Overlapping Speech, Utterance Duration and
Affective Content in HHI and HCI – an Comparison
Ingo Siegert, Ronald B
¨
ock, Andreas Wendemuth
Cognitive Systems Group
Otto von Guericke University Magdeburg, Germany
{firstname.lastname}@ovgu.de
Bogdan Vlasenko
Idiap Research Institute
Martigny, Switzerland
bogdan.vlasenko@idiap.ch
Kerstin Ohnemus
davero Dialog Gruppe
91058 Erlangen, Germany
kerstin.ohnemus@davero.de
Abstract—In human conversation, turn-taking is a critical
issue. Especially if only the speech channel is available (e.g.
telephone), correct timing as well as affective and verbal signals
are required. In cases of failure, overlapping speech may occur
which is in the focus of this paper. We investigate the davero
corpus a large naturalistic spoken corpus of real callcenter
telephone conversations and compare our findings to results on
the well-known SmartKom corpus consisting of human-computer
interaction. We first show that overlapping speech occurs in
different types of situational settings – extending the well-known
categories cooperative and competitive overlaps –, all of which
are frequent enough to be analyzed. Furthermore, we present
connections between the occurrence of overlapping speech and
the length of the previous utterance, and show that overlapping
speech occurs at dialog instances where certain affective states are
changing. Our results allow the prediction of forthcoming threat
of overlapping speech, and hence preventive measures, especially
in professional environments like call-centers with human or
automatic agents.
I. INTRODUCTION
Human communication consists of several information
layers, of which the factual layer is the most important. But
beyond the pure textual information other relevant information
such as affective state, self-revelation, and appeal are transmit-
ted [1]. These different pieces of information are provided to
support human conversations and to increase the likelihood of
a fluent conversation.
One important requirement for a fluent and successful
conversation is an efficient turn-taking, which has to be orga-
nized by specific “underlying mechanisms”, such as intonation,
semantic cues, facial expressions, eye contact, breathing, and
gestures [2], [3], [4]. In the organization of turn-taking and
to evaluate the conversation, overlapping speech has a major
role. Based on the turn-taking model by Sacks et al. [3],
conversational partners aim to minimize overlaps and gaps in
their conversations. From to this model, overlaps occurs at
places of possible turn ends, either as “terminal overlaps” or
“simultaneous start”. Thus, overlapping speech is explained
as a result of turn-taking principles. This explanation is ex-
tended for different situational settings e.g. by [5], [6], where
short feedback signals confirming the statement of the current
speaker, are seen as “response token” overlaps. Furthermore,
several studies also analyses competitive overlaps, in which
the conversational partners compete for the turn [7], [8].
Many recent studies analyzed the phonetic structure of
overlapping speech and found that fundamental frequency,
intensity, speech rate and rhythm are important features charac-
terizing the overlaps as either being cooperative or competitive
[9], [8], [10]. Most of these studies concentrate on local
analyses investigating the acoustic characteristics next to or
directly at the overlap. Only a few studies incorporate for
example information on the duration of turns [11]. But the
relation of the length of utterances with the situational type of
overlap is not analyzed.
Former studies on overlapping speech concentrate to seek
an explanation of how overlapping speech works. They do
not analyze which consequences lead to an overlap or which
consequences the overlap has for the progress of the interac-
tion. The analyses especially disregard the length of utterances
where an overlap occurs (consequence lead to an overlap) and
which influence the affective state could have. Especially, in
[12] it is emphasized that affective states influence the turn-
taking behavior. Thus, problems in turn-taking can also be
traced back to changes in the affective state.
Furthermore, these studies are conducted only on human-
human interaction (HHI). Investigations on human-computer
interaction (HCI) do not consider overlapping speech as an
informative signal so far. But, to reach the target of a more
naturalistic interaction, future systems have to be adaptable to
the users’ individual skills, preferences, and current emotional
state [13], [14]. Lot of progress have been made in the area
of affect detection from speech, facial expression and gesture
[15]. For a fully naturalistic HCI, it is necessary to capture as
many human abilities as possible. Thus also linguistic features
gain considerable importance [16]. In an earlier study, we
could show that discourse particles, exchanged among the
interaction partners and used to signalize the progress of the
dialogue, are also used in naturalistic HCI, although the system
was not able to properly react to them [17]. The usage of these
cues is influenced by the user’s age and gender [18].
In this paper we will extend our analysis of linguistic
cues to overlapping speech and analyze the meaningfulness
of overlapping speech regarding the utterance length and the
user’s affective state change. We conducted a contrasting
study using human-human interaction (HHI) as well as HCI.
This will be the first step towards an automatic evaluation
of overlapping speech and could help future “Cognitive In-
focommunication” systems to understand the human better
[14]. Technical systems that use this extended recognition
of linguistic cues adapt to their users and thus become his
attendant and ultimately his companion [13], [19].
Based on these considerations, we investigate the following
three research questions in this paper.
Q1 Is overlapping speech occurring frequently enough in
our material to be analyzed in a dyadic conversation?
Q2 Is there any connection between overlapping speech
and the length of the previous utterance?
Q3 Is overlapping speech occurring at points where the
affective state is changing?
The remainder of the paper is structured as follows: In
Section II the utilized datasets are shortly described and
specific differences are emphasized. Afterwards, in Section III,
we describe the preparation of the date in terms of types of
overlap and affective annotation. In Section IV the results are
presented and discussed. Finally, in Section V, a conclusion of
our investigations and an outlook for further research is given.
II. UTILIZED DATASETS
A. Davero Corpus of Telephone-based Conversations
The dataset is described in detail in [20]. It is created
within a research project aiming to develop a technical system
that supports callcenter employees to respond appropriately to
the current affective state of the caller and was recorded in a
callcenter collecting real and authentic phone calls in German.
The calls embrace various topics, like information talks, data
change notifications, and complaints.
In order to allow a complete analysis of the conversation
both, agent and caller, were recorded acoustically. To gain real-
istic and high-quality recordings as well as to avoid disturbing
background noise, a separate recording place had been set up.
In total, 49 days ∗ 7 hours have been recorded. Since the
recorded phone conversations are real customer interactions
they had to be anonymized first, blanking out all personal
information. Furthermore, the start and end-times of each
dialog and overlapping speech segments were marked and each
utterance was assigned to its corresponding speaker (agent or
caller). To date, this dataset contains 1,600 dialogs with 27,000
individual utterances. The dialogs have an average length of
about 5 minutes with a standard deviation of ± 2 minutes.
B. SmartKom multi-modal Corpus
The SmartKom multi-modal corpus contains naturalistic af-
fects within a HCI [21]. The system responses were generated
by a Wizard-of-Oz (WOZ) setup. For our evaluations we use
German dialogs concerning a technical scenario, recorded in
a public environment. The database contains multiple audio
channels and two video channels (face and body in profile
posture). The primary aim of this corpus was the empirical
study of HCI in a number of different tasks. It is structured
into several sessions. Each session contains one conversation
and is approximately 4.5 minutes long.
This corpus has several annotation levels, of which for our
investigation the turn segmentation and an affective annotation
based on the acoustic channel is used [22]. The considered
set of the SmartKom corpus contains 438 emotionally labeled
dialogs with 12,076 utterances in total and 6,079 user utter-
ances. The utterances are labeled in seven broader affective
states: neutral, joy, anger, helplessness, pondering, surprise and
unidentifiable episodes. Unfortunately, the turn segmentation is
not time-aligned with the affective annotation.
III. PREPARATION OF DATASETS
A. Analysis of Overlapping Speech
We analyze overlapping speech as an additional pattern
of an interaction, as we assume that a valuable contribution
to the assessment of interactions is provided. Overlapping
speech refers to the case, when both speakers are talking
simultaneously.
1) Davero Corpus: By listening to examples of the Davero
corpus, four different situations (S) can be identified where
overlapping speech occurs:
S1 Short feedback, no interruption of the speaker
S2 Premature turn-taking at the end of the speaker’s turn
S3 Simultaneous starting after longer silence
S4 Barge-in, aiming to take the turn over
These situations are based on the descriptions of [11], distin-
guishing response tokens (S1), terminal overlaps (S2), simulta-
neous starts (S3) and competitive overlaps (S4). A prototypical
illustration is given in Figure 1.
In the first situation (S1), the listener just wants to give a
feedback. Lacking of other feedback methods (head nodding,
eye gaze), the listener has to give the feedback acoustically.
Thus no real turn-taking occurs. The second situation (S2) can
be seen as a functional turn-taking. The listener knows that
the speaker’s turn is due to end, but because of the missing
visual feedback the listener starts his turn a bit too early. In
this case just the alignment of the turn-taking is incomplete.
S3 is similar, both speakers start talking coincidentally after
a longer silence due to missing cues. S4 shows an disturbed
turn-taking. It describes the case where one speaker barges-in
while the other is still speaking to deliberately steal the turn
from that other speaker.
S1
S2
S3
Time
S4
Figure 1. Prototypes of the four different situations of two speakers (denoted
as – and –) for overlapping speech in HHI.
To evaluate the overlapping speech according to these
descriptions, we employed two labelers with psychological
background for the assessment. They could choose between
all four situations or describe a situation not covered by
the definitions. Of the currently available 27,000 utterances
in 1,600 dialogs 5,100 utterances (18.9%, 830 dialogs) are
marked to contain overlapping speech.
The final assessment is as follows: S1 has a share of
61.6%, S2 a share of 11.2%, S3 a share of 10.7%, and S4
a share of 16.6%. Furthermore, no additional situation was
selected by the annotators. As inter-rater reliability of the
crosstalk labelling we calculated a Krippendorff’s alpha of
0.63, a substantial reliability according to [23].
2) SmartKom Corpus: The SmartKom Corpus does not
have explicitly marked overlapping speech segments. By using
the segmentation annotation we could identify two types (T)
of overlapping speech (Figure 2):
T1 User interrupts the system.
T2 System interrupts the user.
T1
T2
Figure 2. Prototypes of the two different type of overlapping speech between
system (–) and user (–) in HCI.
In HCI the system is not seen as an equivalent dialog
partner [24], [25]. Therefore, the variety of types is not as big
as in HHI. From the 12,640 dialog acts within the SmartKom
corpus, we have 817 overlapping speech samples for T1 and
672 samples for T2.
B. Evaluation of the Affective States
We analyzed the affective states in both corpora based on
the Geneva Emotion Wheel by K. Scherer [26]. This is an
empirically tested instrument for the assessment of affective
states including 16 “emotional families”, which are arranged
on a circle along the axes dominance and valence.
1) Davero Corpus: To conduct the affective assessment,
we first employed a few annotators to manually segment the
recordings into single dialogs including the speaker turns. We
asked four annotators, all of them with psychological back-
ground, to assess the affective content of the single utterances.
We conducted several training rounds to make them familiar
with the used annotation scheme and the affective assessment
of acoustic data [27]. To support the annotation process, the
program ikannotate was used [28], [29]. This tool supports the
annotators by employing a three-step annotation process:
1. The annotator decides if the dominance is high or low.
2. The annotator decides for positive or negative valence.
3. The resulting quadrant of the wheel is displayed with
the containing emotion families. The annotator selects
one family among them to indicate the perceived
emotion.
For the present investigation, we only consider the labels from
step 1 and step 2, as we are only interested in a general
affective change. For the inter-rater reliability of the affective
annotation we calculated a Krippendorff’s alpha of 0.20 for
dominance and of 0.35 for valence. Although these numbers
seem to be quite low compared to other reliability values
known from content analysis, they are in line with results from
other research groups on affective analyses [27].Considering
the annotation results we observe a nearly balanced distribution
among the utterances. High dominance has a share of 59.0%
and low dominance of 41.0%, positive valence has a share of
53.5% and negative valence of 46.5%.
2) SmartKom Corpus: The SmartKom Corpus already has
an affective annotation [30]. Unfortunately, this annotation is
not on the same time-scale as the dialog act segments. Thus,
we have to perform an alignment of both annotation levels,
by using the individual timing information of both annotation
levels. Unfortunately, the corpus authors only measured the
annotation correctness by comparing the results of different
annotation rounds rather than calculating an inter-rater agree-
ment measure like Krippendorff’s alpha or Fleiss’ kappa. Their
calculated correctness is 45.52% [31]
Furthermore, in contrast to the Davero corpus, the affective
annotation in SmartKom is based on emotional categories.
Thus, we first have to deploy a mapping of the categories
used in SmartKom to our utilized dimensional categories of
dominance and valence. To conduct this mapping, we rely
on the Geneva Emotion Wheel [26], as it is also used for
the annotation of the Davero corpus. In analogy to similar
mappings [32], the assignment of the emotional categories to
the valence-dominance space is given in Table I. In contrast to
the Davero corpus, neutral is used as a category in SmartKom.
Table I. Mapping of SmartKom’s emotional categories to dominance and
valence.
category dominance valence
neutral 0 0
joy +1 +1
anger +1 -1
helplessness -1 -1
pondering -1 +1
surprise -1 +1
unidentifiable 0 0
In total we have 14,298 affective segments. Most of these
segments (59.7%) are neutral. The distribution on the dom-
inance dimension is 30.7% low and 69.3% high dominance.
Positive valence has a share of 39.0% positive and negative
valence a share of 61%. Thus, the emotional content within this
corpus is shifted towards negative valence and high dominance.
IV. RESULTS
A. Q1: Occurrence of Overlapping Speech
To answer the first question, we calculated the ratio of
overlapping speech segments and number of utterances. For the
Davero corpus we have 27,000 utterances and 5,100 of them
contain overlapping speech. Thus, we have a share of 18.9%
for overlapping speech segments. If we consider the dialog
level, we have 1,600 dialogs in total of which 830 dialogs
contain overlapping speech segments. This results in a share
of 51.9%.
The German part of the SmartKom Corpus has a total num-
ber of 12,076 utterances with 1,489 occurrences of overlapping
speech. This results in a share of 12.3% overlapping speech
utterances for this HCI. As we only take into account the
overlapping speech, we have 6,347 user utterances and 817
utterances contain overlapping speech.
Thus, we can conclude that overlapping speech is occur-
ring frequently and the first question: “Is overlapping speech
occurring frequently enough to be analyzed in a dyadic con-
versation?” is approved.
B. Q2: Overlapping Speech and Utterance Lengths
This investigation is triggered by the assumption that
overlapping speech is occurring because the actual speaker is
talking too long and the listener wants to get the turn. To
investigate this assumption, we calculated the mean length of
the utterance where the overlapping speech occurs (utt
ov erlap
)
in relation to all other utterances (utt
remain
) of this speaker
within a dialog. Afterwards, we averaged over all dialogs and
calculated the difference between both averaged mean lengths:
∆len = len
utt
overlap
− len
utt
remain
(1)
This calculation is performed for each of the previous iden-
tified different situations separately and averaged afterwards
(∆len). Additionally, we used the non-parametric Mann-
Whitney-U-Test, to test the significance of the difference
within the utterance lengths. The star denotes the significance
level: ** p < 0.001.
1) Davero Corpus: From Figure 3 it can be seen, that in
two situations, the length of the utterance with overlapping
speech is different from other utterances of the same speaker.
For S1, the len
utt
overlap
is significantly longer than for other
utterances. In this situation one speaker gives statements that
are just confirmed by the listener without interrupting the
speaker. Thus, the speaker can continue his turn. The presence
of this type of overlapping speech does not indicate a change
in the progress of the dialog. The same statement can be made
for S2, where the len
utt
overlap
is significantly shorter than for
other utterances. The overlapping speech in both situations is
just occurring because only the acoustic channel can be used
to negotiate the turn-taking. Thus, the length of an utterance
together with the information of an occurring speech overlap
cannot be used as an indicator for dysfunctional conversation.
S1 S2 S3 S4
−2
0
2
4
** **
Overlapping Speech Situation
∆len [s]
Figure 3. Difference of the utterance length for the four defined overlapping
speech situations and the average utterance length in the Davero corpus, stars
indicate a significant difference.
2) SmartKom Corpus: From Figure 4 it can be seen that
for type T1 the system utterance with the overlapping speech
segment (len
utt
overlap
) is significantly longer than the other
system utterances. Thus, it can be assumed that for a pos-
itive interaction outcome and fluent conversation the system
prompts shouldn’t be too long.
For the second type, where the system interrupts the users,
the users’ utterance length containing overlapping speech is not
significantly different from other user’s utterances. Therefore,
we assume that these interruptions of the system are caused
by operator errors of the WOZ-system.
Regarding our second research question, we can state that
there is a significant correlation between overlapping speech
and the length of the previous utterance in both HHI and HCI.
C. Q3: Overlapping Speech and Affective Changes
To investigate the affective change at the point where
overlapping speech occurs, we take into account the observed
affective states in two preceding utterances and compare it to
T1 T2
0
1
2
3
**
Type of Overlapping Speech
∆len [s]
Figure 4. Difference of the utterance length for the two types of overlapping
and the average utterance length in SmartKom. The stars indicate a significant
difference.
the observed affective states in the two succeeding utterances.
We distinguish between high (+1) and low (-1) dominance and
positive (+1) and negative (-1) valence. Utterances that do not
have an affective label or are labeled as neutral are assigned a
0. Thus, we can calculate the difference between the affective
states of the preceding utterances and the succeeding utterances
for an overlapping speech segment:
∆Affect = Affect
before overlap
− Affect
after overlap
(2)
Afterwards, we average over all segments (∆Affect). The sig-
nificance of the affective change is tested by using the Mann-
Whitney-U-Test. The stars denotes the significance level: *
p < 0.01 and ** p < 0.001.
S1 S2 S3 S4
0
0.5
1
**
Overlapping Speech Situation
∆Dom
Figure 5. Dominance change at the point where overlapping speech occurs,
stars indicate a significant affective state change
1) Davero Corpus: Analyzing the change of affective states
in connection with overlapping speech only in S3 (simulta-
neous starting after longer silence) a significant change in
the affective state can be observed, see Figure 5. A possible
interpretation for this observation is that the dominance level
is dropping. Having a deeper analysis of the data, we can state
that the dominance level of the interrupter is raising, while the
dominance of the speaker whose turn is interrupted is slightly
decreasing. In this case, the overlapping speech event could be
a good marker for identifying changes in dominance. For all
other situations of overlapping speech, the dominance of the
two speakers is not influenced by overlapping speech.
S1 S2 S3 S4
−0.2
0
0.2
Overlapping Speech Situation
∆Val
Figure 6. Valence change at the point where overlapping speech occurs in
the Davero corpus.
For the change of the speaker’s valence, we can state
that there is no significant connection with the occurrence of
overlapping speech, cf. Figure 6. This could be expected as
overlapping speech is related to the turn-taking behavior of
the speakers and the dominance of a speaker is seen as the
underlying mechanism to regulate the turn-taking [12].
T1 T2
−1
−0.5
0
** **
Type of Overlapping Speech
∆Dom
Figure 7. Dominance change at the point where overlapping speech occurs in
the SmartKom Corpus. The stars indicate a significant affective state change.
2) SmartKom Corpus: Regarding Figure 7, it can be seen
that the dominance for both types is significantly higher after
the overlapping speech segment than before. This it quite
obvious for the case where the user actively interrupts the
system, but when the system interrupts the user this seems
quite unintuitive and can only be explained in connection
with the valence change. Regarding the valence change (cf.
Figure 8), we can state that after the overlapping speech
the user is significantly more moved to negative values. This
finding in connection with a higher dominance shows that it
can be assumed that the user is more angry after overlapping
speech, either because he wants to speak and interrupts the
system, or he is annoyed because the system interrupts him.
T1 T2
0
0.5
1
** *
Type of Overlapping Speech
∆Val
Figure 8. Valence change at the point where overlapping speech occurs in
the SmartKom Corpus. The stars indicate a significant affective state change.
Regarding our third research question: “Is overlapping
speech occurring at points where the affective state is chang-
ing?”, we can conclude that in HHI only changes in the
dominance are related to overlapping speech, whereas in HCI
significant changes in both affective dimensions, dominance
and valence, can be observed.
V. CONCLUSION
In this paper, we present a first study investigating over-
lapping speech effects in both HHI and HCI. The analyses are
conducted on a dataset of realistic HHI containing telephone
based conversations and the well-known SmartKom Corpus
of naturalistic HCI. We could show that in both datasets
overlapping speech occurs frequently enough to be analyzed
with a share of 18.9% for HHI and 12.3% for HCI. For the
investigated HHI, this share is in-line with the results of other
research groups [11], [33]. The amount of overlap in HCI is
a bit lower but still sufficient. For this no numbers of other
researchers are to our best knowledge reported in the literature.
Based on the description of situational settings, we first an-
alyzed the correlation between the length of overlap-preceding
utterances and the occurrence of overlap. As a result of our
first analysis, we could expose significant relations to the
length of the spoken utterances and changes in the affective
state of the conversational partners. In HHI we could find a
significant correlation between overlapping speech as feedback
and premature turn-taking. Also in HCI a significant corre-
lation is found between overlapping speech and the length
of system utterances. The user’s utterance-lengths did not
show significant correlations for the occurrence of overlaps,
we assume that these overlaps are just caused by operator
malfuntions, as the SmartKom data are recorded in a WOZ-
scenario. And now pre-defined design rules are given for the
wizards how to use overlap [21].
Secondly, we analyzed the correlation of affective changes
at in the surrounding of the overlap in both types of inter-
actions. For this investigation, we showed that overlapping
speech goes along with changes in the affective states of
dominance and valence in certain situations. In HHI only
the situation where both speakers start simultaneously after a
longer pause effects a significant change of dominance. For the
valence dimension no significant correlation could be found. In
the investigated HCI both affective dimensions, dominance and
valence, show a significant correlation to overlapping speech
in both situation types.
From these results, we are able to derive some rules for
the organization of interactions: In telephone based HHI the
utterances should not be too long and the listener should be
encouraged to give feedback. This avoids competitive barge-
in overlaps. For HCI, the system should not talk to long as
for all overlapping speech segments, an affective change to
higher dominance and negative valence of the speaker can be
observed. But this kind of affective change should be avoided.
To evaluate these statements for their generality, a broader
investigation including additional corpora has to be conducted.
A possible application of our investigations in HHI and
HCI is the identification of parts where the affective state
changes based on the knowledge of overlapping speech and the
dialog course: As e.g. situation S3, where both speakers start
simultaneously, can be easily identified by duration analysis,
this knowledge can be used to find affective material for further
emotional analyses.
In our further research activities, we will develop a robust
automatic identification of the different types of overlap.
Together with the recognition of the user’s affective state,
we are a step further to future Cognitive Infocommunication
systems acting as a companion towards human users [13], [14].
VI. ACKNOWLEDGEMENTS
The work presented in this paper was done within the
Transregional Collaborative Research Centre SFB/TRR 62
‘Companion-Technology for Cognitive Technical Systems’
funded by the German Research Foundation (DFG).
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