How to design chatbots with the right level of human-like characteristics

The 'uncanny valley' is a known phenomena when it comes to designing robots with human-like features and traits.

However, as a previous question suggested, there is not much work done in this area of design or research.

Given the variation of names, appearances and interactions seen in current chatbot designs for a variety of use cases, it seems likely that there is still a lot of trial and error in the design specifications and requirements in this area.

My question is: are there design guidelines around how to mimic (or not mimic) human behaviour when it comes to chatbots and digital avatars?