Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study

Lukas D. Lopez; Eric A. Walle; Gina M. Pretzer; Anne S. Warlaumont

doi:10.1371/journal.pone.0242232

Peer Review History

Original SubmissionJune 26, 2020
24 Aug 2020 Decision Letter - Iris Nomikou, Editor PONE-D-20-19792 Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study PLOS ONE Dear Dr. Lopez, Thank you for submitting your manuscript to PLOS ONE. I have now received two reviews and although both reviewers agree that the manuscript has merit they have raised a few issues that I feel should be addressed. I have decided for major revision since one of the reviewers has proposed additional analysis. Therefore, we invite you to submit a revised version of the manuscript that addresses the points raised during the review process, which can be summarised as follows: 1) Consider a stronger motivation of the study highlighting the importance of ecologically valid observations and the overlooked role of context in language learning. 2) Reviewer 2 raises a methodological question about the use of sequential analysis. Please either consider further analysis or reply justifying your decision. Reviewer 2 also points to a couple of data that would interesting to report such as the number of vocalisations occurring which were not responded to by the mother. 3) Both reviewers suggest some additions to the discussion, such as linking to existing literature considering the role of activity context and also considering potential applications of your research. Please go over the reviews and reply to all of the comments and questions raised, either in the manuscript or in your rebuttal letter. Please submit your revised manuscript by Oct 08 2020 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 you would like to make changes to your financial disclosure, please include your updated statement in your cover letter. Guidelines for resubmitting your figure files are available below the reviewer comments at the end of this letter. 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: http://journals.plos.org/plosone/s/submission-guidelines#loc-laboratory-protocols We look forward to receiving your revised manuscript. Kind regards, Iris Nomikou, Ph.D. Academic Editor PLOS ONE Journal Requirements: When submitting your revision, we need you to address these additional requirements. 1. Please ensure that your manuscript meets PLOS ONE's style requirements, including those for file naming. The PLOS ONE style templates can be found at https://journals.plos.org/plosone/s/file?id=wjVg/PLOSOne_formatting_sample_main_body.pdf and https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf 2. Please provide additional details regarding participant consent. In the ethics statement in the Methods and online submission information, please ensure that you have specified whether consent was informed. 3. Please include captions for your Supporting Information files at the end of your manuscript, and update any in-text citations to match accordingly. Please see our Supporting Information guidelines for more information: http://journals.plos.org/plosone/s/supporting-information [Note: HTML markup is below. Please do not edit.] 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: Yes Reviewer #2: Yes ******** 2. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes Reviewer #2: Yes ****** 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: Yes ****** 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: Yes Reviewer #2: Yes ****** 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: Thank you for the opportunity to review the manuscript titled “Adult response to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study” The study focused on relations between adult responses to infant vocalizations in the context of a naturalistic home environment using LENA. I think the study is very valuable and adds to prior literature on parent-infant interactions using ecologically valid methods. A few questions and suggestions came up for me while reading the manuscript that I think, if addressed, could strengthen the paper. First, I think the framing and motivation of the paper isn’t strong enough and could use more nuance. The study is motivated by the naturalistic method, suggestions that such method is more ecologically valid than the structured lab environment. I wholeheartedly agree. There aren’t enough studies focused on what parents actually do in the confines of their homes and how that shifts across the day. However, it isn’t that lab studies don’t generalize at all or capture something completely artificial and different from naturalistic environments. Lab studies, rather, capture a specific aspect of interactions that is found in the home environment. Tamis-LeMonda and colleagues’ paper (citation 16 in the manuscript) on methods shows that structured observations (which were done in the parents home, but are similar to structured observations in lab environments) capture the highest consecutive five minutes of interaction in the home. They capture the chattiest moments, that is. It is no surprise that then years of studies on language input during structured observations predict child language development. it isn’t the the lab methods are invalid, they do capture something meaningful. They just don’t capture ecology, fluctuation of talk across the day, the setting and activity within which interactions take place and learning occurs, the most interesting and embodied aspects of learning. The aspects of children’s context that are largely ignored by developmental psychologists who focus on language but are constantly articulated by cultural psychologists and linguistic anthropologists are necessary. This point I think is important to address in the introduction, and necessitates a stronger motivation for the study to be articulated by the authors. Second, information presented about contingent responsiveness is incomplete. It seems that the authors captured base rates of responses, that is, frequencies of how many times parents responded to the different types of vocalizations. In work on contingent responsiveness, typically researchers would go a step further and conduct sequential analyses to gather probabilities of mother responding to infant vocalizations. Such probabilities account for base rates of behaviors, and can be used in analyses predicting language outcomes. These probabilities matter because they differentiate mothers who respond to an infant twice (but infants’ total vocalizations are 10) from a mother who responds to an infant twice (but infants’ total vocalizations are 3). The second mother is more responsive than the first. On line 305 the authors state that they are not seeking to detect causal effects of infants’ vocalizations, which is a slight mischaracterization of the baseman’s GSEQ method. They are probabilities, and they take into account all of the mother and infant talk. On page 29, the authors use the language “elicit” which appears causal anyhow. So my questions are: if authors are trying to extend prior literature into the home and see if patterns found in structured observations in lab (or home!) mirror, why not use established methods for contingent responsiveness? Regardless, the authors should then also report how many infant vocalizations occurred in each segment that the mothers did not respond to to give readers a sense of the overall interaction. In the context of the home, unlike the structured context, mothers may attend to other tasks, and interactions may be fluid, comprised of smaller bouts perhaps. I would presume that mothers would have lower rates of responding to total number of infant vocalizations in the home than in the lab, where they have little else to do but interact, and my hypothesis would also be that bouts of very contingent interactions would focus on specific activities, like book sharing or play. Finally, I appreciate that the authors noted the types of activities that occurred in the segments chosen, and I think that those should be highlighted. The study focuses on language interactions in the context of everyday life, and so interpretation of input in the context of play specifically (which comprised most segments it appears) is meaningful and necessary. It should also then be linked to prior work on language input by activity context, perhaps in the discussion. Reviewer #2: This is a well written manuscript that details the findings for in home parent-infant vocal interactions and their relation to language outcomes. This is an area of research that is underrepresented in the literature, as the majority of studies have been conducted in the lab. The meticulous coding captures specific responses (recasts, expansions) to more advanced infant vocalizations (canonical vocalizations) that support language development. The findings reveal important moment to moment vocal exchanges that can support positive outcomes. I appreciate the limitations discussed by the authors, but I would also suggest that there are potential applications of their research that they could elude to in the discussion. I agree that these are just short snippets of exchanges, but the importance of uncovering which specific vocalizations and feedback (loops) is significant for understanding how parents support language in day to day interactions. ****** 6. 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: Yes:** Yana Kuchirko Reviewer #2: No [NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.] While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step. https://doi.org/10.1371/journal.pone.0242232.r001
Revision 1
16 Sep 2020 Author Response 9/15/2020 Dear Editor Nomikou, We submit for your consideration a revision of our manuscript, titled “Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study,” submitted as a Research Article to PLOS ONE. In what follows, our responses to each point are detailed in italics, with the reviewers’ comments given in quotes. Thank you once again for your thoughtful consideration of our work, and for the opportunity to improve it. We feel that the paper has been improved with the benefit of the feedback that we have received and look forward to your assessment. Sincerely, Lukas Lopez (on behalf of all co-authors) Department of Psychological Sciences University of California, Merced Merced, CA 95343, USA Email: llopez65@ucmerced.edu Replies to Reviewer: Reviewer #1: “First, I think the framing and motivation of the paper isn’t strong enough and could use more nuance. The study is motivated by the naturalistic method, suggestions that such method is more ecologically valid than the structured lab environment. I wholeheartedly agree. There aren’t enough studies focused on what parents actually do in the confines of their homes and how that shifts across the day. However, it isn’t that lab studies don’t generalize at all or capture something completely artificial and different from naturalistic environments. Lab studies, rather, capture a specific aspect of interactions that is found in the home environment. Tamis-LeMonda and colleagues’ paper (citation 16 in the manuscript) on methods shows that structured observations (which were done in the parents home, but are similar to structured observations in lab environments) capture the highest consecutive five minutes of interaction in the home. They capture the chattiest moments, that is. It is no surprise that then years of studies on language input during structured observations predict child language development. it isn’t the the lab methods are invalid, they do capture something meaningful. They just don’t capture ecology, fluctuation of talk across the day, the setting and activity within which interactions take place and learning occurs, the most interesting and embodied aspects of learning. The aspects of children’s context that are largely ignored by developmental psychologists who focus on language but are constantly articulated by cultural psychologists and linguistic anthropologists are necessary. This point I think is important to address in the introduction, and necessitates a stronger motivation for the study to be articulated by the authors.” We thank the reviewer for the positive assessment of the methodologies used in the present paper and the excellent suggestion to further highlight the behavioral ecology of the observed behaviors. We agree that while in-lab observations capture meaningful caregiver behaviors, studies in the naturalistic home environment capture the ecology in which these behaviors normally transpire, including a much greater range of settings and activities such as cultural contexts and caregiving practices. We now reference work from cultural psychology and anthropology that highlight these points and have emphasized the utility of naturalistic recordings for capturing a variety of learning ecologies in the Introduction of the revised manuscript (p. 4, lines 66-69; p. 7, lines 137-142; & p. 8, lines 160-163). “Second, information presented about contingent responsiveness is incomplete. It seems that the authors captured base rates of responses, that is, frequencies of how many times parents responded to the different types of vocalizations. In work on contingent responsiveness, typically researchers would go a step further and conduct sequential analyses to gather probabilities of mother responding to infant vocalizations. Such probabilities account for base rates of behaviors, and can be used in analyses predicting language outcomes. These probabilities matter because they differentiate mothers who respond to an infant twice (but infants’ total vocalizations are 10) from a mother who responds to an infant twice (but infants’ total vocalizations are 3). The second mother is more responsive than the first. On line 305 the authors state that they are not seeking to detect causal effects of infants’ vocalizations, which is a slight mischaracterization of the baseman’s GSEQ method. They are probabilities, and they take into account all of the mother and infant talk. On page 29, the authors use the language “elicit” which appears causal anyhow. So my questions are: if authors are trying to extend prior literature into the home and see if patterns found in structured observations in lab (or home!) mirror, why not use established methods for contingent responsiveness?” We thank the reviewer for this suggestion and for pointing out the places where we have inadvertently somewhat misrepresented the prior literature and been sloppy in our use of terminology implying causal relationships! We agree that matching previous methodologies will indeed increase the generalizability about how behaviors observed in the lab translate to the naturalistic home environment. Past studies relating parent-infant interactions in more constrained settings to infant vocabulary and language outcomes have used a variety of different methodologies. Sometimes the focus has been on controlling for base rates and other times it has not, and when it has controlled for base rates, the methods used have varied. The models in the present paper controlled for the overall number of infant vocalizations and caregiver infant-directed utterances in Step 1 and for the overall number of infant canonical vocalizations and caregiver responses in Step 2, thus controlling for the base rates of infants’ vocalizations and caregivers’ responsiveness. We have added additional text in the revised manuscript to clarify how we controlled for the base rates of these vocal behaviors (p. 19, lines 409-410). We have edited the text in the Sequence Codes subsection of the Method section so that it no longer implies that sequential analyses (such as GSEQ) intend to detect causal relationships. We have also replaced the first instance of “elicit” in the Discussion section from the prior submission with a statement that implies less causality. We did, however, keep the term when discussing the potential feedback loop that we believe the results support—but we added mention that that feedback loop is “theoretical” (p. 30, lines 630-635). “Regardless, the authors should then also report how many infant vocalizations occurred in each segment that the mothers did not respond to to give readers a sense of the overall interaction. In the context of the home, unlike the structured context, mothers may attend to other tasks, and interactions may be fluid, comprised of smaller bouts perhaps. I would presume that mothers would have lower rates of responding to total number of infant vocalizations in the home than in the lab, where they have little else to do but interact, and my hypothesis would also be that bouts of very contingent interactions would focus on specific activities, like book sharing or play.” We agree with the reviewer that this would be useful descriptive information to present in the paper. We have now included the average rate in which caregivers contingently responded to infant speech-related vocalizations in the observed segments (p. 20, lines 435-436). Additionally, controlling for caregiver response rates in Step 1 in all of the models does not change the results. We have added this information in text (p. 18, lines 392) and have added the output for the models controlling for caregiver response rates to the SOM (see S12 & S13). Furthermore, we have added the number of infant vocalizations that did and did not receive contingent caregiver responses for each infant to the updated dataset on OSF. Additionally, we added a ZIP file that contains all of the timestamped excel exports from which these data were derived. Specifically, each export contains timestamped infant vocalization and caregiver response codes for each participant. This way researchers interested in probing these contingencies further have all of the data at their disposal to do so. “Finally, I appreciate that the authors noted the types of activities that occurred in the segments chosen, and I think that those should be highlighted. The study focuses on language interactions in the context of everyday life, and so interpretation of input in the context of play specifically (which comprised most segments it appears) is meaningful and necessary. It should also then be linked to prior work on language input by activity context, perhaps in the discussion.” The reviewer raises an excellent point that the contexts in which the interactions took place may have important implications of our findings. We have added further discussion of this point in the Future Directions section of the Discussion (p. 31, lines 666-670). Reviewer #2: “This is a well written manuscript that details the findings for in home parent-infant vocal interactions and their relation to language outcomes. This is an area of research that is underrepresented in the literature, as the majority of studies have been conducted in the lab. The meticulous coding captures specific responses (recasts, expansions) to more advanced infant vocalizations (canonical vocalizations) that support language development. The findings reveal important moment to moment vocal exchanges that can support positive outcomes. I appreciate the limitations discussed by the authors, but I would also suggest that there are potential applications of their research that they could elude to in the discussion. I agree that these are just short snippets of exchanges, but the importance of uncovering which specific vocalizations and feedback (loops) is significant for understanding how parents support language in day to day interactions.” We thank the reviewer for noting the importance of the current findings. The revised manuscript now includes additional potential applications of how the present results may inform caregiver practices that facilitate positive language outcomes in the home environment in the Discussion (p. 28, lines 586-588 & ps. 30-31, lines 642-656). Attachments Attachment Submitted filename: Response to Reviewers.docx https://doi.org/10.1371/journal.pone.0242232.r002
29 Oct 2020 Decision Letter - Iris Nomikou, Editor Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study PONE-D-20-19792R1 Dear Dr. Lopez, The reviewers and myself have now viewed the revision of the manuscript. 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. An invoice for payment will follow shortly after the formal acceptance. To ensure an efficient process, please log into Editorial Manager at http://www.editorialmanager.com/pone/, click the 'Update My Information' link at the top of the page, and double check that your user information is up-to-date. If you have any billing related questions, please contact our Author Billing department directly at authorbilling@plos.org. If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org. Kind regards, Iris Nomikou, Ph.D. Academic Editor PLOS ONE Additional Editor Comments (optional): 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: All comments have been addressed ******** 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 ****** 3. Has the statistical analysis been performed appropriately and rigorously? Reviewer #1: Yes ****** 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 ****** 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 ****** 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: It was a pleasure reading the revision of this manuscript. All of my questions have been addressed. I think the manuscript will make a valuable contribution to the literature on contingent responsiveness. ****** 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: Yes:** Yana Kuchirko https://doi.org/10.1371/journal.pone.0242232.r003
Formally Accepted
3 Nov 2020 Acceptance Letter - Iris Nomikou, Editor PONE-D-20-19792R1 Adult responses to infant prelinguistic vocalizations are associated with infant vocabulary: A home observation study Dear Dr. Lopez: I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department. If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org. If we can help with anything else, please email us at plosone@plos.org. Thank you for submitting your work to PLOS ONE and supporting open access. Kind regards, PLOS ONE Editorial Office Staff on behalf of Dr. Iris Nomikou Academic Editor PLOS ONE https://doi.org/10.1371/journal.pone.0242232.r004

Open letter on the publication of peer review reports

PLOS recognizes the benefits of transparency in the peer review process. Therefore, we enable the publication of all of the content of peer review and author responses alongside final, published articles. Reviewers remain anonymous, unless they choose to reveal their names.

We encourage other journals to join us in this initiative. We hope that our action inspires the community, including researchers, research funders, and research institutions, to recognize the benefits of published peer review reports for all parts of the research system.

Learn more at ASAPbio .