Nobody likes giving negative feedback or delivering potentially disappointing news to a direct report. And while many individual contributors know that they actually need negative feedback to get better at their jobs, they typically don't relish the idea of finding out that they're falling short of expectations.

Nevertheless, negative feedback-- when delivered carefully and thoughtfully-- can help individuals and teams course correct, develop their skills, fortify their relationships, improve their impact on the business, and grow their careers. When delivered poorly, however, this feedback can create feelings of social rejection that are no different from feelings of physical pain in your brain.

One of the mistakes that managers make in delivering feedback (a mistake that is very simple to correct) is using what I call "assumption words". And there are two assumption words that people leaders use a lot, often without thinking about the impact:

Can't and Won't.

Let's look at these words in context, to see where the assumptions come into play:

"Josh, you have come into work after 9:30 A.M multiple times in the last three weeks, despite the fact that we start our workday at 9 a.m. You can't seem to get here on time."

Can't in this context assumes that Josh is unable to get into work at 9 a.m. But you don't know that, right? And, in fact, you probably believe he is able to do so, which is why you have the expectation to begin with.

Here's another example:

"Dana, I notice that when the client asks you a direct question, you won't look her in the eye."

Won't assumes that Dana is unwilling to make eye contact, and that this is a deliberate choice on her part. How do you know that she is actively refusing to do so? You don't.

And when you choose words that assume a certain inability or intentionality, you're possibly misrepresenting what's happening, and probably putting the other person on the defensive.

So, if can't and won't aren't the right words, what should you say instead?

Don't.

This word is a morally neutral, nonjudgmental, and more accurate way to describe what you're noticing. It's also more likely to open up the conversation so you can understand what's really getting in the way, rather than assuming you know what's behind the behavior.

Let's try that feedback again:

"Josh, you have come into work after 9:30 a.m multiple times in the last three weeks, despite the fact that we start our workday at 9 am. You don't seem to get here on time."

"Dana, I notice that when the client asks you a direct question, you don't look her in the eye."

No assumptions. No blame. Just observations.

Then, when you follow those clean, clear, direct statements with a clean, clear, direct inquiry (think "What's going on?" rather than "What's your problem?"), you are more likely to get a clean, clear, direct answer that leads to new insights and behaviors. And if you're going to assume anything, assume that your direct report is resourceful enough to grow, develop, and change.

As author Isaac Asimov put it, "Your assumptions are your windows on the world. Scrub them off every once in a while, or the light won't come in."