Shared ground found before a hard conversation, such as a background, a customer both served, or a problem both fought, makes the sponsor's proposal easier for the other person to hear.
An example
On tight urban sites, a general contractor's crane lifts were waiting days for planning sign-off, and a project executive wanted the company's safety director to accept a faster planning method. She had stopped two earlier proposals from project executives and was known to distrust anything sold on speed. Before the meeting he asked colleagues about her career. They had both worked, a decade apart, on the same hospital campus, and she had led the investigation after a near-miss there that he remembered from his first year. He opened with it: what he had seen as a junior engineer, and what he thought the investigation had got right. They spent twenty minutes on that site before turning to the proposal. She still asked for changes, including a second signature on lifts over a set weight, and agreed to a trial on two projects.
Why it works
People tend to like those who share their background, experience, or concerns, and they listen differently to people they like. A proposal that comes from someone the listener recognizes as similar in a way that matters looks better to them: they are more willing to hear it out and more generous in reading it. Common ground also gives the conversation a starting point both sides care about. The effect depends entirely on the similarity being real and relevant. Invented or trivial similarities get noticed, and they backfire.
The thinking behind it
Robert B. Cialdini Influence (1984) describes liking: people are more easily persuaded by those they like, and liking grows with similarity and genuine praise. In Harnessing the Science of Persuasion (2001), Cialdini's advice to managers is to uncover real similarities. A project executive and a safety director who discover a shared hospital campus and a near-miss both remember have found exactly such a similarity, and the proposal that follows is heard by someone more inclined to like its sponsor.
When it fits
Hard conversations with someone you do not know well, who has reason to be wary of you or your function, are where it helps, especially when the proposal will be heard better if the relationship comes first. It takes time to learn about the person, and an actual shared experience, customer, problem, or background worth talking about.
How to use it well
Do the homework. Ask colleagues about the person's career, read what they have written or presented internally, and look for real overlap: a site, a customer, a former employer, a problem you both fought.
- Pick the one shared thing that bears most on the proposal, and open with it briefly and specifically.
- Listen more than you talk while you are on it.
- Turn to the proposal without forcing a link between the two.
- Let the proposal stand on its merits from there.
Resist stretching a thin overlap into a bond. One honest connection, said plainly, does more than several decorative ones.
What it costs and where it backfires
Homework on a colleague can feel intrusive if they learn of it, so stick to what is generally known. A shared past can cut both ways: if your memory of the episode differs from theirs, you may open a disagreement. Common ground warms a conversation without settling it, and leaning on rapport to avoid hard questions will be noticed. Inventing a similarity, or feigning an interest you do not have, is flattery, and discovery costs you the relationship.
When it is used on you
Someone who opens a hard conversation with what you have in common may simply be doing it well. Enjoy it if it is real, then judge the proposal as you would anyone's, and ask yourself whether you would accept the same plan from a stranger. If the shared ground turns out to have been invented, weigh that against everything else they tell you.