Even though there is more to schizophrenia than just hearing voices, it is certainly an integral part of the illness. However, studies have shown that the aspect surrounding voices could be more complex than we initially thought.
It is believed by some experts that the voices and what they are effectively saying to the individual can vary depending on the culture and country that you find yourself in or influenced by.
As an example, the study showed that there is a tendency in America for people that are schizophrenic to hear voices that are telling them to carry out violent acts more than anything else. At the same time, if you go to Africa, then they tend to hear the voices of their ancestors since that plays a huge part in their heritage and culture.
Alternatively, in India they often hear voices that are far more comforting and positive in nature over and above anything else. Quite why there is this sense of variation is not fully understood, but it is accepted that culture does play a huge part in shaping the voices in our head.