It seems that it is the breadth – not the depth – of experience abroad that is a significant factor for immoral conduct on the part of overseas travellers. So it is not so much a question of an extensive stay in one country, but rather of visiting many countries, even if for a shorter period of time.
Researchers from the INSEAD business school discovered the probable reason may be that well-travelled people have lived in several different cultural environments and developed a more flexible sense of what is right and wrong.
Their approach is then one of moral relativism and this may result in behaviour that we would describe as immoral.