Cross-Cultural Adaptation of the Brief Form of the Interpersonal Competence Questionnaire (ICQ-15) into Japanese

Abstract

(1) Background: This study aimed to translate and develop a culturally adapted Japanese version of the brief form of the Interpersonal Competence Questionnaire (ICQ-15) and to evaluate its psychometric properties for Japanese adults. (2) Methods: In the pilot test, we asked five Japanese university students to rate their understanding. Then, a final sample of 428 adults between 18 and 40 years old (45.1%male and 54.0% female) completed the Japanese version of the ICQ-15. To examine the psychometric properties of the ICQ-15, item analyses, confirmatory factor analysis, internal consistency analyses, and convergent and divergent validity analysis were performed. (3) Results: Although the items did not follow a normal distribution, most of them showed a good homogeneity index, suggesting good internal consistency between the items. The confirmatory factor analysis showed that the five-factor model had acceptable fit indices. Spearman correlations between the ICQ-15 and the Communication Skills Questionnaire (CSQ) supported its convergent validity, while correlations between the ICQ-15 and the Patient Health Questionnaire-9 (PHQ-9) supported its divergent validity. (4) Discussion and conclusions: A Japanese version of the ICQ-15 was developed showing good psychometric properties to be used to assess interpersonal competence in adults. This questionnaire demonstrated satisfactory internal consistency reliability among Japanese adults. A future study will investigate the criterion-related validity and temporal stability of the scale.

1. Introduction

According to Bochner & Kelly [1], interpersonal competence refers to an individual’s ability to effectively interact with others in different social contexts, including the ability to communicate clearly and effectively, understand the emotions and perspectives of others, resolve conflicts constructively, collaborate with others jointly, and establish healthy and meaningful interpersonal relationships. This competence entails a combination of social, emotional, and communicative skills, modulated by sociocultural (ex.: religion, values, traditions, or language) and environmental factors (ex.: education, family, technology, or globalization).

Canary, Cupach, and Serpe [2] specifically explored the role of competence in interpersonal conflict over time. They showed the influence of communication competencies in how individuals manage conflicts. Their longitudinal model suggested some personal and relational factors, such as self-efficacy and relationship satisfaction. They found that individuals with higher communicative competence tended to manage conflicts more effectively, leading to better relational outcomes.

Authors like Wiemann [3] proposed other key variables that contribute to communicative competence. Among these variables, we can find the ability to understand and use language effectively (linguistic competence), sociolinguistic competence (the ability to use language appropriately in different social situations), strategic competence (the ability to manage communication breakdowns), psychological factors like emotional self-regulation, and interpersonal skills to interact with others effectively.

Regarding the stability of interpersonal skills and the influence of the context, Spitzberg’s perspective on interpersonal competence involves considering it a trait of personality, so a stable characteristic of individuals. However, this author also acknowledges that situational and contextual factors can influence the expression of these traits, so its manifestation can vary depending on the state or context [4].

Despite all these authors differing in the specific variables emphasized, they share core concepts on interpersonal competence, such as the need for adaptability in communication, emotional and cognitive regulation, and the importance of self-efficacy in social interactions. These theories also recognize competence as multidimensional.

Given the undoubted importance of the early development of interpersonal competence for several areas of life (personal relationships, emotional well-being, social and cultural adaptation, professional success), the interest in evaluating continuous and late development in more advanced stages of life, such as adulthood, makes sense.

The creation and adaptation of evaluation tests that measure this multidimensional construct are justified by their applicability in different contexts such as educational and training programs, not only for psychological interventions (therapy and counseling) or public policies for well-being.

The development and refinement of interpersonal skills between the age of 18 to 40 include the transition to young adulthood, the consolidation of personal and professional identity, and the formation of meaningful relationships, which may imply changes in social roles, making interpersonal competence particularly relevant in this period of life [5,6] (pp. 281–305).

Foschi & Hales [7] (pp. 244–254) emphasized the importance of identifying and understanding distinctive traits across diverse cultures, as they help define culture operationally by showcasing these characteristics in varying degrees.

There are societies that are either homogeneous or heterogeneous. Homogeneous societies, like Japan, are composed of individuals sharing similar racial, cultural, and historical backgrounds, while heterogeneous societies, like the U.S.A., consist of people with diverse backgrounds in these aspects. In homogeneous societies, the need to constantly define concepts or ideological debates is eliminated, and communication resembles that among family members, characterized by ambiguity in language and a reliance on non-verbal cues. By contrast, in heterogeneous societies, clear definitions and explanations are crucial in communication among individuals [8,9]. The differences between Western and Eastern cultures in these interpersonal competencies can be significant, hence the need to adapt psychological instruments that measure these variables for the corresponding culture. For example, they have created specific scales to assess interpersonal communication competence in Japanese culture that captures the essence of the indigenous competence of this population, like the Japanese Interpersonal Competence Scale (JICS) [10]. But when the objective is to evaluate common characteristics that may be essential in any culture to prevent certain problematic behaviors such as suicide, comparative studies need to be carried out using analogous tests in different countries so that traits occurring the most frequently or to a lesser degree can be equally weighted, allowing for more global comparisons. Rather than directly using the Western model to assess interpersonal competencies in Eastern countries, the key point would be to assess those transversal competencies that are common to different cultures with an important impact on problematic behaviors, regardless of cultural differences.

In 1988, Buhrmester, Furman, Wittenberg, and Reis developed the Interpersonal Competence Questionnaire (ICQ) [11], a 40-item self-administered instrument to assess five essential aspects of interpersonal competence: (1) starting interactions with others; (2) negative assertion; (3) emotional support; (4) self-disclosure; and (5) conflict management, of which an abbreviated version was later proposed (ICQ-15) by Coroiu et al. [12]. This brief instrument has been used with adults, but also in clinical populations [13] and adolescents [14,15]. The ICQ showed satisfactory psychometric properties in both its original proposal [11] and in its adaptations to other languages and/or cultures [16,17,18], as well as in its abbreviated 15-item form [12,14,15]. The consistency of the ICQ in results over time and across different contexts and populations ensures that this questionnaire effectively measures interpersonal competence, demonstrating its flexibility and applicability in different research settings.

Focusing specifically on these dimensions in Japanese culture, regarding the “initiation of interactions”, greetings and introductions seem crucial, something that can be seen reflected in the great variety of expressions or words that they can use in these contexts and also depending on the person they are addressing. Contrary to the advantages they may have over this first dimension, people in Japanese culture tend to avoid direct confrontation (“conflict management”) and open “negative assertions”, which can be reflected in their ambiguity when speaking (indirect communication) and implicit communication that is abstracted from the non-verbal. This implicit characteristic is also observed in the dimension of “emotional support”, where it can be expressed through actions rather than words. As for “self-disclosure”, the longer time necessary for the Japanese to build trust in others compared to those from Western cultures must be taken into account, in addition to the thought of inadequacy that can be perceived when expressing intimate issues, even feeling that the other is being burdened with problems for which only one is responsible [19,20].

Through the ICQ, the nature of various domains of interpersonal competence is explained, and their roles in social functioning are clarified [11]. Adapting a test like this, already validated in other languages and countries, allows us to use the same measures in cross-cultural studies focusing on measuring the same variables, so that they are representative of what is considered to be interpersonal competence. Also, using the short version of the ICQ, instead of its long version, has several advantages for the participants with whom it is administered, reducing perceived burden and fatigue, but also for its administrators, focusing on the most relevant items and being more concise to evaluate in those aspects. The brevity and ease of administration of its brief form (ICQ-15) can provide context for our approach and explain our motivation for its Japanese translation and cross-cultural validation with young adults. As a bonus, the abundance of resources and guidance on how to use and interpret the ICQ can reduce the time and effort required to implement the questionnaire in future studies. Also, it may be more accessible in terms of cost and availability.

Since this adaptation was carried out in a cultural context different from the original, focused on understanding Japanese culture, an emic perspective was adopted, which allowed the capture of culturally specific dimensions of interpersonal competence. Consequently, the objective of the present study was twofold:

(1)

To translate the brief form of the ICQ from Buhrmester et al. [11], the ICQ-15 from Coroiu et al. [12], and to adapt it to Japanese.

(2)

To evaluate the psychometric properties of this Japanese adaptation of the ICQ-15 for its possible use as an instrument for assessing interpersonal competence in Japanese adults.

2. Materials and Methods

2.1. Participants

The final sample consisted of 428 Japanese participants, recruited through a combination of convenience and snowball sampling. Although sampling was non-probabilistic, efforts were made to include a diverse population by contacting various Japanese institutions, beyond the educational sector, to help disseminate the survey. Participants completed the questionnaire online without a time limit.

The sample included 231 females (54.0%), 193 males (45.1%), and 4 participants self-categorized as non-binary (0.9%), with ages ranging between 18 and 40 years (11.7% 18–20 years, 54.9% 21–30 years, and 33.4% 31–40 years). Regarding education level, most participants were university graduates (56.54%), followed by high school graduates (28.03%). Regarding occupation status, the sample comprised mainly workers (n = 183, 42.75%) and full-time students (n = 169, 39.48%), followed by freelancers (n = 32, 7.47%), civil servants (n = 9, 2.10%), people working and studying at the same time (n = 6, 1.40%), unemployed individuals (n = 5, 1.16%), housekeepers (n = 2, 0.46%), and others (n = 22, 5.14%).

2.2. Measures

2.2.1. Sociodemographic Data

The participants were asked to report personal factors, such as gender (male, female, or other), age (3 ranges: 18–20; 21–30, and 31–40 years old), academic level (primary school; high school graduate; junior college graduate; bachelor’s degree; master’s degree; doctoral degree; or other), and occupation.

2.2.2. Brief Form of the Interpersonal Competence Questionnaire (ICQ-15)

The Interpersonal Competence Questionnaire [11] is a 40-item questionnaire that assesses interpersonal competence in five sections: (1) initiating relationships and/or conversations; (2) negative assertion; (3) emotional support; (4) self-disclosure; and (5) conflict management. Items are scored on a 5-point Likert-type scale, ranging from 1 (I feel uncomfortable and unable to handle this situation) to 5 (I feel very comfortable and could handle this situation very well). An abbreviated version of this questionnaire was later created, ICQ-15. The ICQ-15 [12] is a 15-item measure of interpersonal competence with the 5 subscales mentioned: (1) the initiation of a relationship subscale, which includes items such as “Introducing yourself to someone you might like to get to know/date”; (2) the negative assertion subscale, including items such as “Confronting your close companion when he/she has broken a promise”; (3) the emotional support assertion subscale, which includes items such as “When a close companion needs help and support, being able to give advice in ways that are well received”; (4) the disclosure subscale, including items such as “Letting a new companion get to know the “real” you”; and finally, (5) the conflict management subscale, which includes items such as “Not exploding at a close companion (even when it’s justified) in order to avoid a damaging conflict”. The items are rated on a 5-point Likert-type scale from 1 to 5, with higher scores indicating better interpersonal competence. The reliability of the original version was high; Cronbach’s alpha = 0.83 [12].

2.2.3. Communication Skills Questionnaire (CSQ)

The Communication Skills Questionnaire [21] is a self-report instrument designed to assess both verbal and non-verbal communication skills across a broad range of social contexts. It consists of 29 items divided into two parts: six items evaluating general communication skills—primarily non-verbal behaviors—rated on a 5-point Likert scale, and 23 items assessing interpersonal communication across six relationship types (e.g., with family, friends, and superiors), rated on a 3-point scale. The total score ranges from 0 to 306, with higher scores indicating greater communicative competence. The CSQ has demonstrated strong internal consistency (0.91 and 0.97), good test–retest reliability (0.90 and 0.95), and satisfactory convergent and discriminant validity, and has proven useful both in clinical populations and the general public.

2.2.4. Patient Health Questionnaire-9 (PHQ-9)

The Patient Health Questionnaire-9 [22] is a widely used self-report measure designed to assess the presence and severity of depressive symptoms based on DSM diagnostic criteria. It consists of nine items, each rated on a 4-point Likert scale ranging from 0 (not at all) to 3 (nearly every day), resulting in total scores ranging from 0 to 27. Higher scores indicate greater depressive symptom severity. The Japanese version of the PHQ-9 [23] has demonstrated good psychometric properties in previous studies, including high internal consistency and validity in both clinical and non-clinical populations, showing kappa coefficients of 0.79 and 0.97 for analog tests like the Mini International Neuropsychiatric Interview-Plus, with sensitivity between 0.84 and 1.0 and specificity between 0.95 and 0.99. It is commonly used in Japan as a brief screening tool for depression in research and practice settings.

2.3. Procedure

Regarding procedures, before creating the provisional Japanese version, we first obtained permission from the developers of the original ICQ and its brief form to translate it into Japanese by contacting some of the authors (Furman, W.; Körner, A.; and Brähler, E.). Then, two bilingual researchers fluent in both Japanese and English, co-authors of this study, Y.K. and K.A., were mainly responsible for the translation of the questionnaire.

K.A. was responsible for direct translation, translating each questionnaire item into Japanese. Backward translation was performed by Y.K. Subsequently, these two authors compared their translations until reaching a consensus. The back-translated version was examined and compared to the original English version to determine whether both versions were semantically equivalent to create a provisional Japanese version. The rest of the authors also reviewed it to address any discrepancies and reach a consensus on the final wording of the questionnaire. This involved comparing the translated version with the original questionnaire to ensure accuracy and consistency, which was then transmitted to the Japanese translation. No major problem was found.

Initially, a preliminary Japanese version was obtained, creating a coherent and faithfully translated version of the original content. This translation was pilot-tested with five native Japanese university students (n = 5). The phrasing of items 9, 10, 12, and 14 was revised for clarity (i.e., “in ways that are well received” in Item 9; “sensitive side” in 10; “productive outer shell” in 12; and “really” in 14). Along with this pilot test, cognitive interviews were conducted in this sample with the aim of analyzing both the level of understanding of the items and the response scale. We decided to use a Likert-type scale with 5 response options despite running the risk of choosing a neutral point to be faithful to the original version by Coroiu et al. [12]. Finally, the final version of the scale was applied to the experimental sample online and anonymously (n = 209).

The ICQ-15 scale was adapted for use in the Japanese language following the International Test Commission’s Guidelines for Test Translation and Adaptation [24]. Specifically, the original English ICQ items were translated using a forward–backward design to detect potential problems associated with poor translations [25,26]. Both the participants in the pilot study and those in the experimental study remained anonymous, and no incentive was provided to them. All subjects gave informed consent for inclusion before participating in the study by checking a box accepting this consent at the beginning of the online survey and could decide to withdraw from it at any time. The study was carried out in accordance with the Declaration of Helsinki and the protocol was approved by the Research Ethics Committee of the University of Murcia -(Nº: 4080/2022).

2.4. Data Acquisition

All the data reported in the present manuscript was gathered specifically for this study. Data acquisition was performed via an online survey, given the difficulty of accessing the Japanese population from the countries of the main authors (Spain and U.K.). All participants provided sociodemographic data and then completed the created ICQ-15 Japanese version outlined above.

Data from the pilot study was collected during December 2022 through an anonymous online survey under the direct supervision of K.A., in which a cognitive interview was also answered. In Supplementary Material S1, the first version of the questionnaire and the cognitive interview can be found. Based on the responses of these participants, revisions were made as necessary with clarifications until the final version of the questionnaire. Data from the first sample (n = 209) was collected from January to June 2023, and from the second sample (n = 219), from May 2024 until February 2025, where additional instruments (PHQ-9 and CSQ) were administered for convergent and divergent validity analysis, as well as through an anonymous online survey. We provide the final Japanese version of the ICQ-15 in the Supplementary Material S2.

2.5. Data Analyses

We began by conducting a descriptive analysis to determine each item’s mean score, standard deviation, and corrected item-total correlations. The items were not distributed following the normal distribution; therefore, analyses for ordinal variables, including polychoric correlation, were conducted. Confirmatory factor analysis (CFA) was performed with the Diagonally Weighted Least Squares (DWLS) method to examine whether the factor structure of the ICQ-15 version was consistent with that of the original instrument. Spearman correlations were used to assess the instrument’s convergent and divergent validity. Goodness of fit was assessed by means of the comparative fit index (CFI), the Tucker–Lewis index (TLI), the root mean square error of approximation (RMSEA), and the Standardized Root Mean Square Residual (SRMR). In the case of the CFI and TLI, values above 0.90 and 0.95 indicate acceptable and excellent fit, respectively. For the RMSEA and the SRMR, values below 0.08 indicate acceptable fit, and those below 0.06 indicate good fit [27]. Internal consistency was assessed by calculating ordinal omega coefficients for each dimension. Statistics were calculated using R 4.2.3, with the lavaan [28] and psych [29] packages. There was no missing data because all items needed to be completed before submission.

3. Results

3.1. Item Analysis and Internal Structure

3.1.1. Construct Validity

The items did not follow a normal distribution; that is, they did not cluster around a central value with a symmetric spread, so we needed to analyze them for ordinal variables, including polychoric correlation.

Table 1. Means, standard deviations, item-total correlations, and loadings for each item of the Japanese adaptation of the ICQ-15.

ICQ-15	M	SD	Skew	Kurt.	Corrected R	Stand. Loadings
Initiation of a relationship (α = 0.78; ω = 0.82)
ITEM 2	3.40	1.23	−0.44	−0.79	0.62	0.791
ITEM 7	2.89	1.28	0.05	−1.09	0.64	0.757
ITEM 9	2.92	1.27	−0.02	−1.09	0.59	0.781
Negative assertion (α = 0.84; ω = 0.88)
ITEM 10	3.07	1.27	−0.05	−1.07	0.63	0.762
ITEM 12	2.97	1.32	−0.05	−1.21	0.78	0.888
ITEM 13	2.99	1.27	−0.06	−1.11	0.72	0.888
Support assertion (α = 0.83; ω = 0.88)
ITEM 4	3.84	1.10	−0.80	−0.07	0.61	0.775
ITEM 11	4.17	0.96	−1.27	1.43	0.76	0.922
ITEM 14	3.95	1.02	−0.90	0.31	0.69	0.841
Disclosure (α = 0.76; ω = 0.81)
ITEM 3	3.09	1.32	−0.05	−1.19	0.54	0.775
ITEM 5	2.89	1.32	0.11	−1.14	0.68	0.767
ITEM 8	3.35	1.22	−0.30	−0.89	0.55	0.766
Conflict Management (α = 0.66; ω = 0.71)
ITEM 1	3.73	1.07	−0.77	0.03	0.50	0.765
ITEM 6	3.51	1.07	−0.53	−0.35	0.53	0.792
ITEM 15	3.61	1.19	−0.60	−0.59	0.40	0.389

Note: skew = skewness; kurt. = kurtosis; corrected r = corrected item-total correlation; stand. loadings = standardized loadings.

shows the means, standard deviations, homogeneity indices, and factor loadings for each item and the ordinal omega coefficient for each dimension. The means varied depending on the items’ dimension, and the highest values corresponded to the emotional support dimension. The homogeneity index (corrected item-total correlation) was above 0.35 for all the items, suggesting good internal consistency between the items, indicating that all items measured a common characteristic consistently. In addition, as can be seen in Table S1 and Supplementary Material S3, inter-item correlations were as expected, as correlations were, in general, higher between items in the same dimension than between items from other dimensions, except in the conflict management subscale, where a low or negative relationship between item 15 and the other two items in the factor can be found.

3.1.2. Confirmatory Factor Analysis

With respect to the factor structure, we can conclude that the model fit was acceptable [χ2 (80) = 197.34; CFI = 0.991; TLI = 0.988; RMSEA = 0.059, IC 90% [0.048, 0.069]; SRMR = 0.056], and standardized factor loadings of each item in its corresponding factor were above 0.40, except for item 15 (see Table 1), indicating that each item contributed significantly to the factor to which it belongs in the model, suggesting a strong and reliable factor structure. The values of the CFI (Comparative Fit Index) close to 1 and the TLI (Tucker–Lewis Index) are indicators of how well the model fits compared to a null model (a model with no relationship between its variables). The value of RMSEA (Root Mean Square Error of Approximation) also indicates an acceptable fit in terms of approximation error. The SRMR = 0.069 (Standardized Root Mean Square Residual) is another measure of model fit that evaluates the difference between the observed correlations and the correlations predicted by the model. This value indicates good model fit.

3.1.3. Internal Consistency Reliability

Regarding the correlations among subscales, all correlations were statistically significant, ranging in magnitude from 0.30 to 0.66 (see

Table 2. Latent correlation between the Japanese adaptation of the ICQ-15 subscales.

	F2	F3	F4	F5
F1. Relationship Building	0.47 ***	0.47 ***	0.56 ***	0.35 **
F2. Communicate negatives		0.42 **	0.47 ***	0.31 **
F3. Emotional Support			0.54 ***	0.66 ***
F4. Disclosure				0.52 ***
F5. Dealing with conflict

*** p < 0.001; ** p < 0.01.

). Finally, internal consistency indices were moderate to high (see Table 1), which is considered acceptable, indicating adequate reliability in the measurements. This suggests that the items within each subscale consistently measured the same construct.

3.2. Differences Among Groups

No statistically significant differences were found in the ICQ subscales in relation to gender (only people who self-identified as men or women were used in this analysis, since the sample of people self-identified as non-binary was too small). This suggests that gender did not have a significant impact on these aspects of interpersonal competence.

Age could be another indicator of the amount of social experience people acquire, so we would expect that those within an older age range would achieve better scores on the questionnaire. But, contrary to what was expected, no significant scores were found in any of the age ranges.

Regarding the variable “occupation”, the two large groups into which the sample was divided were the worker and student categories, which were quite balanced, but taking into account that there were many other categories in which the percentage of the sample was not representative, this result may not be significant.

Likewise, academic level could also be an indicator of better interpersonal skills, given the differentiation in treatment that is exhibited in Japanese culture due to the importance of hierarchy. In relation to this variable, the results were statistically significant with the dimension “emotional support”, but the effect size was small, and in the post hoc analysis performed to find which groups the difference was between, values close to significance were not found in any of them.

3.3. Convergent and Divergent Validity

To assess convergent and divergent validity, Spearman correlations were computed between the five ICQ-15 subscales, the PHQ-9—used as a measure of depressive symptomatology for evaluating divergent validity—and the CSQ—used to assess convergent validity. The results are presented in

Table 3. Spearman correlations between the Japanese adaptation of the ICQ-15 subscales, PHQ-9 and CSQ.

	PHQ-9	CSQ
F1. Relationship Building	−0.23 ***	0.34 ***
F2. Communicate negatives	−0.11	0.15 *
F3. Emotional Support	−0.08	0.24 ***
F4. Disclosure	−0.15 *	0.16 *
F5. Dealing with conflict	−0.09	0.13 *

*** p < 0.001; * p < 0.05.

.

As expected, all ICQ-15 subscales showed positive and statistically significant correlations with the CSQ, supporting the convergent validity of the instrument. The strongest association was found for relationship building (ρ = 0.34, p < 0.001), followed by emotional support (ρ = 0.24, p < 0.001), and disclosure (ρ = 0.16, p < 0.05). In line with expectations for divergent validity, low correlations were observed between the ICQ-15 subscales and the PHQ-9, indicating that interpersonal competence, as measured by the ICQ-15, is relatively independent from depressive symptoms. The highest correlation was observed for relationship building (ρ = –0.23, p < 0.001), while the rest of the subscales showed small or non-significant associations.

These results support the construct validity of the Japanese version of the ICQ-15.

4. Discussion

The aim of this study was to develop the Japanese adaptation of the brief form of the ICQ (ICQ-15) [12] and to evaluate its psychometric properties to achieve a specific tool used to measure and improve interpersonal competence in Japanese adults. Counting on the analysis carried out, it was successfully translated, and no issues with acceptability, comprehensibility, or relevance were identified. Overall, our results support the good psychometric properties of the Japanese version of the ICQ-15.

As a notable aspect, compared to other adaptations of the questionnaire in Western countries such as Germany, Japanese people may give lower scores in the subscales “communicate negatives” and “disclosure” due to the tendency of collectivistic cultures to keep social harmony, avoiding confrontational strategies that include expressing opinions contrary to the interlocutor, which generate conflict or express negative ideas [30]. The study of Luong et al. [31] examined these cultural differences, showing how the coping strategies used to manage interpersonal tensions affect emotional well-being. The more indirect and passive coping strategies of Japanese culture, although maintaining calm in the short term by avoiding confrontation, can negatively affect well-being in the long term because of unresolved tensions.

Furthermore, in Japanese society, communication is usually structured based on characteristics that place the person in a certain hierarchical position [32]. This aspect may especially affect the processes of “relationship building” and “emotional support”, factors also included in the ICQ-15. Although emotional expression in Japan can be more restrained to the inner circle compared to that in Western cultures and is usually better shown through actions rather than words [33], it remains a good indicator of interpersonal competence.

In this sense, the emic approach used for the adaptation of the ICQ-15 to Japanese, focusing on identifying and respecting the cultural specificities of the Japanese context, becomes especially relevant in the study of interpersonal competence. The Japanese Interpersonal Competence Scale (JICS), used for convergent validation, constructed from Japanese cultural values such as harmony, modesty, and hierarchical awareness, ensured that the adaptation of the ICQ-15 was not only linguistically accurate but also culturally congruent.

4.1. Comparison with Previous Studies

Regarding the construct validity of this Japanese version of the ICQ-15, the factor structure found in our confirmatory analysis coincided with the theoretical structure of the original questionnaire of Buhrmester et al. [11], as evidence that the measured construct can be universal. This test of solid factorial structure supports its validity as a psychological instrument of interpersonal competence in the Japanese population. Although the conflict management subscale showed less internal consistency, several versions have reported similar results to the lowest of the five subscales, considering it less conceptually cohesive [12,14,15].

The results of the factorial analysis of the Japanese version of the ICQ-15 showed a structure formed by five dimensions, keeping the expected multidimensionality of the tool assessing different interpersonal competencies. Comparing the data from the original model [11] with this Japanese version, both Bentler–Bonett fit indexes (CFI or NFI) are high, close to 1, suggesting good fits to their respective data. Although chi-square (χ2) values are not comparable between them because of their different sample sizes and degrees of freedom, the chi-square value is much higher in the Japanese version, which might be acceptable when adjusted for sample size and other factors.

With regard to reliability (internal consistency), the ω values were acceptable in all the subscales of the Japanese adaptation of the ICQ-1, very close to those obtained in the original version by Buhrmester et al. [11] (α values satisfyingly ranged from 0.77 to 0.87), but the first was measured with the omega coefficient (ω) and the second with Cronbach’s alpha (α), respectively, so the comparison should be carried out with caution and taking into account some key considerations, because it is important to consider other factors that could influence the results. But given that these values are higher in the adapted version when measured with the omega coefficient, it could indicate an improvement in the precision of the measurement to the new context (linguistic or cultural). Similar acceptable values were also found in the brief version (ICQ-15) by Coroiu et al. [12] and in other adaptations made for different languages and cultures [14,15,16]. This implies that the Japanese version of the questionnaire possesses psychometric characteristics comparable to those observed in other versions.

Consistent with previous research, certain sociodemographic and cultural factors may influence differences in interpersonal competence beyond gender, such as indirect communication and the tendency to maintain harmony between people. The values of harmony, respect, and discretion in social interactions influence how personal relationships and conflicts are managed, emphasizing the importance of courtesy and mutual consideration. These cultural dimensions could partly explain the scores observed on the interpersonal competence scales [20].

The results concerning convergent and divergent validity provide additional support for the construct validity of the Japanese version of the ICQ-15. The positive correlations observed with the CSQ align with theoretical expectations, suggesting that the ICQ-15 adequately captures dimensions of interpersonal competence that are meaningfully related to broader communication skills. At the same time, the relatively low associations with depressive symptoms, as measured by the PHQ-9, support the instrument’s discriminant capacity. While some overlap between interpersonal difficulties and depressive symptomatology is to be expected, the weak correlations reinforce the notion that the ICQ-15 assesses a distinct construct. These findings are encouraging, particularly given the limited availability of brief, psychometrically sound tools for assessing interpersonal competence in Japanese adult populations.

While the primary intention was to use the PHQ-9 for assessing divergent validity, given its focus on depressive symptoms, it can also be interpreted as an external criterion related to general psychological well-being. As expected, lower PHQ-9 scores were found in individuals with higher scores on the ICQ-15, supporting the scale’s criterion validity in the broader context of mental health, as research has indicated this relationship to be mediated by psychological factors such as need satisfaction, anxiety, and stress (Çıkrıkçı, 2024).

In line with the results reported by other similar interpersonal competence measures like the MSCS by Trevisan et al. [34], our study supports the usability of the Japanese version of the ICQ-15 in adults. Adapting a questionnaire like this, testing its abbreviated version mainly among adolescents, and using it with adults in another culture can pose some significant challenges. That is why it was important to make a good cultural adaptation that included, in its first phase, cognitive interviews to assess the understanding and relevance of the adapted items. In general, as far as it has been possible to test, our Japanese version of the ICQ-15, through forward–backward translation, has demonstrated validity, usability, and reliability to assess interpersonal competence in the Japanese-speaking population.

This study shows some strengths. The context of where the participants were recruited (most of them were college students) increased their likelihood of being familiar with the terms used in the questionnaire, avoiding misunderstandings about the content measured by it, since no complementary material was included that could have helped in case of not understanding any term during this phase. Though it may seem like a limitation due to the lack of generalization to other age groups, a specific age range (adults from 18 to 40 years old) can offer, regardless of sample size, several advantages, allowing a more coherent and precise analysis by minimizing variability because of age differences and facilitating a more detailed and in-depth study of their responses. By selecting a relatively homogeneous population in terms of life stage and environment, even though it can be a limitation, we can better isolate the specific factors we are investigating by controlling variables that could confound the results. Some studies have shown that young adults in the college environment develop crucial competencies for adult life, such as autonomy, self-regulation, and problem-solving skills [35].

4.2. Limitations

There are several potential limitations to this report, beginning with the number of people involved in the cognitive debriefing process (pilot test with n = 5) conducted to verify that all items were appropriate and understood by the participants. Although the final sample increased to n = 428, this remains modest compared to the samples of other ICQ-15 validations [14,15]. Moreover, the sample was recruited from non-clinical settings, which may introduce a degree of homogeneity that limits the generalizability of the findings.

While the sample was not specifically drawn from a clinical population, this limitation is less critical given the main objective of the study was to adapt and validate the ICQ-15 for use in the general Japanese adult population, rather than for clinical diagnostics. Although the absence of a clearly defined clinical group could be seen as a limitation, it is important to note that participants were not screened for clinical status, and it is therefore possible that some respondents were, in fact, part of a clinical population. A potentially more significant limitation concerns the non-random nature of the sampling procedure. However, efforts were made to maximize the diversity and heterogeneity of the sample by disseminating the survey widely across different types of institutions and networks, aiming to reach a broad cross-section of Japanese adults.

Although the JICS was used for valid cultural criteria, it is difficult to integrate cultural elements specific to the Japanese context without falling into essentialism, since the emic approach tends to reproduce a homogeneous view of, in this case, Japanese culture, and can contribute to reinforcing cultural stereotypes. Without strictly adhering to the same standards as the JICS, this adaptation of the ICQ-15 attempted to align with this vision, not as a fixed truth, but as a useful heuristic tool for theoretical and practical development. Regarding reliability, some aspects were not evaluated. A test–retest was not performed. Therefore, we cannot know if these scores would vary over time. Lastly, the interrater reliability was not measured, but it was not a particularly relevant measure here either, since it is not a subjective-measure questionnaire.

4.3. Future Lines of Research

To identify the communication characteristics of the participants, more reliability and validity assessments of the Japanese version of the ICQ-15 are needed for use in various settings. Future research should consider including more diverse and clinically representative samples to further validate the instrument. Additionally, we would like to examine criterion-related validity, including more diverse indicators such as self-esteem or life satisfaction, to further explore the external validity and temporal stability of the scale.

5. Conclusions

Given the versatility of the ICQ-15 to measure the variable of interest in this study, interpersonal competence, in different languages and cultures, we successfully developed a Japanese version of this assessment tool. Overall, the ICQ-15 showed good reliability and validity in the Japanese adult population, resulting in an instrument that requires less time and resources compared to other similar instruments to measure interpersonal skills, such as the JICS [10] or the CSQ [21].

Considering that the intent to use this questionnaire in future studies that involve the comparison of said variables with other cultures (cross-cultural research), making this adaptation ensures that the items are culturally relevant and reflect behaviors and social norms typical of Japanese culture.

Of course, we must highlight its practical implications beyond the research, since academic (universities or higher education due to the age range tested) and clinical environments can use the adapted questionnaire to evaluate and develop interpersonal skills effectively. This can be crucial for training programs, professional development, and therapeutic interventions. It is hoped that the development of the Japanese version of the ICQ-15 will promote its use in Japan.