I'm looking for a book (or series of books) which I read as a kid (around 1995). I don't know a lot about the storyline anymore but I remember that there were two distinct alien races in the book with whom humans interacted. One of the races was lizard-like and had as a trait that they had sort of a bladder that filled up when they were upset. When it was full they would go to some sort of temple and release it. They then went completely berserk and fought each other. Sometimes, when they didn't make it to a temple in time, this could happen in the outside world. I think the other race focussed on bio-organic and space ship development and I think they were shaped like small pyramid, but I'm not entirely sure about the last part. Any help would be greatly appreciated.
Bit of a guess, but I recall a short SF story, written in Dutch, that matches it very well. (And your name sounds Dutch, so...)
The story was called "Misdaad en straf" ("Crime and punishment"), apparently as a reference to the famous literary work. Unfortunately, this makes it a pain to Google.
The short story involves two space travellers encountering one of these pyramid-shaped aliens. IIRC the alien was space-shipwrecked and they were required by law to take the alien aboard. To their horror, his "anger" bladder was almost full, meaning he could go amok (the literal word the story used) any time soon.
The two travellers decided to empty the sleeping aliens "bladder" - which these pyramidical aliens consider extremely rude and offensive. When the alien awoke, it realized what had happened. Deeply insulted, it deliberately worked itself into a state of anger to re-fill its "bladder" and make amok after all.
The story ends with the two human travellers being sentenced to live in a forest on the alien's home planet. The forest responds to emotion - answering violent anger with violent anger. For these aliens, who must regularly release their anger in a furious rage, this is effectively a death sentence. But since the two travellers are humans, they can keep their anger under control, and live on.