PONE-D-22-20948Impact of chatbot facial emotions changes on user attention and reaction timePLOS ONE

Dear Dr. Bortko,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

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PLOS ONE

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This work was supported by the National Science Centre of Poland, Decision No.

2017/27/B/HS4/01216 ( J.J., K.B.) and this research was supported by ZUT Highfliers

School /Szko la Or l´ow ZUT/ project co-ordinated by Dr. Piotr Sulikowski, within the

framework of the program of the Minister of Education and Science /Grant No.

MNiSW/2019/391/DIR/KH, POWR.03.01.00-00-P015/18/, co-financed by the

European Social Fund, the amount of financing PLN 1,704,201,66 (K.F.).

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This work was supported by the National Science Centre of Poland, Decision No. 2017/27/B/HS4/01216 ( J.J., K.B.) and this research was supported by ZUT Highfliers School /Szkoła Orłów ZUT/ project co-ordinated by Dr. Piotr Sulikowski, within the framework of the program of the Minister of Education and Science /Grant No. MNiSW/2019/391/DIR/KH, POWR.03.01.00-00-P015/18/, co-financed by the European Social Fund, the amount of financing PLN 1,704,201,66 (K.F.).

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Partly

Reviewer #2: Yes

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2. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: N/A

Reviewer #2: Yes

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3. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: No

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4. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: No

Reviewer #2: Yes

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5. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: This paper analyses the impact of emotional changes in a chatbot representation on users’ attention and reaction times. The study deals with a very interesting and timely topic. The literature on the impact of conversational agents is rapidly expanding in different areas, and the question of how their visual appearance affects user experience is crucial. However, I have some concerns about the research execution, the paper’s structure, and the interpretation of the findings.

1. In the abstract and the introduction sections, the paper appears to focus on how specific visual characteristics (in this case, changes in emotional expressions) of a chatbot attract users’ attention and make the chatbot get noticed among many other possible competing visual information displayed on a website or an online platform. The authors indeed state: “While chatbots compete with other graphic elements within websites or applications, attracting user attention is a challenge […]. Drawing attention to a chatbot area localised within the periphery area can be based on the usage of different visual characteristics […] Expressed emotions can be another technique to attract user attention […]”. However, results are mainly discussed in terms of perceptual processes, such as emotion detection and recognition in the periphery of the visual system. Both in the introduction and discussion sections, the authors should better clarify the link between emotional change detection and users’ attention. If the main goal was to understand which visual characteristics of a chatbot make it more noticeable and direct users’ attention towards it, how should reactions times to changes in the chatbot’s emotional expressions measure this? It is likely that participants are aware of the presence of the chatbot regardless of the emotion displayed but that they are only detecting a change to positive emotion faster than negative emotions.

2. It is also unclear whether the authors refer to visual characteristics in terms of “emotional change” or “expressed emotional states”. As mentioned in the text, the goal of the study was to verify “the impact of emotional changes within a chatbot’s face on user attention and reaction time”. The experiment setup seems to be heading in this direction. Participants were indeed instructed to click the mouse when they perceived a “change” in the chatbot’s emotional expression. Results are also partially discussed in terms of how fast participants were in detecting this change (e.g., “As the emotion changes were displayed to users in sequences, the study revealed that the emotions of happiness, surprise and fear with each successive change led to a decrease in the average response time of users”). On the other hand, though, the authors discuss their results in terms of expressed emotional state (e.g., “When developing a humanoid chatbot model that can express certain emotions, it is worth considering which emotions should be selected for specific messages if a specific reaction in the user is the desired”). In this case, the authors discuss the results in terms of which type of emotional state displayed by a chatbot is more effective in eliciting a specific reaction (authors should also clarify to the reader what they mean by “specific reaction”: reaction times? Emotional and/or social response?). Therefore, it is unclear whether the focus is on the effect of users’ detection of changes in emotions or on the impact of the emotional state displayed by the chatbot. The authors should clarify this point.

3. I find it challenging to understand the transition from talking about chatbots used in online platforms and websites for communication purposes to the guidelines for game designers outlined in the conclusion section. First, if the authors intend to generalise their results to the context of video games, they should explain the role of avatars displayed in the periphery. Second, they state: “In the excitement of gameplay in MMO games or even simulators, e.g., piloting a plane or driving a vehicle, every fraction of second counts. By introducing appropriate content expressing individual emotions, we can extend the reaction or effectively shorten it”. This conclusion was quite confusing to me. Specifically, it is unclear whether the outcome variables (user attention and reaction times) are investigated in relation to the central task or the chatbot (drawing the user’s attention towards it). Why should a peripheral avatar displaying certain emotions (or emotional changes) affect the performance on the simulation task (e.g., driving or piloting) in this case?

4. The authors leave out important information regarding the chatbot’s design. There needs to be much more discussion on the chatbot’s appearance. In Figure 1, the chatbot appears as a gender-neutral emoticon, though in the text, it is specified that they used male and female faces (Male 1, Male 2, Female 1, Female 2). In the introduction, the authors refer to anthropomorphism and the uncanny valley theory, and further refer to the chatbot visualisation in terms of “graphic avatar” and “humanoid chatbot”, which makes me assume that they used computer-generated human-like faces. Details on the chatbots’ appearance should include the software and technique used and information on realism (e.g., in terms of texture) with which they were created. The degree of realism of a human-like digital entity generates very different reactions in the observers and it has different implications in terms of the uncanny valley effect. The authors should clarify this section to avoid confusion.

5. In the introduction section, the authors refer the potential of chatbots’ human-like features to help create a more authentic and natural interaction and communication. The authors may consider the “computers as social actors” and “social presence” theory as possible theoretical framework to explain why embedding social cues (e.g., human-like avatar showing emotional expressions) in chatbots’ design enhances users’ engagement and promotes a more natural interaction.

6. I found the manuscript poorly organised. Many sentences disrupt the flow of the text and raise several questions. A couple of examples:

- “The visualisation of chatbots and their social features, should target users’ expectations, ultimately avoiding frustration and dissatisfaction”. Expectation to what? Also, why are the authors here referring to frustration and dissatisfaction? I would expect a link between the focus of the study (users’ attention) and these outcomes.

- “Additionally, there is positive relationship between human likeness and knowledge”. What does this mean and how is it related to what the authors are saying?

7. The language is unclear, with many imprecisions and hard-to-read or incomplete sentences, making it difficult to follow. I would recommend language editing.

8. Overall, I think the authors are addressing a very interesting topic, but need to restructure the introduction and discussion and clarify some main points before drawing any conclusion. The theories and related findings are indeed sparse and therefore do not support the research framework of this study. Hypotheses development is also not substantiated. Due to these critical issues, the discussion fails to show relevance to the literature as the links between predictions and findings with related theories and findings from similar works are missing.

Reviewer #2: This article presents a study that evaluates the differences in time reaction in the detection of a chatbot (presented in a periphery area of the screen) if it shows different emotions.

The authors provide detailed motivations and references, which led to the experiment's construction, in a precise and logical way. The methodology and results appear sound.

However, as per “e PLOS Data policy” “all data underlying the findings described in the manuscript need to be fully available”, but I was not able to find them, either reported in the article or through an indication of where they could be found (e.g. public repository); also the Data Availability Statement does not describe where the data can be found. If specific reasons make the data not disclosable, they should be described accurately. If not, data or an indication of where they can be consulted should be included.

Furthermore, there are some minor issues I think need to be addressed before publication:

1) the sample should be described with more details (es. gender, inclusion and exclusion criteria)

2) some captions and figures are unclear and are missing measurement units (e.g. ms):

2a) fig 2 B the color code of the chart and the legend of the two histograms on top and on the right should be included

2b) fig 2 C does not look like a “scatterplot”, I suggest an alternative definition. Furthermore, a better definition of “reaction” is needed and the caption is unclear

2c) fig 3 A in the caption “shows two groups of emotions (positive and negative) along with the coverage of individual groups of emotions” should be more explicit; a description of the light green and light red should be provided also in a legend

2d) fig 3 B the color code of the chart and the legend of the two histograms on top and on the right should be included

3) In the following phrases

3a) “In fact, Mori observed an increased sensitivity to defects in a human-like form”: which type of defects are they referring to?

3b) “Additionally, there is a positive relationship between human likeness and knowledge”: the meaning is obscure

3c) “In detection, however, while happiness and surprise are still well detected, fear is also a well detected expression”: there seems to be an error here

3d) “Both of these emotions can be classified as positive, while the others, which were also present in the study, i.e., anger, disgust, sadness, and fear, are negative or pejorative”: the phrase does not link with the one before

3e) An important aspect is to increase the naturalness of the chatbot’s communication with the user: the phrase does not link with the one before

3f) “McCrickard et al. discussed utility as a value provided by the peripheral system as a whole and did not directly manipulate utility as part of their experiment, whereas we consider utility as the meaning of the content of the individual gaps”: the concept of utility should be better defined

4) Proofreading is suggested. For example, the form of the following phrases should be reviewed:

4a) “The graphic avatar in the chatbot field will have a different impact on a conversation than a conversation with a human and increases the fluency of conversation”

4b) “This secondary task is usually a given, with the task supported by the peripheral system being evaluated”

4c) “In real systems, the chatbot, as well as system messages or in-video-game messages, aimed at helping users or players, is targeted at a more accurate peripheral search and identification tasks while performing a central search”

4d) “Starting the analysis at the base, we can conclude in Figure 2 (A)“

4e) ”It can be seen here that the vast majority of reaction times ranged from 0.36 to 0.52 s. In this interval, most reactions were to the emotion of surprise”

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Reviewer #1: No

Reviewer #2: No

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PONE-D-22-20948R1Impact of changes in chatbot's facial expressions on user attention and reaction timePLOS ONE

Dear Dr. Bortko,

Thank you for submitting your manuscript to PLOS ONE. After careful consideration, we feel that it has merit but does not fully meet PLOS ONE’s publication criteria as it currently stands. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process.

==============================

One Reviewer has suggested minor revision to the manuscript. I invite Authors to provide modifications in order to proceed. 

==============================

Please submit your revised manuscript by Jun 12 2023 11:59PM. If you will need more time than this to complete your revisions, please reply to this message or contact the journal office at plosone@plos.org. When you're ready to submit your revision, log on to https://www.editorialmanager.com/pone/ and select the 'Submissions Needing Revision' folder to locate your manuscript file.

Please include the following items when submitting your revised manuscript:

• A rebuttal letter that responds to each point raised by the academic editor and reviewer(s). You should upload this letter as a separate file labeled 'Response to Reviewers'.
• A marked-up copy of your manuscript that highlights changes made to the original version. You should upload this as a separate file labeled 'Revised Manuscript with Track Changes'.
• An unmarked version of your revised paper without tracked changes. You should upload this as a separate file labeled 'Manuscript'.

If applicable, we recommend that you deposit your laboratory protocols in protocols.io to enhance the reproducibility of your results. Protocols.io assigns your protocol its own identifier (DOI) so that it can be cited independently in the future. For instructions see: https://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols. Additionally, PLOS ONE offers an option for publishing peer-reviewed Lab Protocol articles, which describe protocols hosted on protocols.io. Read more information on sharing protocols at https://plos.org/protocols?utm_medium=editorial-email&utm_source=authorletters&utm_campaign=protocols.

We look forward to receiving your revised manuscript.

Kind regards,

Stefano Triberti, Ph.D.

Academic Editor

PLOS ONE

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Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

1. If the authors have adequately addressed your comments raised in a previous round of review and you feel that this manuscript is now acceptable for publication, you may indicate that here to bypass the “Comments to the Author” section, enter your conflict of interest statement in the “Confidential to Editor” section, and submit your "Accept" recommendation.

Reviewer #1: (No Response)

Reviewer #2: All comments have been addressed

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2. Is the manuscript technically sound, and do the data support the conclusions?

The manuscript must describe a technically sound piece of scientific research with data that supports the conclusions. Experiments must have been conducted rigorously, with appropriate controls, replication, and sample sizes. The conclusions must be drawn appropriately based on the data presented.

Reviewer #1: Yes

Reviewer #2: Yes

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3. Has the statistical analysis been performed appropriately and rigorously?

Reviewer #1: N/A

Reviewer #2: Yes

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4. Have the authors made all data underlying the findings in their manuscript fully available?

The PLOS Data policy requires authors to make all data underlying the findings described in their manuscript fully available without restriction, with rare exception (please refer to the Data Availability Statement in the manuscript PDF file). The data should be provided as part of the manuscript or its supporting information, or deposited to a public repository. For example, in addition to summary statistics, the data points behind means, medians and variance measures should be available. If there are restrictions on publicly sharing data—e.g. participant privacy or use of data from a third party—those must be specified.

Reviewer #1: Yes

Reviewer #2: Yes

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5. Is the manuscript presented in an intelligible fashion and written in standard English?

PLOS ONE does not copyedit accepted manuscripts, so the language in submitted articles must be clear, correct, and unambiguous. Any typographical or grammatical errors should be corrected at revision, so please note any specific errors here.

Reviewer #1: Yes

Reviewer #2: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: I would like to thank the authors for their effort in improving the manuscript and for clarifying some main points. However, there are still some issues that the authors should address:

� At p. 2/13 “The ’social presence’ theory [11] suggests that the degree of social presence in a communication medium can affect the perceived level of social presence in the interaction”. This sentence is unclear as the authors are saying that “the degree of social presence […] can affect the level of social presence”, which is a tautology. The social presence theory suggests that the degree to which a medium (such as a chatbot) is designed to look and act more like a human, with features such as a human-like appearance, facial expressions, and gestures, positively impact the level of social presence perceived in the interaction. As a result, users may feel like they are engaging in a more natural and authentic conversation, as if they were talking to a real human instead of a machine.

� At p. 2/13 “In fact, Mori [12] observed a degree of defect proneness in near-human forms an ”uncanny valley” in what otherwise follows from the relationship between anticipation and familiarity”. That is not entirely precise. The Uncanny Valley (UV) hypothesis refers to the relationship between an entity’s human-likeness and familiarity (not between anticipation and familiarity). The human-likeness/familiarity relationship is correctly discussed by the authors in the following sentence “Mori observed that the more human-like a technological object such as a robot is, the more familiar it seems; however, this is true only up to a certain point, at which even subtle deviations from human norms can make the object look disturbing”.

“Anticipation”, “perceptual difficulty”, as well as “increased sensitivity to defects in a human-like form”, mentioned in this paragraph, actually refer to different proposed explanations of the UV effect. First, “anticipation” plays a key role in the expectation violation explanation of the uncanny valley. The expectation violation explanation suggests that the negative response to an entity in the UV occurs when it violates the expectations that humans have for how a human-like entity should behave and interact based on their past experiences and knowledge of human behaviour. Second, the sentence “Perceptual difficulty in distinguishing between a human-like object and its human counterpart would produce negative affect” refers to the “categorization ambiguity” explanations of the UV. When an entity is difficult to categorize as either animate or inanimate because it possesses some but not all of the features of a living entity, this creates a sense of ambiguity, which can lead to discomfort and unease. Third, “Mori observed an increased sensitivity to defects in a human-like form”. The higher sensitivity to deviations from typical human norms for more human-like characters is part of the perceptual mismatch explanations, according to which the UV effect is caused by any perceptual mismatch in the digital entity’s appearance. In this case, as humans interact with entities that resemble humans to a greater degree, they become more attuned to the nuances of human behaviour and appearance. This heightened sensitivity can increase awareness of deviations (mismatches) from typical human norms. [If you wish to know more, please see Katsyri et al. (2015) “A review of empirical evidence on different uncanny valley hypotheses: support for perceptual mismatch as one road to the valley of eeriness”.]

Here I would suggest the authors keep it simple by just referring to the relationship between human-likeness and familiarity, without digging into the different explanations.

Furthermore, I would change the sentence “The hypothesis suggests that humanoid objects, including chatbots, which appear almost, but not exactly, like real human beings, may evoke strange or strangely familiar negative as well as positive feelings in observers” removing the reference to positive feeling, which creates confusion while talking about the UV effect.

Finally, as observed by the other reviewer in the first step of revisions, the meaning of “Additionally, there is a positive relationship between human likeness and knowledge”: is unclear. I would suggest the author to remove it.

� At p. 3/13 the concept of utility is still unclear. First: “In real systems, chatbots […] are able to perform more accurate peripheral search and identification tasks while performing a central search”. I think there is a mistake here as it seems that are chatbots perfoming peripheral search and identification tasks. I guess the authors wanted to say that in real systems, given that chatbots are usually located peripherally, they require the users to perform a peripheral search while performing a central task (which is in line with the attention-utility issue discussed by McCrickard and colleagues).

The following phrase “Mimicked expressions of emotions are signals of high biological value” does not link with the one before and the one after and drift attention from the definition of the utility concept. I would suggest removing it.

The authors then discuss utility, but its definition is still hard to catch. Utility refers to a system's usefulness to its users or customers. What McCrickard and colleagues discuss in the context of peripheral system design, is that utility refers to the ways in which peripheral cues or messages help users accomplish their goals without requiring their full attention. Therefore, the sentence “Utility, like usability, can be evaluated as an aspect of human-computer interaction for the purpose of identifying aspects of this interaction that can be improved with the help of evaluation methods” still doesn’t capture the definition of utility.

Also, the difference in the conceptualization of utility between McCrickard and colleagues, and the one provided by the authors is unclear. What are the authors referring to when they talk about “individual gaps”? Once addressed this issue, I would place this section after the definition of utility for better clarity.

� At p. 3/13 there is a “s” after the [25].

� At p. 9/13 there is a missing in-text reference number (McCrickard et al.).

Reviewer #2: (No Response)

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7. PLOS authors have the option to publish the peer review history of their article (what does this mean?). If published, this will include your full peer review and any attached files.

If you choose “no”, your identity will remain anonymous but your review may still be made public.

Do you want your identity to be public for this peer review? For information about this choice, including consent withdrawal, please see our Privacy Policy.

Reviewer #1: No

Reviewer #2: No

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Impact of changes in chatbot's facial expressions on user attention and reaction time

PONE-D-22-20948R2

Dear Dr. Bortko,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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Stefano Triberti, Ph.D.

Academic Editor

PLOS ONE

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