A Slovak tourist on a holiday in Croatia who wants to communicate with the locals has several options at hand (Backus, Marácz, and ten Thije 2011). She can use English and hope that the English of the locals as well as her own is at a level that is sufficient for mutual understanding. According to a report by the European Commission (Special Eurobarometer 243), however, only 38 % of EU citizens can speak English well enough to be able to hold a conversation, so the odds are that our tourist cannot really communicate that way. She could perhaps try German, which is commonly taught in schools in both Slovakia and Croatia, so it might perhaps qualify as some sort of a regional lingua franca. The odds of that working are even slimmer, since only 11 % of EU citizens report they are able to have a conversation in German (Special Eurobarometer 243). If she could speak a bit of Croatian, perhaps another option might be code-switching, i.e. speaking a bit of both languages, in the hope that she could create a mix that would enable mutual intelligibility. Since her Croatian is limited to the two or three most basic phrases, this option is also out.

What is our Slovak tourist to do then? She could attempt to simply speak her native language and let the locals speak Croatian, while she would try to understand as much of it as she can. Croatian speakers would do the same thing: speak Croatian and try to actively understand Slovak. This type of communication is called receptive multilingualism and our tourist is quite familiar with it: she talks to Czech speakers all the time in this manner (Nábělková 2007). The same mode of communication is also used in Scandinavia, between speakers of Swedish, Danish and Norwegian (Delsing and Lundin Åkesson 2005) as well as between some speakers of German and Dutch (Ribbert and ten Thije 2007), Finnish and Estonian (Verschik 2012) etc.

Could receptive multilingualism work between a speaker of Slovak and a speaker of Croatian? The success of their actual communication would depend on a number of factors, some of which might be the complexity of the topic, the speakers’ willingness to use this type of interaction, their previous experience with using receptive multilingualism, their cooperativeness, and the urgency of the situation. But the most important factor would certainly be the actual level of mutual intelligibility between the two languages. If a speaker of French and a speaker of Hebrew were to give receptive multilingualism a try, even with all the good will in the world, they would not get past the most basic interaction, probably one focusing on gestures. If the two languages in question belong to the same language family, as is the case with Slovak and Croatian, the odds are that some level of mutual intelligibility might be established.

In their 2007 report, the High Level Group on Multilingualism established by the European Commission called for research efforts into receptive multilingualism with regards to Germanic, Romance and Slavic language families. The Mutual intelligibility of closely related languages (MICReLa) project¹ was set up with the goal of measuring the level of mutual intelligibility within these three language families as well as to examine the linguistic and extra-linguistic factors influencing intelligibility. The level of intelligibility between two languages approximates how well a speaker of language A could understand a genetically related language B and vice versa. Related languages share a certain percentage of cognates, i.e. words with a common origin which more often than not have a similar form. Their phonological, orthographic, morphological and syntactic systems are likely to be much more similar than the systems of completely unrelated languages. All this could help our speaker of Slovak to understand Croatian. Finally, extra-linguistic factors might also play a role in intelligibility. A positive attitude to a related language could be related to the success in decoding it (Schüppert, Hilton and Gooskens 2015). The amount of contact with this language is also bound to play a role: the more exposed a listener is to a related language, the more likely she is to understand it. The end result of the project is to create a general model of mutual intelligibility taking all the aforementioned factors into account.

The aim of the present paper is to describe the first step towards this model: the empirical testing of the level of mutual intelligibility between six Slavic languages: Czech, Slovak, Polish, Croatian, Slovene and Bulgarian. In order to get as complete a picture as possible, we tested intelligibility using three different methods and all three methods were used with both written and spoken language. The idea is to establish the level of receptive mutual intelligibility—to measure, for instance, how much written or spoken Croatian can a person understand on the basis of their native language, as well as their knowledge of or exposure to other languages of the same family?

Our first research question is: what is the level of mutual intelligibility between Czech, Slovak, Polish, Croatian, Slovene and Bulgarian? Keeping in mind that in the present study we are dealing with languages belonging to two distinct branches of the Slavic language tree, we hypothesize that in most cases, the distinction between West Slavic (Czech, Slovak, Polish) and South Slavic languages (Croatian, Slovene, Bulgarian) will be kept, i.e. a speaker of Polish will always understand Czech and Slovak better than any South Slavic language. The only exception to this pattern could be Bulgarian, which is characterized by an almost complete loss of case in all declensions; the creation of definite articles from demonstrative pronouns and a complex tense system where the infinitive is now completely lost but the distinction into indicative and renarrative tenses emerged (Townsend and Janda 1996). A potential consequence of this discrepancy between Bulgarian and other Slavic languages might be that speakers of Croatian and Slovene could understand Czech and Slovak, West Slavic languages, better than Bulgarian.

We propose that the most intelligible language combination will be Czech-Slovak, not only because of their great linguistic similarity, but also because of a great amount of contact (Nábělková 2007). Polish belongs to a separate sub-family, Lechitic (Rothstein 1993), so the degree of intelligibility between Czech and Polish and Slovak and Polish should only be moderate. We do not expect a high degree of intelligibility across language sub-families, so the second most intelligible language combination should be Croatian-Slovene because Bulgarian is so dissimilar to both of them. In addition, Croatia and Slovenia share a border and have some transitional dialects as well as some degree of exposure to one another.

Our second research question is whether the level of mutual intelligibility is always symmetrical. The asymmetric intelligibility between Czech and Slovak, whereby speakers of Slovak understand Czech better than vice versa, has been a much debated topic after the breakup of Czechoslovakia (Nábělková 2007). Similarly, while Slovenia was a part of Yugoslavia, many native speakers of Slovene were bilingual in Serbo-Croatian as well and some anecdotal evidence seems to suggest that native speakers of Slovene can still understand Croatian better than vice versa. Therefore, we hypothesize that we will find asymmetric intelligibility levels in Croatian-Slovene and Czech-Slovak language combinations.

Our third research question concerns the reliability and suitability of the three methods we are using: the word translation task, the cloze test and the picture task. We shall examine whether they all give a similar pattern of results.

In Sect. 3, we present previous research into mutual intelligibility of closely related languages with a focus on methodology. In Sect. 4 we describe all three methods for measuring intelligibility used in the study. In Sect. 5 we present the results; Sect. 6 is reserved for a discussion of our results and special attention is paid to the three methods and Sect. 7 for a conclusion and future directions.

We shall begin by discussing the three methods used in the study and whether all three yield a similar pattern of results. The results obtained from the word-translation task and the cloze test are quite similar to each other: the participants were always more successful at translating words than they were at doing a cloze test in a closely related language, but the overall pattern is the same. The story is somewhat different for the written and the spoken picture task. Firstly, we observed some peculiar findings: Croatian participants were more successful at understanding Slovene than Czech participants were at understanding Slovak, which we had not predicted would be the case. The same finding was observed with Slovene participants undertaking the task in Croatian—they were equally or more successful in choosing the correct picture than Slovak participants reading / listening to Czech. Secondly, we had not expected Bulgarian to be less intelligible to Croatian than Polish is, but the results of the written picture task seem to indicate this is the case. Slovak participants were almost as good at Croatian in the spoken picture task as they were at Czech, and they had exactly the same score in Croatian than they did in Polish. Thirdly, the results from the written and spoken picture task did not correlate as highly as the results from the two word-translation tasks and the two cloze tests did. Considering that the chance of choosing the right answer was 25 % for this task and coupling it with unexpected findings and somewhat lower correlations with the results of the other two tasks, we were led to conclude that the picture task is not the best way of measuring global intelligibility, at least not in the way we conceived it. Therefore, in the remainder of the discussion, we shall focus on the results from the other two methods only.

Our first research question was explorative in nature and was concerned with the level of mutual intelligibility between three West Slavic languages (Czech, Slovak and Polish) and three South Slavic languages (Croatian, Slovene and Bulgarian). The hypothesis that the Czech-Slovak language combination would have the highest level of mutual intelligibility was confirmed both in the results of the word-translation task and the cloze test. As expected, the Croatian-Slovak language combination was the next to follow. Such a high level of mutual intelligibility between Czech and Slovak indicates that receptive multilingualism is definitely possible, and since we already know that this method of communicating is practically the norm between the speakers of those languages, we conclude that the near-ceiling effect we found is valid. With regards to Croatian and Slovene, our results indicate that receptive multilingualism is generally possible, however, Croatian speakers might have a particularly hard time understanding spoken Slovene. To our knowledge, there was no previous research into Croatian-Slovene mutual intelligibility to confirm this.

Overall, we found moderate levels of mutual intelligibility between the speakers of Polish on one hand and Czech and Slovak on the other. Some degree of receptive multilingualism could be possible with these language combinations as well and anecdotal evidence indicates that there is indeed such communication, particularly in border areas. Sussex and Cubberley also note that all West Slavs can communicate with one another “to some extent” (2006, p. 3).

Bulgarian proved to be the least intelligible language in our study. In both written and spoken cloze test, Croatian and Slovene speakers were as successful when dealing with Czech and Slovak as they were when dealing with Bulgarian. This result stands despite the bias that all the participants who did the written tasks in Bulgarian could read Cyrillic and therefore might have learned another Slavic language written in Cyrillic, such as Russian.

Bulgarian participants overall had the lowest intelligibility scores out of all six native language groups. A part of this finding for the written tasks might be explained by the fact that unlike other participants, native speakers of Bulgarian had to read words or texts in Latin, which is not the alphabet of their native language. But since the results persist in the tasks dealing with spoken language as well, we conclude that the linguistic distance might be the reason for such levels of (un)intelligibility. Our study did not include Macedonian or southern dialects of Serbian, which are also characterized by the loss of cases and consequently, more preposition-based syntax. This means that there is a great discrepancy between Bulgarian on one hand and the other five languages we looked at on the other. The next step of the present project is to investigate the role of linguistic and extra-linguistic factors in the mutual intelligibility of Slavic languages, which should give a definite answer to this question. In the meantime, we can safely conclude that all language combinations from our sample involving Bulgarian can only use receptive multilingualism to a very limited degree.

When it comes to mutual intelligibility across language sub-families, it seems that the speakers of Czech and Slovak can understand Croatian to some extent, particularly in the written mode. With spoken language, however, their abilities are substantially reduced. Since there are features in Croatian phonology, morphology and syntax that are difficult to grasp for a speaker of a West Slavic language, it might be the case that Czech and Slovak speakers might benefit from a teaching program targeted at those differences, perhaps something similar to EuroCom Slav, which is still being developed (Zybatow 2003).

Our second research question was aimed at potential asymmetries in intelligibility. Our hypothesis was that Slovak speakers would be better at understanding Czech and that Slovene speakers would be better at understanding Croatian than the other way around. This hypothesis was only partly confirmed, since we did not find a significant difference in intelligibility levels for Czech-Slovak and Slovak-Czech. While there was indeed a difference in score in favor of Slovak participants, both sets of scores were so high that the difference was not significant. The hypothesis to do with asymmetric intelligibility between Slovene and Croatian was confirmed, since we found statistically significant differences both in the written and in the spoken cloze test. Future research is needed to show whether that difference arises due to linguistic factors, extra-linguistic factors, or the complex interplay of both. Our working hypothesis favors this third option, since there are some transitional dialects between Croatian and Slovene, indicating both a degree of linguistic similarity and at least some language contact in the border area.

Since both the cloze test and the word-translation task resulted in a similar and plausible pattern of results, we conclude that both methods are suitable for measuring the mutual intelligibility of closely related languages within such a varied language family as Slavic. The picture task resulted in some illogical findings, which might indicate that the (mis)understanding of single words that were highly relevant (e.g. the word for bicycle in a text about riding a bike) might have played a larger role in the results than the actual ability to understand a related language.

The present study used three different methods of measuring mutual intelligibility: the word translation task, the cloze test and the picture task. The word translation task and the cloze test had the same pattern of results, while the picture task in its present form is probably not a good way of measuring intelligibility. We found that Czech and Slovak have by far the highest level of mutual intelligibility, followed by Croatian and Slovene. In the case of Croatian and Slovene, the intelligibility is asymmetric, since Slovene participants could understand Croatian better than vice versa. The division into West and South Slavic languages is well preserved in the results, except in the case of Bulgarian, which is not very intelligible to the speakers of other South Slavic languages. Given that we did not include Serbian or Macedonian, which share some features with Bulgarian that Croatian or Slovene do not, it might be the case that this discrepancy within the South Slavic language family is a consequence of our language choice, rather than an inherent feature of Bulgarian.

Now that the general levels of mutual intelligibility between Czech, Slovak, Polish, Croatian, Slovene and Bulgarian have been established, we call for more research into the mutual intelligibility of other Slavic languages. The addition of the East Slavic language family would enable another set of comparisons and the inclusion of smaller languages such as Macedonian or minority languages such as Upper and Lower Sorbian would lead to a more complete picture.

Another interesting line of research partly covered by the MICReLa project would be measuring the influence of linguistic and extra-linguistic factors on intelligibility. How much do the differences in lexicon, phonology, syntax etc. influence intelligibility and how much does language exposure, for instance, play a role? Such findings would help us to answer to the question of whether the asymmetry in our results for Croatian and Slovene is due to differences in language structure or simply due to asymmetric contact between the speakers of the two languages.

Since the idea of measuring global intelligibility using pictures shows some promise and we hope that future studies will arrive at a more successful way of applying the method. We propose a finer-grained task, perhaps with a sequence of pictures describing a story, where some of the details in the pictures contradict the story and the participants’ task is to select the correct sequence of pictures. The successful applications of a picture task would be of great use to the field, since it would enable the administration of the task to populations such as small children or illiterate participants or, as in our case, participants who are unable to read the script of one of the test languages.

Finally, there are other approaches to mutual intelligibility besides quantitative ones. Qualitative research into the mutual intelligibility of Slavic languages would reveal what strategies different Slavic speakers use to make themselves understood and how successful inter-Slavic communication really is in a more naturalistic setting. On a more applied note, receptive multilingualism could also be taught: if our Slovak tourist decides from the outset to spend a longer time in Croatia, she might not need to learn Croatian. She could instead focus on learning how to understand it and to speak Slovak so that native speakers of Croatian can understand her. Developing and testing such learning programs is another course research into this topic could take. Hopefully all these new insights will give us a more complete picture of intelligibility in the Slavic language area.