My brain dump "Potential priority areas within cognitive sciences (psychology, neuroscience, and philosophy of mind)":

https://docs.google.com/document/d/12m_KDzKWfwQebrHGN4G4XCVIYPUHrm05Z6SB_loZr5w/edit

A lot of cause-specific research relates to these disciplines! I don't have a go-to list that answers your question directly as asked, but here are a few examples of resources that touch on this that might help to spark some ideas

• https://www.sentienceinstitute.org/research-agenda
• https://www.sentienceinstitute.org/podcast/episode-15.html
• https://forum.effectivealtruism.org/posts/LpkXtFXdsRd4rG8Kb/reducing-long-term-risks-from-malevolent-actors

Some quick thoughts (there is certainly already research on these but they seem important, and I don't know about reliability of existing research): 

• Scope insensitivity: e.g. why do people find it hard to care proportionally more about proportionally bigger things?
• Probabilistic reasoning: e.g. how can decision makers be ‘taught’ to take seriously low probability, high impact events?
• Decision-making under uncertainty: e.g. how can this be improved? Can be people be efficiently taught to become more bayesian?
• Group decision making: e.g. do more diverse groups really make better decisions?
• Meta: e.g. how can social science become more reliable?

80,000 Hours made a list of Research questions that could have a big social impact, organised by discipline. The disciplines include  psychology, cognitive science and neuroscience, economics, sociology, and some other potentially relevant disciplines.

Also, I made a central directory for open research questions, and many of the questions that can be found via that either are behavioural science questions or could inspire behavioural science questions. (The 80,000 Hours article drew on the directory, so it contains a more curated and organised-by-discipline selection from that, but the directory provides a larger total menu.) 

Great question! These are just some initial instincts - I'm not sure any of these questions are overly neglected, and they are too broad to be research questions, but curious to hear what others think:

• How can we [most effectively - implicit in all questions below] expand individuals' moral circles (including over temporal dimensions), particular during key choice points (e.g. choosing what to eat, whether/where to donate, what/who to vote for)?
• How can we improve political decision-making (i.e. ensuring political choices are consistent with individuals' values)?
• How can we improve judgement and decision-making under uncertainty (including deep uncertainty) more generally? And do these differ for individuals vs. small groups vs. large groups/organisations?
• How can we ensure individuals and groups behave more consistently with their decisions/intentions?
• How can we increase effective democratic behaviours more generally (i.e. behaviours outside of well-defined political decisions that are generally regarded to contribute towards a well-functioning democracy)?
• How can we increase cooperation between individuals and groups, particular individuals and groups that are distant (physically, temporally, socially, etc)?

I've proposed a number of things that I would love to see tested:
- Can we adapt Carl Rogers to real life? Inspire people to see ourselves in others (empathy), see the best in others (positive regard), and bring out the best in others.
- Can we expand Can Do attitudes? Can we put aside our doubts, do the work, and end up understanding, respecting, cooperating with, and bringing out the best in others in unexpected ways?
- Can we use our complex buying behaviors to foster empathy and positive regard? We buy different things, but we often have similar coveting, budgeting, browsing, shopping, and hoarding experiences. Can knowledge and sophistication in buying widgets help people build empathy and positive regard for people who buy doodads?
- Can exposing people to different kinds of biases  help them better understand different kinds of discrimination?
- Safe driving allows us to foster altruistic and cooperative behavior on a global scale. Can we expand it to general society?  Teach everyone to listen (instead of yield), check their biases (instead of the blind spots), reject Ideological Rage (instead of road rage).

More details here:
https://forum.effectivealtruism.org/posts/7srarHqktkHTBDYLq/bringing-out-the-best-in-humanity

How must we get systematically organized to alleviate suffering in the world?