What makes, or breaks, our ability to understand other languages related to our own

We are interested in the nature of comprehension and incomprehension between speakers of different, but related, languages (e.g. Spanish and Italian, or German and Dutch).

How do native speakers of one language go about making sense of, or creating meaning from, another language which is similar to their own?

Does the expectation that they won’t understand prevent them from understanding when otherwise they could? Is this expectation self-reinforcing?

What do speakers tell us about their expectations when faced with other languages?

What aspects of a language make it opaque or transparent to speakers of another as they seek to create meaning?

By what strategies do speakers create bridges for linguistic comprehension?