Are there any studies on the effectiveness of learning typologically similar languages?

Question

Flimzy previously asked, Are there any studies which address the effectiveness of studying multiple related languages simultaneously?

Genetic relationships between languages (as established through comparative linguistics) can lead to similarities that can lead to certain advantages when learning languages from the same family (e.g. multiple Germanic languages, multiple Slavic languages, etc.)

However, languages can also have similarities without being historically related. Linguistic typology is the field of linguistics that "studies and classifies languages according to their structural and functional features" (Wikipedia).

One important language feature concerns the basic order of subject, verb, and direct object in sentences, e.g. subject–verb–object (SVO) languages (English, Chinese, French, ...), verb–subject–object (VSO) languages (Arabic, Irish, Tagalog, ...), etc.

Other language features identified by linguistic typology concern morphosyntactic alignment, morphological features (analytic and synthetic languages) and the general order of time, manner and place.

Learning a (genetically unrelated) language with many typological similarities to one you know is presumably easier than learning a (genetically unrelated) language with fewer typological similarities. Even though this sounds plausible, I would like to know if any studies have been done on how these typological similarities facilitate language learning.

Answer 1

According to New Perspectives on Transfer in Second Language Learning (emphasis mine),

Relative typological distances between given L1s and an L2 are sometimes conceptualized as different starting points for those acquiring that L2, with learners who speak a more distant L1 viewed as facing a longer journey. Successful L2 language processing, including lexical inferencing and related lexical acquisition, is likely to be relatively facilitated for learners whose native language is typologically similar to the L2. This is because cross-linguistic similarities provide greater possibilities for positive transfer, freeing up cognitive resources for other language learning tasks. The result may be more rapid acquisition rates and, over time, cumulative advantages in subsequent comparative proficiency.

In addition, a scientific study that focused on adapting Japanese grammar to Korean, Porting Grammars between Typologically Similar Languages: Japanese to Korean concluded that

But more generally, we conclude from this limited experiment that porting grammars across typologically similar languages is an effective method for bootstrapping grammar development.

From this, it can be concluded that typologically similar languages share many common features in vocabulary and grammar, thus vastly facilitating the process of learning a typologically similar L2 for a language learner.