Yes, there are some similarities. For instance, being a Bengali speaker and knowing Hindi, I do understand Assamese, Oriya and Marathi if they are spoken at a slow pace. If one knows Hindi, Gujarati can also be figured out to some extent. Same goes for Urdu. The South Indian languages are totally different, and within that group Malayalam (Adoor's films are in that language) has little or no resemblance to the other three. The fascinating thing is that in Pondicherry, which used to be a French colonial bastion, Tamilian rickshaw guys speak fluent French. Loads of spoken languages in different parts of the country are still not recognised as official languages. Language is such a political thing and there are such issues of power involved in marginalising some and elevating others! You should come here sometime, A