Let me give an example. Rumor has it: train drivers annoyed by their relations with their manager of the schedule. Is it the persons? This is about psychology. Is it that their positions influence persons' behaviors? This is about sociology. Explanations :
Let's try psychology - "Those guys don't get along together well because their characters are incompatible" - Then, logic leads me to a resolution by the good will. I may ask people to water down a little bit, or I suggest to replace one of the persons, or both based on the assumption that the new person(s) will solve the problems.
However, do we need to appeal to psychology, while we may apply more direct an approach? Let's assume that relations are rooted in uncertainty anyone feels--and that people adopt strategies to deal with their uncertainties. We consider relationships between two people more like relationships of actors in the action system than personality interactions.
Train drivers, tired of being held in distant homes, consider rotations schedule in coming weeks their most painful uncertainty. Who manages this uncertainty? the manager of the schedule. The latter makes tedious, complex calculations every time they have to schedule a new service: should a train driver add his last minute requirement and it is a new painful calculation run. A balance of power. Note, this might be in a collaboration mode. It's up to the actors to choose.
A foreman, measured on the number of engines that come out of their assembly line, faces surprises that come from workshops upstream (insufficient production, incident delivery, ...). Lacking hierarchical power over their predecessors in the value chain, they play their personal power, yelling and/or threatening. The role makes it so--and foreman's psychology has to bear the pressure the role imposes.
Assumption. Relations between actors point out alliances and protections in a system.
Tool. Sociogram.
Experimentation. Develop a sociogram based on past interviews and make interviews for confirmation.
References knowing. Sociogram and action system according to Crozier & Friedberg
Stakeholder responsibility. Myself.
Relationships : System's responsibility
An approach as a sociologist rather than as a psychologist, what's the benefit to us?
The persons have not full control on changing themselves (psychologist's point of view), whereas they may work on their acting, they may modify, optimize it to a greater extent (sociologist's point of view). "Do not take it personal " takes on its full meaning here : it is your role, your acting that I'm challenging, not your person .
We see a relationship as an alliance or repulsion marker between two actors in the system rather than (dis-)agreement between two characters or two psychologies.
When does psychology contribute? Well, an individual's psychology supports this individual's acting. If a person replaces somebody in a given position, this person is likely to develop similar character traits because of the position pressure, provided that their personal psychology allows them.

Time for action
Draw a diagram on the people and the relationships among them. An given relationship gives an arrow. The more intense relationship, the thicker the arrow. Give a sign to the arrow, according to the emotions evoked by the person as to his relationship: "+" for a good relationship, "-" for a bad , and the double sign to mark a high intensity, if applicable ( "++" , etc . ).
In parallel, keep on interviews (three questions: what do you do, what is difficult, whom you work with). Meet people whom your contacts so far have talked about, whom they are related with. Prefer meet people closest to the ground first, often those whose position is at the bottom of the chart.
debriefing
Why prefer to start at the bottom of the scale of the organization?
1) for you to get to know the concrete problems
2 ) to obtain freer a speech
3 ) to collect objective information before getting to the management levels
Why wait for interviews before drawing the sociogram ?
What can we do with relationships in +/- , not really good or bad ?
Is it possible that a person's character be decisive in his acting ? Yes, if the position is difficult to cope with (pressure, uncertainty, personal attacks, destabilization), psychological resources are heavily used to hold the seat. However, strong psychological resources are necessary but insufficient.
Pascal. What should I do when I receive the formal prohibition to meet a particular person (the client, the principal investigator, etc.)? PM. Where does the ban comes from? Pascal. From the great stroumf. PM. High up, then. Pascal. Why is not meeting a stakeholder a problem? What should I bother? PM. Let's assume that a stakeholder has his foot on the brake; they may keep on the brake until you meet them. Pascal . Failing to meet a stakeholder would generate opposition later? PM . In this case, yes, an opposition. Pascal . Does the relationship between the sponsor and the forbidden stakeholder matter? PM . Say , if the sponsor has a bad relationship with the forbidden stakeholder, the initiative could be doomed. However, people involved in an action system stand failures provided that their gains outweight their pains. You'd be better inquire about those gains.
Gilles. I saw a newly appointed PM taking their assignment in Asia. They spent six weeks in meeting each of the stakeholders, including leaders and managers of project resources. PM. What was the project like? Gilles. It was to build an entire plant from bare land. PM. High stakes, I suppose. Gilles . Yes, indeed. And they took some time. PM. What did the final result look like? Gilles. Well, the project is a success; I have experience of similar projects, some are considered as major failures. PM. How do you think meeting with stakeholders, as did the PM, contributed to the performance? Gilles. As far as I know, they could count on stakeholders whenever it was needed. PM. As if meeting stakeholders makes them release the brakes? Gilles. You bet. Do they accelerate, afterwards? this is another story. But at least the brakes are released. PM. Meet people, release brakes. Gilles. This sounds like meeting people is giving them consideration. PM. How do you feel when a stranger asks you to commit to something? And how do you feel when, another scenario, the person takes the time to listen to you before asking for anything? Gilles. Very different scenarios, indeed. PM. So, what would you like to do now? Gilles. I'd like to meet with stakeholders before I have to ask them the tiniest thing.
The next step
When should you proceed to the next step ? When you've been around actors. For example, when you've already met people your interviewees claim they are related to.
The next step is to identify the uncertainty the system manages.