The Croatian capital, Zagreb, has historically been a Kajkavian-speaking area, and Kajkavian is still in use by its older and (to a lesser extent) by its younger population. Modern Zagreb speech has come under considerable influence from Shtokavian. The vast intermingling of Kajkavian and standard Shtokavian in Zagreb and its surroundings has led to problems in defining the underlying structure of those speech-groups. As a result, many of the urban speeches (but not rural ones) have been labelled either "Kajkavian koine" or "Kajkavian–Shtokavian" rather than Kajkavian or Shtokavian. Additionally, the forms of speech in use exhibit significant sociolinguistic variation. Research suggests that younger Zagreb-born speakers of the Kajkavian koine tend to consciously use more Kajkavian features when speaking to older people, showing that such features are still in their linguistic inventory even if not used at all times. However, the Kajkavian koine is distinct from Kajkavian as spoken in non-urban areas, and the mixing of Shtokavian and Kajkavian outside of urban settings is much rarer and less developed. The Kajkavian koine has also been named "Zagreb Shtokavian" by some.