[mgraczyk]

When I worked at Instagram, no psychologist or neuroscientist was ever involved in any part of product development, experimentation, or parameter refinement in any way.

Sometimes "psychologists" (product analysts?) looked at data and wrote reports. This was generally used for very high level product direction, and had more to do with reading the pulse on what people want rather than any kind of actual "psychology".

For example, did you know that US teens don't like to see "too many" memes on their feed? These are the kinds of questions "psychologists" at facebook are answering. There simply does not exist any technology to use "psychology" to optimize low level parameters for engagement metrics.