Could you be a little more specific?

“The Matses are a 2,500-strong tribe, and they live in the tropical rainforest along the Javari river, a tributary of the Amazon. Their language, which was recently described by the linguist David Fleck, compels them to make distinctions of mind-blowing subtlety whenever they report events. To start with, there are three degrees of pastness in Matsese: you cannot just say that someone ‘passed by there’; you have to specify with different verbal endings whether this action took place in the recent past (roughly up to a month), distant past (roughly from a month to fifty years), or remote past (more than fifty years ago).  In addition the verb has a system of distinctions that linguists call ‘evidentiality’, and as it happens, the Matses system of evidentiality is the most elaborate that has ever been reported for any language. Whenever Matses people use a verb, they are obliged to specify – like the finickiest of lawyers – exactly how they came to know about the facts they are reporting. The Matses, in other words, have to be master epistemologists. There are separate verbal forms depending on whether you are reporting direct experience (you saw someone passing by with your own eyes), something inferred from evidence (you saw footprints on the sand), conjecture (people always pass by at that time of day), or hearsay (your neighbour told you he had seen someone passing by). If a statement is reported with the incorrect evidentiality form, it is considered a lie. So if, for instance, you ask a Matses man how many wives he has, unless he can actually see his wives at that very moment, he would answer in the past tense and would say something like daëd ikoşh: ‘two there-were [directly experienced recently]’. In effect, what he would be saying is ‘There were two last time I checked’. After all, given that the wives are not present, he cannot be absolutely certain that one of them hasn’t died or run off with another man since he last saw them, even if this was only five minutes ago. So he cannot report it as a certain fact in the present tense.

“But finding the right verbal form for directly experienced events is child’s play compared with the hair-splitting precision required when you report an event that has only been inferred. Here Matses obliges you to specify not just how long ago you assume the event occurred but also how long ago you made the inference.”

And if you think that’s bizarre, wait until you hear about the Guugu Yimithirr people’s use of geographic directions.

Guy Deutscher, Through the Language Glass