I am the father of a 9-month-old girl. I am divorced and my ex-wife speaks only Hebrew with the baby while my mother language is Russian. I am also able to speak Hebrew. I see the baby for about 15-20 minutes every two weeks. I would love her to speak Russian but is that realistic? Does it make sense to speak Russian with her or will it just confuse her?
This is one of those rare cases where there's been a scientific study on exactly this topic!
The short answer is yes, speaking Russian with your 9mo daughter --- even for just the short visits you describe --- likely will help her build a foundation for learning Russian in addition to the language(s) she is exposed to more regularly.
Kuhl, Tsao and Liu (2003) examined the effect of short-term exposure to a foreign language for infants right around 9 months of age.
All of the infants participating in the experiment were hearing only English at home (the study was done in Seattle, WA). For the study, they were randomly assigned to the foreign language exposure group or a control group. Infants came in to the lab (with their parents, of course) and spent 25 minutes reading books and playing with an experimenter who was either speaking Mandarin (the foreign language exposure group) or English (the control group). Infants came in for 12 of these sessions over a four week period, so a little more frequent than the visits you have with your daughter but still probably comparable.
At the end of the 12 sessions, they tested the infants on their ability to distinguish tricky speech sounds in Mandarin, something that infants learning just English aren't able to do well by 10 months or so. Infants who got short-term exposure to Mandarin performed about as well as infants in China learning Mandarin as their first language. This suggests that even very limited, short-term exposure to speakers of another language can result in meaningful learning of speech sounds for infants at 9 months.
Note that the researchers ran a second version of the study where they used videos or audio recordings for the foreign language exposure instead of an in-person interaction, and it didn't appear to have any effect on learning at all; at least at this age, interacting in person seems to be an important requirement for infants to learn about speech sounds.
Prof. Kuhl also discusses this study (and other relevant work) in her TED talk, where she shows recordings of the study sessions, so you can see better what I'm describing here.
What level of learning can be expected from this kind of language exposure?
Note that the study showed that infants at your daughter's age showed clear signs of maintaining sensitivity to the speech sounds of the foreign language they heard, but the researchers didn't test for any other aspects of language development or conduct any follow-up research on later effects of this kind of exposure. For example, this research doesn't tell us whether or not you should expect your daughter to start saying Russian words around the same time she starts speaking Hebrew --- my guess is she will be much slower to learn Russian than Hebrew.
But this research does clearly demonstrate that even limited exposure to another language at 9 months --- like the kind of exposure you're talking about with your 20 minute visits --- can help infants to maintain sensitivity to the speech sounds of that language. Even if she doesn't appear to be learning or using Russian words much over the next couple years, if you keep speaking Russian to her that will keep her brain open to the unique patterns of Russian sounds, and she'll have a serious advantage if she shows interest in learning it later. That may be the difference between her eventually being able to speak Russian like a native, with perfect pronunciation, versus sounding like she learned it in school.
This is about the amount of exposure to Russian that my son gets, and at age 3, he certainly does not speak Russian. However, he recognizes some frequently heard words and phrases and knows what they mean (questions, commands, the names of his toy animals...), and he sometimes repeats back to me the things I say, with closer and closer approximation of the right phonemes. This last part is key to my answer: yes, speak Russian with her, because it is likely that she will be interested in learning the language later in life, and exposure to the sound inventory of the language now will give her a huge advantage later on, no matter how small a lexicon she acquires at this stage. I would add the caveat though that you should also be willing to speak Hebrew with her - 20 minutes every now and then isn’t enough for the immersion she would need to have a usable second language, so until/unless you have her for longer periods in the future, you would be putting an insurmountable language barrier between the two of you if you insisted on only speaking Russian.
Sure, speak Russian with her.
will it just confuse her?
It will probably set back her language acquisition a bit if she's learning two languages instead of one, but that's normal. Bilingual toddlers start speaking a bit later than others and are often less proficient in both languages in the early years, but by the time they reach kindergarden, that should even out and they'll be speaking two languages instead of just one.
Is that realistic?
It probably won't do a whole lot with just 20 minutes every 2 weeks, but that might change in the future when you see her more often. I don't know if there are any studies about how much good 20 minutes of a second-language every 2 weeks will do - I'd assume that this is little enough so as to not make a dent in primary language acquisition, but it might also not be enough for her to actually learn Russian.
Still, if I were you, I'd try it. I can't imagine any lasting ill effects from this, and if it doesn't work, you can still switch to Hebrew later on.
You can talk to her in Russian, but repeat in Hebrew till she's able to understand. If she's seeing you only once in 2 weeks, chances are she'll forget those words by her next visit but over a period of time, she will understand regular/repeating phrases or words. Children can pick up many languages easily but to be able to speak fluently, they need time and people to speak to.
Since your daughter spends very limited time with you, she may not become fluent in Russian. However, even a couple of words learnt at this age would help her pick up the language faster sometime in the future (if needed) so do keep talking. As she grows older, you can suggest some language classes near her or an online class so that she can talk to anyone from her dad's family who doesn't speak hebrew.