
“from sleep to frantic excitement” [Pit93]. It is also related to the degree of readiness to
act. Research from Darwin on has recognised that emotional states involve dispositions to
act in certain ways. A basic way of reflecting that theme turns out to be surprisingly
useful. States are simply rated in terms of the associated activation level, i.e. the strength
of the person’s disposition to take some action rather than none. Activation dimension
differentiates, for instance, anger from boredom. While the first one possess a high
activation level, the last one presents lower disposition to act, and therefore lower
activation level.
 Evaluation or Valence: Determines how positive or negative, liking or disliking
the affect is. This dimension reflects the clearest common element of emotional states; an
individual is materially influenced by feelings that are ‘valenced’, i.e. they are centrally
concerned with positive or negative evaluations of people or things or events. The link
between emotion and valence is widely agreed, although authors describe it in different
terms. Arnold refers to the ‘judgement of weal or woe’; Tomkins, describes affect as what
gives things value - ‘without its amplification, nothing else matters, and with its
amplification, anything else can matter’; Rolls sees emotional processing as where
"reward or punishment value is made explicit in the representation". For instance, happy
is considered to be positive, i.e. it has a high evaluation level, while angry presents a
negative value, i.e. low evaluation level.
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 Power or Control: Relates to the degree of power or sense of control over the
affect, and helps distinguish emotions initiated by the subject from those elicited by the
environment e.g. contempt versus fear. It is also related to the degree of
dominance/submission.
The main advantage of this theory is that it provides taxonomy allowing simple
distance measures between emotion categories, as well as a continuous framework for
expressing gradual, non-extreme emotional states. However, three dimensions do not still
capture all the relevant aspects of an emotional state.
2.3 Theory of the activation – evaluation space
Activation-evaluation space is a particularization of the dimensionality introduced in
section 2.2, which results in a representation that is both simple and capable of capturing
a wide range of significant issues in emotion. It rests on a simplified treatment of two key
themes: pleasure (evaluation) and arousal (activation).
Figure 2.1. Graphic representation of the activation-evaluation theory of emotions.
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The axes of activation-evaluation plane reflect those themes. The vertical axis shows
activation level, the horizontal axis evaluation. A basic attraction of that arrangement is
that it provides a way of describing emotional states which is more tractable than using
words, but which can be translated into and out of verbal descriptions. Translation is
possible because emotion-related words can be understood, at least to a first
approximation, as referring to positions in activation-emotion space. Various techniques
lead to that conclusion, including factor analysis, direct scaling, and others.
Activation-evaluation space is a surprisingly powerful device, and it has been
increasingly used in computationally oriented research (s. [Sca97, Cow99a, Cow99b]).
However, it has to be emphasised that representations of that kind depend on collapsing
the structured, high-dimensional space of possible emotional states into a homogeneous
space of two dimensions. There is inevitably loss of information; and worse still, different
ways of making the collapse lead to substantially different results.
Research suggests that the activation-evaluation space is naturally circular, i.e. states
that are at the limit of emotional intensity define a circumference. The states that are the
limit of emotional intensity are equidistant from an emotional neutral point (see figure
2.1). Many techniques converge on the conclusion that to a first approximation, emotion
terms can be understood as referring to points in a space defined by those two axes.
[Per00] performed an experiment based on listening tests of some emotional
utterances (cold anger, hot anger, happiness, neutrality and sadness). Results concluded
that all the emotions were significantly different from each other on at least two of the
dimensions. Findings in [Per00] show that the concept of the dimensions of emotion is
useful to describe and distinguish emotions; and that emotions with a similar level of
arousal, and sometimes a similar level of power, share acoustic characteristics in terms of
F0 range and mean, and particularly intensity mean. It is also suggested that this
contributes to perceived similarity between emotions, and consequently confusions,
especially in hearing-impaired. It was observed that, in the majority of the cases, the two
emotions confused were closer on the arousal dimension than on the other two
dimensions.
In the framework of the PHYSTA project a system called FEELTRACE [Cow00] is
designed to represent emotions on the activation-evaluation plane. The function of this
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tool is to record the way the signs are perceived by representative observers through a
system that they find easy to use, and that gives reasonably reliable outcomes. Results of
the test of FEELTRACE are consistent with the theoretical approach.
2.4
Assumption of the present work
Most of the prior work on emotion recognition [Bat00, Hub98]) makes only use of
acoustic prosodic features, due to their ease of handling, which give mainly information
concerning the arousal dimension of emotions. This study deals with a second dimension
of the emotional space, i.e. pleasure, and its relation to quality features, i.e. auditory
features that arise from variation in the source signal and vocal tract properties (see
section 3.3). For instance, happiness and anger are emotions expressed with high
intensity, i.e. with a high level in the arousal dimension, which makes them very difficult
to classify based uniquely on prosodic features. However, they are situated opposite to
each other on the pleasure axis, and therefore, quality features will contribute effectively
to enhance this classification.
The assumption of this work is that both dimensions of the emotional space relate to
different features of the speech, with different degrees of complexity [Tat02]. Therefore,
it makes sense to divide the problem and apply hierarchical classification accomplished in
terms of levels, from high to low, looking at a subspace of the features (prosodic or
quality features).
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