A few thoughts on the difficulties of humanities scholars using scientific papers:
Accessibility: Especially with technical language and assumed knowledge. This discourages researchers from using valuable scientific studies. You are also probably less informed in trends of scientific research and what might be out there to read up on.
Understanding: Most UK humanities students do not also have an understanding of degree level science. Interestingly, this doesn’t necessarily apply to American students (and elsewhere) where an undergraduate course is more flexible and the arts and sciences aren’t barricaded from each other.
Judgement: If your understanding of scientific papers is limited, you might not be able to make an informed decision as to whether it is valid or if there are problems with the research. Is it difficult for a humanities student to critique a scientific paper in the same way that they would a piece of humanities research? Would there be a tendency to think something must be true because it’s science?
Aims of research: Further to this, should humanities use science as the basis of broad claims when often psychology papers usually describe small studies with limited sample sizes? On the other hand, having a different aim in approaching a study might mean that interesting ideas come out of it which wouldn’t otherwise be thought of.
A common example of non-scientists reading science papers is science in journalism. Although this has different aims and although the media often purposefully misinterprets science, some of the same problems are exemplified in regards to understanding and accessibility.
The scientific journal Nature even ran a news article with advice for scientists dealing with journalism, offering the perspective of the scientist trying to communiate with people outside the discipline. http://www.nature.com/news/dangerous-work-1.13861