How to sell without words: What science knows about nonverbal behavior in personal sales and service

. In recent decades, a very modest number of papers on nonverbal behavior in sales and the service sector have affected the field of study. Nevertheless, a comprehensive conceptual model is missing. Very heterogenous views appear to shape the topic. Scholars have shown that empathy is a crucial factor in interpersonal interaction. In particular, this applies to salesperson-customer interaction. Additionally, researchers found that nonverbal behavior shapes 90 % of mutual understanding and verbal communication hardly has an influence. However , salespersons’ nonverbal behavior has received scant attention in marketing research. This study contributes to the corpus of knowledge by evaluating how the existent research is founded on various intellectual frameworks and by identifying the most important references, authors, themes, and journals, as well as comprehending it in a conceptual model of salespersons nonverbal behavior. To achieve this objective, I examined more than 3,000 publications published between 1994 and 2021 using bibliometric methods. This is a small body of literature compared to other fields. I determined four publishing eras that affected the evolution of research in this field. Nonverbal behavior has been studied from a range of angles in the publications that have published these articles. The predominant emphasis is on the United States and empathy as a central trait, offering scholars the ability to conduct further cross-national and cross-industry research. My study not only provides intellectual and social frameworks, but integrates them in a conceptual model. Thus, it lays the foundation for future study.


Introduction
Nonverbal behavior in the context of personal sales and service has received scant attention thus far.Nonetheless, its primacy in personal sales cannot be disputed.Especially, given the fact that "mutual understanding or empathy is more than 90 % dependent on nonverbal exchange and not on the content of verbal communication" (Trautmann-Voigt & Voigt, 2012), the importance of nonverbal behavior for personal sales is immense.Looking at detailed facets, I want to emphasize three aspects that underline the impact of nonverbal behavior in dyadic interaction in the business context.Firstly, nonverbal behavior is a key success factor for employees who interact with customers, because it facilitates emotional exchange and consumer decisions contain a huge affective component (Weißhaar & Huber, 2016).This is because empathy is largely based on nonverbal behavior (Feniger-Schaal et al., 2021).It is often referred to as emotional contagion (Hasford et al., 2015).Secondly, appearance and physical attractivity tremendously affect social interaction.That is known as the "what is beautiful is good" -stereotype (Dion et al., 1972).Caused by this social perception, physically attractive employees get promoted more often (Agthe et al., 2011), get more raise (Frieze et al., 1991), and are perceived as more amiable, humorous, intelligent, and socially skilled (Feingold, 1992).Thirdly, nonverbal behavior of salespeople significantly affects customers' perception of the sale.Lin and Lin (2017) demonstrated that employee nonverbal communication has a favorable effect on customer pleasant sentiments and customer-employee rapport while Pauser et al. (2018) found that specific arm actions, arm postures, and action functions have a substantial effect on a salesperson's charismatic look, eliciting favorable sentiments toward the salesperson.In line with Ferdinand and Wahyuningsih (2018), this supports the knowledge exchange between customers and salespeople.Especially with more self-service technologies for customers arising, the importance of a high service quality in dyadic interaction is to be underlined as the role of sales is emerging to customer co -creation behavior (Delpechitre et al., 2018;Grigorescu et al., 2019;Hossain et al., 2019).
Therefore, it is no question that the role of nonverbal behavior is important for personal sales.Nevertheless, research is scarce and scattered -even though intuitively most people might assume that there is a broad body of research, because the nonverbal behavior in sales is broadly considered important.This is even underlined by a tremendous amount of practitioners' literature.A search on www.amazon.comfor the words "nonverbal sales" reveals more than 2,000 results in the category books with titles such as "Body Language How to Read Any Body [sic]: The Secret to Nonverbal Communication to Understand & Influence In, Business, Sales, Online, Presenting & Public Speaking, Healthcare, Attraction & Seduction" (Borthwick, 2021).
So, there seems to be a gap between the amount of practitioners literature and scientifically founded literature such as journal articles.To express it colloquial: There seems to be only very little scientifically backed literature on nonverbal behavior in sales, but people cannot believe it, because there is so much practitioners literature and the topic is of such great intuitive importance.I formalize this problem in a research questions: RQ: What is the knowledge base of nonverbal salesperson behavior, researchers and practitioners can trust?
I answer this research question through an examination of material published in leading journals using bibliometric techniques.I choose bibliometric analysis because it offers an approach that is quantitative and reproducible.Because of its very transparent and objective procedure, I chose it over more qualitative approaches to literature review.The approach I chose can be compared to the form of a diamond.I opened up a very specific field of knowledge and integrated a huge amount of papers (over 3,000) and then narrowed it down to only very few relevant papers that shape the conceptual model.Thus, I could get to "proving what is not there" as close as possible.
Consequently, my contribution highlights the most prolific authors, the theoretical foundations, the previously addressed topics, and, consequently, new avenues and opportunities for future research.Additionally, my study offers as a quantitatively supported beginning point for performing literature reviews in subsequent studies addressing the topic and serves as a foundation for doing meta-analyses.For practitioners, it offers a single point of knowledge to familiarize with the topic and to hold against practitioners literature and what is offered in trainings.Thus, they can assess the reliability of trainings to their salesforce and the literature on nonverbal behavior in sales.
Firstly, I review literature on nonverbal behavior.This section is to provide a general understanding of the concept, while the actual structured review of the literature with bibliometric techniques follows in the main part of this paper.Secondly, I describe the approaches employed to analyze the intellectual structure of research on the issue under consideration.Thirdly, I provide the results obtained from the study and discuss them.Fourthly, and finally, I summarize my findings and make recommendations for future research.

Literature review
Nonverbal behavior is at the center of interaction between people.Trautmann-Voigt and Voigt (2012) assume that 90 % of mutual understanding is based on the non-verbal level.To begin with, it is necessary to distinguish between nonverbal communication and nonverbal behavior.According to Argyle (2013), the primary criterion is a signal's intentionality.Nonverbal communication occurs when a human being actively delivers a signal through one of the routes: Facial expression, gaze behavior, pupil dilation, gestures, body movements, posture, body contact, spatial behavior (proxemics), clothing, general appearance, nonverbal vocalizations (vocal utterances), and smell.
Unintentionally transmitting a signal through one of the channels is classified as nonverbal behavior (Argyle, 2013).Thus, nonverbal behavior is any nonlinguistic behavior (Depaulo & Friedman, 2010).But this definition includes activities like driving a car or strolling a dog.This may lead to confusion over the term nonverbal behavior.In response, Ambady and Weisbuch (2010) adapted the definition to "nonverbal behavior can be defined as perceptible non -linguistic behavior that is not instrumental to manipulating the physical state of the world."(Ambady & Weisbuch, 2010, p. 2).This definition excludes non-social object manipulation, which is more in line with what social psychologists refer to when studying nonverbal behavior.
"Encoding" (creation and transmission of nonverbal behavior) and "decoding" (detection and interpretation of nonverbal behavior) have been used to distinguish transmitter and receiver of nonverbal signals (Argyle, 2013).Despite this, Ambady and Weisbuch (2010) argue that encoding and decoding are not conscious actions.
In social psychology, the production of nonverbal signals is explained by theories of nonverbal leakage and theories of nonverbal influence.
Theories of nonverbal leakage are mostly inspired by the findings of Charles Darwin.The primary principle of them is that nonverbal behavior reveals emotion (Darwin, 1872).Darwin identified numerous parallels and distinctions between human beings and animals in terms of nonverbal behavior.Paul Ekman, Sylvan Tomkins, and Caroll Izard extended Dar-win's ideas by relating subcortical brain regions to emotional expression patterns (Paul Ekman, 1973;P. Ekman & Friesen, 1969).Elfenbein and Ambady (2002) conducted a metaanalysis of these theories of universality in facial emotion.Only 3 % of cross-cultural samples recognized one emotion at a rate greater than chance.Thus, it may be asserted that specific emotions are hardwired to related facial expressions.
Theories of nonverbal influence not only consider the display of emotion but also aspects of social influence and communication.As with theories of nonverbal leakage, theories of nonverbal influence use an evolutionary perspective, but they go even further in implying that all kinds of nonverbal communication serve the expresser's interests first and foremost.Emotional expression is incorporated into this section.Nonverbal influence theories assert that nonverbal expressions have an effect on conspecifics' actions (Ambady & Weisbuch, 2010).Nonverbal impact theories assert that messages that have no effect on others cannot contribute to survival and reproduction.No one-to-one relationship is made between inner states and nonverbal behavior in models of nonverbal influence, because it could even be damaging to a sender if the receiver could always read the sender's inner state.

Unit of analysis
Bibliometric analysis is a quantitative examination of bibliographic elements.I chose to use journal papers because they are regarded as "certified knowledge" and, moreover, because they are the product of an evaluation procedure, the findings are considered reliable.(A.-R.Ramos-Rodríguez & Ruíz-Navarro, 2004).Therefore, I omitted proceedings papers, news stories, and other database-supported document types.
I analyzed citations and co-occurrences of citations.Citation analysis is based on the weight given to a publication by scholars when citing it as a source.As a result, it may be stated that the more frequently an article is mentioned, the more influential it will prove to be in terms of advancing the research community in a particular field (A.R. Ramos-Rodríguez & Ruiz-Navarro, 2008).

Sourcing and administration of databases
I gathered article information from journals archived in Clarivate Analytics Web of Science (Clarivate Analytics, 2022).Web of Science is a multidisciplinary electronic database providing bibliographic metadata from peer-reviewed papers since 1945.It covers 1.9 billion cited references from over 171 million records and 18,000 journals and a broad band of different disciplines (Clarivate Analytics, 2022).WoS is "an indispensable citation database" (Meho & Yang, 2007, p. 2123).Therefore, it promises the most results compared to other databases.I employed an established, extensive search strategy.Plusquellec and Denault (2021)  This provided me a dataset of 3,084 articles.At first sight, the sample might appear to be overblown, but I decided to include rather too many than too few papers in my qualitative checking process.Thus, I made sure to not exclude papers involuntary due to avoiding manual effort.After continuous verification processes, I eliminated articles that are not related to the field.Those were mainly from the fields of medicine and computer science.In a qualitative approach, I eliminated irrelevant data iteratively and set the minimum number of citations to three.Therefore, I ensured that newer research will be considered and that the dataset is not biased to a historical perspective.The acquired papers were published until 2021.I viewed each article as a potential field-enhancing contribution.Once the dataset had been generated, I exported the data and imported it to bibliometrix, an R-tool for bibliometric analysis (Aria & Cuccurullo, 2017).I used R as a 64 bit Version on Windows in Version 4.1.0.and combined it with R studio and activated the package biblioshiny for bibliometrix.Biblioshiny offers the whole process of bibliometric analysis in one software.

Indicators and results of visualization
I chose descriptive and relational bibliometric indicators and techniques for this investigation.Languages, countries, and institutions all contribute to an explanation of the sociodemographic situation.The publication year frequency aids in visualizing and establishing stages in the history of this subject's research.Keywords facilitate comprehension of the authors' self-evaluation of how concepts and studies are categorized and connected in this context; this reveals which of these concepts have not been well analyzed.The principal contributors and journals show who did the majority of the study and whose journals housed the majority of the studies.The co-occurrence of authors establishes the structure of research communities, and the co-occurrence of citations aids in the comprehension of the intellectual framework.Finally, maps help visualize what has been accomplished, the communities engaged, and also point to potential areas of future investigation.

Data analysis process
Before extracting and cleaning the data, I established the selection criteria for keywords, years, target indexes, and the selected database.I processed the collected data to develop uniform criteria for achieving the intended objective.Data cleaning included capitalization normalization, author initials checking, duplication removal in cited references, and data completion.Typically, this is achieved using an iterative method until the researcher has the proper data registers, which are subsequently analyzed and cleaned.The analysis is then conducted using the indicators and maps indicated previously to acquire the results.Following that, some concluding remarks and conclusions are made in light of the findings.At the conclusion of the process, limitations and areas for future investigation are mentioned.

Results and discussion
I used the selection criteria to do a search of the Web of Science main collection database, completed the data preparation activities outlined above, and retrieved 234 articles.Thus, I could narrow down a broad variety of papers two few relevant ones that can be considered as a knowledge base that researchers and practitioners can trust.In the following chapters I present the structure of that knowledge base, so researchers and practitioners can easily understand connections between different research streams.

Publications per year
The articles I analyzed were published between 1994 and 2021.As Figure 1 shows, different periods can be seen, which I established for better analysis and discussion.There is a first period, between 1994 and 1999, during which only a few publications are produced, reflecting the customary seminal timeframe.Between 2000 and 2009, the second period, the average number of papers arises by up to thirteen times.The number of publications increases continuously to a maximum of thirteen publications in the final year of this period.Even while the third period, from 2010 to 2016, indicates the first reduction in publishing activity and, consequently, volatility, it still demonstrates a significant growth in the number of articles and a stable baseline of over 11 per year on average.This is a clear indicator that the scientific area has advanced to a new phase.2017 to 2021, with 89 articles, were the years in which the greatest number of papers were published during this time.The growth in published articles suggests that the subject is developing.
As a result, I see that as indication that the topic receives rising attention, and researchers consider it as important.This is especially interesting, as digitalization is emerging and business models all over the world are disrupted by the use of digital technology.Hence, I would have as well considered it plausible if research on nonverbal behavior in sales would be decreasing, because personal interaction in sales and service might lose importance as it might be replaced by digital tools and services.But the contrary is the case, a nd the topic gains importance despite the increase in digital services.Resultingly, I see the rising research as an indication that personal interaction in sales and service even gains importance.

Countries of publications
Despite contributions from 70 countries, more than half of the writers are from the United States, the United Kingdom, China, and Australia, representing a variety of institutions.Figure 2 illustrates the writers' nationalities as well as their closeness to the other collaborators.They were more cooperative the closer they were.It pinpoints geographic and cultural groups surrounding the United States, Australia, Germany, and Turkey.Additionally, two more isolated cooperations between Finland and Italy, as well as New Zealand and Ireland are portrayed.According to my assessment, the large concentration of publications by country has two repercussions.First, it contributes to the development of more in-depth study subjects; second, it creates a chance for new countries to collaborate; in other words, to collaborate with other researchers and institutions on these subjects.

Journal productivity
Although the publications appeared in 127 journals, only 23 of them represented more than 48 % of the total.Table 1 lists the twenty most influential journals and the number of papers they published, as well as the h-index I calculated for them, their total citations, and their date of establishment (Hirsch, 2005).As is the case in other fields, the oldest and more topic-specific journals are placed highest, with the exception of the highest-ranked journal.The Journal of retailing and consumer services has published 11 articles containing a total of 448 citations since 2005.The next journal is Psychology & marketing, which published 9 papers, followed by Journal of business research, which published eight, Service industries journal, which published eight, and European journal of marketing, which published six articles.The h-index indicator helps these journals strengthen their ranking position.Other journals, by their very nature, embrace many points of view and hence present a range of perspectives in the arena.This is particularly true for studies published in journals such as the International journal of contemporary hospitality management.Developed themes permit the combining of a fundamental collection of journals that are largely focused on the major subject (such as business management, or psychology) with another group that takes a different perspective to the issue.The map in Figure 3 assists in visualizing these journal findings and their categorization.Co-citation analysis of journals enabled me to create a map of their proximity and relationship, as well as to highlight the locations of the articles that shape the body of knowledge.Due to their high publishing and citation counts, journals in the fields of marketing and psychology are primarily clustered in the map's center.This select group is related to several journals, including business management and business research, and specialty journals circle surrounding it.The proximity represents how they are referenced together, i.e., how publications highlight important information pillars for their research.It thus allows me to see the primary data that go further into the topic and serves as a point of reference for several perspectives.
Grewal's studies, which are firmly anchored in marketing, investigate subjects such as embodied variables for the usage of portable scanners in B2C sales, employees digital presence on a website or customers' facial expressions.Karatepe deals with the measurement of service quality in different contexts.Söderlund focuses on Grewals counterpart and takes into account the facial expressions of service workers.Agnihotri's work embodies a psychological perspective on salespeople.He analyzes both interpersonal traits of salespeople as well their interpersonal mentalizing skills.Therefore, empathy is taken into account.The articles published by Bagozzi dive deep into the understanding of empathy for goal-oriented behavior as well as fear in the context of cold calling.It should be noted that a high score in this section reflects the amount of effort invested in the matter and is not always correlated with the subject's importance in the literature.This topic is covered in further depth later in the chapter by utilizing cited references.

Study of references
In add to an investigation of authors, a study of the references used by writers in their articles helps to construct the intellectual map of the subject.575 references are included in my sample.I present the seven most cited ones, because starting with the eighth there follow 24 studies that are cited 2 times and 544 studies that are cited one time.I decided not to present them.The most cited study by Aggarwal et al. (2005) was referred to in 11 articles.The study contributes by providing a conceptual model that connects salesperson empathy and listening abilities to three outcome factors.The authors used structural equation modeling to test their concept using responses from a postal survey of 162 buyers from a variety of corporate groups.The model indicates a high positive link between empathy and the following variables: salesperson listening, salesperson trust, and salesperson satisfaction.Additionally, listening is associated with a buyer's trust in and happiness with the salesperson, but not with expectations for future interactions.Future interaction expectations were positively related to trust in and satisfaction with the salesperson.
The second most cited works are those of Aaker (1991), Agnihotri and Krush (2015), Allport et al. (1954), E. W. Anderson (1998), E. W. Anderson et al. (1994) and J. C. Anderson and Gerbing (1988).They are equally cited three times.Aaker (1991) gives a clear structure for the link between a brand and its symbol and slogan, as well as each of the five underlying assets, which will help managers understand exactly how brand equity contributes value.
Agnihotri and Krush (2015) created a paradigm of ethics based on the person-situation interaction perspective.They examined the influence of a critical social emotion, empathy, on ethical behaviors, as well as the effect of a critical situational factor, trust in one's sales manager.Additionally, they investigated the moderating effect of a salesperson's trust in their management on the relationship between empathy and ethical behavior.Moreover, they investigated the effect of a salesperson's ethical behavior on their performance.They validated their model using SEM analysis on dyadic data acquired from salespeople and their respective managers.The findings corroborate the direct effect of empathy on ethical behavior and also emphasize the interaction between trust and empathy on ethical behavior.Allport et al. (1954) have sought to convey the literature on group bias in a comprehensible format.Their book is grouped around eight major themes: preferential thinking, group differences, perceiving and thinking about group differences, sociocultural influences, acquiring prejudice, prejudice dynamics, character structure, and resolving group tensions.E. W. Anderson et al. (1994) asked if there is a business case for increasing customer satisfaction.They investigate the nature and degree of the connection between customer satisfaction and economic returns.They explain how expectations, quality, and price should affect customer happiness and profitability.Their findings indicate that quality has a favorable effect on customer satisfaction and, consequently, profitability.The authors demonstrate the economic benefits of improving customer satisfaction through the use of an empirical forecast and an analytical model.Furthermore, they examine why expanding market share may result in decreased consumer satisfaction and provide preliminary empirical support for this notion.
E. W. Anderson (1998) also provides the next study, where he asks "Do dissatisfied customers engage in more or less word of mouth than satisfied customers?"Both possibilities have theoretical and empirical validity.He constructed a utility-based model of the relationship between customer happiness and word of mouth in order to gain a better understanding of this topic.On the basis of evidence from the United States and Sweden, the hypothesized functional form-an asymmetric U-shape-cannot be dismissed.Furthermore, the estimation findings for the two samples are comparable, implying that the postulated link is generalizable.Additionally, his findings reveal that, while unsatisfied consumers do engage in more word-of-mouth than satisfied customers, popular assumptions about the magnitude of this difference tend to be overblown.
Finally, he as well provides the last here mentioned study.This is a methodical paper where J. C. Anderson and Gerbing (1988) elaborate structural equation modeling in practice.In terms of co-citation analysis for the cited references, I studied publications in order to identify the intellectual framework that underpins the topic's research.A co-citation map (Figure 4) assists in visualizing the findings.I used the Louvain algorithm to run a cluster analysis on a set of 70 nodes with a repulsion force of 1.This allowed me to view the articles as the axes that form the literature's focus.The analysis shows three main clusters and nine smaller clusters pivoting around them.
The main and central cluster is built around the works of Aggarwal et al. (2005).J. C. Anderson and Gerbing (1988), Agnihotri and Krush (2015), Ambady et al. (2006), Ahearne et al. (2007), Aldlaigan and Buttle (2002), Abbasi and Alvi (2013) and Alavi et al. (2016).It is displayed in red in Figure 4. Ambady et al. (2006) add value to the cluster by analyzing "thin-slices" of salespeople and let customers evaluate those short videoclips.The authors show that the observability of the rated variable plays a critical role in determining the criterion validity of thin slice assessments.Ahearne et al. (2007) establish a collection of behaviors referred to as "salesperson service behaviors" on the basis of extensive exploratory interviews across professional selling domains.The authors illustrate the influence of these actions on customer satisfaction and trust, as well as on an objective measure of the customer share of market, using data from 358 customers.The authors construct a competitive model that is unusual in that it incorporates consumer feedback about rival salespeople.The findings suggest that these salesperson service practices are critical for establishing confidence and increasing customer satisfaction, which results in increased market share for customers.Aldlaigan and Buttle (2002) presented a new scale for assessing retail bank customers' views of service quality.They designed and validated a new 21-item scale that measures four elements of service quality: service system quality, behavioral service quality, service transactional accuracy, and machine service quality.The authors propose that customers evaluate service quality on two levels: organizational and transactional.Alavi et al. (2016) focus on discount discussions that are common in retail and are a critical tools for tailoring retail prices to each individual consumer.The authors analyze a four-source multilevel data set pertaining to 537 salesperson-customer interactions in the B2C vehicle selling setting.The results demonstrate that salespeople may significantly lower the discounts they provide to consumers by using precise customer price importance sensing.Additionally, studies indicate that retail salespeople misperceive customer price importance due to their reliance on heuristic consumer signals.
The second cluster is connected to the central cluster and contains the works of Aaker (1991); Ambady and Rosenthal (1993), Aaker (1996), Ajzen and Fishbein (1980), Alrubaiee and Al-Nazer (2010), Ambady et al. (1996) and Aaker and Joachimsthaler (2000).Ambady and Rosenthal (1993) assessed the accuracy of strangers' consensual personality judgements based on "thin slices" of targets' nonverbal behavior in respect to an ecologically valid criteria variable in three studies.Consensual perceptions of college professors' molar nonverbal behavior based on extremely brief (less than 30 s) silent video clips were found to strongly predict global end-of-semester student ratings of teachers in the first research.In the second research, the authors used comparable judgements to predict how a principal would rate high school instructors.The third investigation discovered a high correlation between assessments of even smaller slices (6-s and 15-s clips) and the criteria variables.Specific micro nonverbal actions and physical appearance assessments of instructors were not as highly associated to the criterion variable.Ajzen and Fishbein (1980) focus on understanding attitudes and the prediction of social behaviors.Therefore, they not only focus on theoretical points of attitudes and behavior, but also on how to define and measure them.Moreover, they take into account how to predict behavior from intentions and determinants of behavioral intentions.
Alrubaiee and Al-Nazer (2010) investigate the impact of relationship marketing orientation on customer loyalty.According to the authors, in today's highly competitive and globalized banking environment, establishing customer loyalty is a major marketing problem.Increasing sales and consumer share, decreasing costs, and increasing pricing may all be achieved by cultivating loyal customers.Therefore, they highlight the importance of relationship marketing as a strategic strategy for increasing client loyalty, competitiveness, and satisfaction.Their goal is to scientifically examine the influence of relationship marketing on client loyalty.They examined how demographics and relationship marketing factors affect consumer loyalty.The authors used a sample of 450 bank customers in Amman, Jordan, who were given standardized questionnaires in 2008.Regression analysis shows that the relationship marketing approach explains consumer loyalty variance.Also, sex and money had a considerable influence on the marketing-loyalty connection.The findings help to clarify the links between relationship marketing orientation, customer loyalty, and demographic characteristics.Ambady et al. (1996) in their article assess politeness behaviors in Korea and the U.S..By examining the nonlinguistic features of politeness in two cultures, their research contributes to the validity of politeness theory (Brown & Levinson, 1987).Politeness strategies were examined across a variety of communication channels.The authors discovered that politeness strategies were communicated non-linguistically as well as linguistically, and that nonlinguistic strategy use was related to social and contextual factors.Two studies found that Koreans' politeness techniques were more impacted by relational signals, whereas Americans' politeness methods were more influenced by the message's substance.Their study was the first of its kind to investigate the nonlinguistic communication of politeness across cultures.
The third cluster is built on the works of Fishbein and Ajzen (1975) and creates a single line continuing from those works.E. W. Anderson (1998), Ahmed et al. (2010), Al-Hawari andWard (2006) and one anonymous study built on this work.Fishbein and Ajzen (1975) have two goals: First, to present a complete overview of a broad spectrum of the theoretical and empirical literature on attitudinal phenomena; a nd second, to demonstrate that this material can be merged into a coherent and systematic explanatory structure.
I have already presented the results of E. W. Anderson (1998) in the analysis of references.Ahmed et al. (2010) focus on the impact of service quality on customers' satisfaction.They provide empirical evidence from the telecom sector of Pakistan.
Al-Hawari and Ward (2006) aimed to examine the link between customer impression of service quality and bank financial performance in Australia's new automated banking system.In addition, they wished to examine the function of customer satisfaction in moderating this link.The writers propose a mediated model that links service quality to banks' financial performance via customer satisfaction within the context of automated retail banking, and test it using structural equation modelling.Their findings show that customer happiness mediates the association between automated service quality and financial success.
Different smaller clusters are pivoting around those three central clusters.

Topics of nonverbal salesperson behavior
The authors in my paper used 101 different keywords to classify their topics.Figure 5 visualizes which keywords are mentioned together in the form of a co-occurrence map.The magnitude of each node on the map indicates the significance of every word.The proximity of words and lines reflects the degree of their connection.As one of the criteria for selection, the term "empathy" yields the predicted results.Additionally, "service quality" and "customer satisfaction" prove relevant for the research objective as study topics.This is also consistent with identified intellectual frameworks, the most relevant authors, and the listed references on nonverbal behavior in sales and service.This applies as well for the clusters built, as they represent the research streams discovered before.The cluster in blue represents the stream on personal selling, the one in yellow on trust and communication, the one in red on customer satisfaction and service quality, the one in purple on consumer behavior and consumer psychology, the one in green on empathy in service and frontline work, and the one in brown on facial expressions and emotion.Moreover, some focuses on countries and industries can be identified.

Figure 5. Co-occurrence map of authors' keywords
Source: Author's own research.

Conceptual Model
Based on the bibliometric analysis, I integrated the results in a conceptual model that brings together the most relevant intellectual frameworks and builds a basis for further research on nonverbal behavior in sales and service.Thus, I answer the research question and present the knowledge base, researchers and practitioners can trust.At the same time, I link it to the studies that back up the model and hence provide touchpoints for further research.
The model is focused on dyadic interactions in face-to-face setting of either sales or service, while sales can be viewed as specific form as a service applying the uno-actu-principle (Meyer et al., 2016).This means that a service is produced and offered simultaneously.The model contributes to the literature by providing an integrated perspective of the most relevant works on nonverbal behavior in sales and service with those works being identified in a systematic and empirical way.The model is displayed in Figure 6.As dependent variables the model picks up sales outcomes, trust in the salesperson, satisfaction with the salesperson and customer loyalty.As independent variables I identified cognitive and affective processes of the consumer, salesperson physical attractiveness, empathy, sales performance, salesperson expressiveness, service behaviors, confidence, positive expressions, nonverbal immediacy and reliability.The model proposes customer satisfaction as a mediator variable between empathy, sales performance, reliability and customer loyalty and sales outcomes.As well it considers both salesperson listening and trust in the salesperson as a mediator between empathy and satisfaction with the salesperson.Additionally, I expect satisfaction with the salesperson to be a mediator between salesperson listening and customer satisfaction.
Because a map at a scale of 1:1 would not offer any added value, I have simplified the present model and partially combined variables found in the literature and adapted the nomenclature accordingly.
From Grewal et al. (2020) I integrated their perspective on cognitive and affective processes.Even though they expected an influence from cognitive processes on affective experiences, I included both variables as influencers on sales outcomes in a broader sense.
From Karatepe (2011), I included empathy and reliability as independent variables.The variables sales performance, especially relationship performance and salesperson service behaviors express interaction quality.The service environment is excluded to lay the focus of the model on dyadic dimensions.I integrated customer satisfaction and customer loyalty with their relationship as dependent variables into the model.This is backed by works of Karatepe et al. (2005), Abbasi and Alvi (2013)and Johns et al. (2004).Berg et al. (2015) brought the independent variable positive expressions, e.g., smiling into the model.Moreover, I integrate salesperson expressiveness and nonverbal immediacy into the model.Thus, the model conceptualizes that salesperson's emotions affect customers based on the theory of emotional contagion.
From Agnihotri and Krush (2015) I integrate the variables empathy and sales performance into the model.Even though Agnihotri et al. (2017) focus on salesperson's internal mentalizing (i.e.rapport building, detecting nonverbal cues, taking a bird's-eye view, shaping the interactions) I decided not to integrate it as a different variable, as it is mainly covered by cognitive and affective empathy, and in this way I could reduce the complexity of the model.With the focus on sensing how important prices are for customers, empathy can be seen as backed up by Alavi et al. (2016) even though they measure customer price importance (CPI) sensing.Research of Bagozzi (Soscia et al., 2018;Verbeke & Bagozzi, 2000), Agnihotri and Krush (2015) and Aggarwal et al. (2005) emphasizes the importance of empathy for sales, especially when drawing the connection between empathy and sales or customer orientation (Bagozzi et al., 2012).Aggarwal et al. (2005) extend the model by the variables salesperson, listening, trust in the salesperson and satisfaction with the salesperson with their displayed relationships.E. W. Anderson (1998) and E. W. Anderson et al. (1994) back up the connection between customers satisfaction and sales outcomes as they investigate customer satisfaction as a business case.
Salesperson Service Behaviors are based on the research of Ahearne et al. (2007) as well as their impact on customer satisfaction and therefore integrated in the model.
Comparing the model to the investigated keywords in the literature, we see parallels.This strengthens the validity of the conceptual model.

Conclusions
This study reveals that nonverbal behavior in sales and service is a very impactful yet complex topic in the literature of business and management.Examination of the articles produced between 1994 and 2021 suggests that there have been four phases of study on this topic: a time of planting from 1994 to 1999, a period of rapid growth from 2000 to 2009, a period of volatility from 2010 to 2016, and a period of development beginning in 2017.This structure is characteristic of research on a topic or field that is undergoing development.As a result, I conclude that the topic receives rising awareness, even though one might expect that this might not be the case, because digital services gain importance.In the same time, those services substitute seller-consumer interaction.Nevertheless, nonverbal behavior in sales receives rising research attention.I interpret this as a sign that the quality in consumer-seller interactions must increase in return, so that it continues to have a right to exist in relation to digital sales processes and generates added value for customers.Whenever a topic has reached a stage where it may be deemed settled, intellectual foundations provide a platform for doing thorough investigation on unforeseen related concerns I believe that the concentration of published papers by U.S.-based authors has contributed to a deeper understanding of the issue, while also pointing to potential international research collaboration avenues.This sort of joint effort may result in enriched outputs and novel perspectives that are rarely addressed in a single geographic region.To further point it out: collaborations between countries could provide a chance to investigate cultural specifications.For example, I could not find works that concentrate on the German-speaking market.Nevertheless, I assume there might be cultural differences in salesperson's nonverbal behavior compared to other western nations such as the U.S. let alone Asia, which follows a different cultural code.
The bulk of publications are journals with marketing or social psychology as their primary objective.Nonetheless, there are over a hundred sources giving a variety of viewpoints.Publications from several disciplines, including service management, organizational behavior, psychology, strategy, and management in general, can therefore provide a multidisciplinary view on the issue at hand.
According to my research, the most prolific authors handled the problem from several angles that were consistent with earlier findings.Grewal largely provides a perspective from the stance of marketing, Karatepe undertakes research from the perspective of service quality, Söderlund concentrates on facial expressions, Agnithori on psychology in sales, Bagozzi embodies the standpoint of empathy, and so on.Some writers published their research in the service field, which is compatible with the availability of specialized publications in this subject.
Assessment of the keywords authors use to identify their publications reveals strong ties to psychological concepts, a constant pursuit of the relationship between performance, service quality, customer satisfaction, customer loyalty, and emotions, and a lack of depth in the majority of industries studied.These keywords describe the fundamental organization of the cited sources' findings.This homogeneity suggests that the topic's study was constructed appropriately during the era of development.
Articles by Aggarwal, Aaker, Agnithori, Ambady, and Ajzen constitute the conceptual foundation of nonverbal behavior in sales and service within the analyzed time frame.Their research aids in establishing a foundation of cited references based on these methodologies, studying themes such as the relationship between empathy and listening skills, brand management, and psychological principles governing consumer behavior.The cited references demonstrate that this topic's study is organized around studies that highlight psychological perspective methods.Additionally, nonverbal behavior emerges as an important idea for grounding and related research.These conclusions are corroborated by the outcomes of the component analysis.Components exhibit a great desire to illustrate the relationship between nonverbal behavior and performance for the purpose of acquiring a competitive edge.In this spirit, empathy emerges as one of the key characteristics that may influence performance outcomes, showing that its contribution aligns well with the favorable impact of investing in well-selected frontline workers.Accordingly, it seems sense that there are several references that provide an intellectual foundation for the previously mentioned concept.
This extensive body of research, examined from a range of viewpoints, such as the personality variables that influence nonverbal behavior, has successfully explained the positive relationship between nonverbal behavior and performance.Regardless of this, I discovered that other techniques, such as the relationship between self-monitoring, expressiveness, and nonverbal immediacy and sales effectiveness, customer orientation, and work happiness, have significant space for future growth.
It is noticeable that the body of literature contains mostly variables of nonverbal behavior displaying personality traits that influence nonverbal cues or are displayed by them.
The questions arises, if researchers consider them as the more important variables to measure or that they offer more value in researching nonverbal behavior due to methodical issues.Especially in the field of b2b sales and service, it is a challenge for scholars to gather data on real situations.The simple presence of a recording setting might influence the interaction and, therefore, bias the process, even though Pauser and Wagner (2019) offer promising new opportunities using sensor technology.Nevertheless, if salespeople can report self-assessments via a scale, scholar can get access to a broader and more representative sample.Anyway, self-reporting scales are not free of risks.For example, common method bias needs to be checked for (Simmering et al., 2015).
The results from the different intellectual frameworks build a conceptual model that summarizes the current state of knowledge on nonverbal behavior in sales and service.Additionally, the results from the analysis of keywords point in the same direction and therefore strengthen the model.Thus, this model provides a trustworthy knowledge base for researchers and practitioners and summarizes what science knows about nonverbal behavior in personal sales and service.Moreover, it offers a starting point for diving deeper into the topic at hand, because the most relevant studies are aligned and put into a coherent model.With regard to my initially stated problem and resulting research question, I want to state that practitioners literature is not necessarily untrustworthy or even wrong.But it is often based on subjective perceptions of single salespeople or sales coaches.Those perspectives can be very helpful with a high practical relevance.Yet, they are not backed by scientific methods.Moreover, there is no process like a peer-review for practitioners literature in order to ensure quality.
My research has some limitations.Although I assessed contributions over the life of the study, it may be advantageous to undertake the same type of analysis at each of the stages stated.This may provide a new perspective on the evolution of data and a novel method for understanding prospective patterns.
Future research on nonverbal behavior may seek to fill up some of the gaps I have identified.It would be fascinating to obtain a deeper understanding of a larger range of sectors and to do more international studies.Moreover, it would be beneficial to firstly gain insights in salespeople and customer perspectives on the conceptual model to understand causalities and, secondly, empirically test the model.For this purpose, I recommend three different approaches to further investigate the research problem.Firstly, with a qualitative approach, researchers could generate further insights in the perceptions and worlds of thoughts of salespeople.Moreover, methodologies from psychotherapy, especially bodywork therapy and embodiment, offer promising chances to operationalize nonverbal behavior of salespeople qualitatively.This could be used to analyze video data.Secondly, case studies in the industry and experiments, such as role plays, could help to provide insights with a strong relation to practice.Thirdly, with quantitative analyses, researchers could test hypothesis that can be generated from the literature research.
Additionally, my work gives a solid platform for doing meta-analyses on this issue.

Figure 1 .
Figure 1.Articles on nonverbal behavior in sales and service per yearSource: Author's own research.

Figure 3 .
Figure 3. Co-citation analysis of journals

Figure 4 .
Figure 4. Co-Citation Map of Papers

Table 1 .
Journals with publications on nonverbal behavior in sales

Table 2 .
Most prolific authors