Speaking Science January 25, 2026 8 min read

The Science of "Um": Why Your Brain Betrays You in High-Stakes Speaking

You know the answer. You've prepared. You've practiced in the shower. Then you sit down for the interview, open your mouth, and...

"So, um, I think that, like, basically what I would say is, um..."

Sound familiar?

Here's the frustrating part: you're not stupid. You're not unprepared. Your brain is doing exactly what it's designed to do. It's just doing it at the worst possible moment.

Understanding why this happens is the first step to fixing it.

What's Actually Happening in Your Brain

When you speak, two systems in your brain are working simultaneously:

  1. The Planning System (Broca's area) - decides WHAT to say
  2. The Production System (motor cortex) - handles HOW to say it

In casual conversation, these systems work in perfect sync. You think, you speak. Seamless.

But in high-stakes situations - interviews, presentations, tests - something changes.

The Cognitive Overload Problem

Your brain is suddenly doing 5 things at once: processing the question, managing anxiety, monitoring the interviewer's reaction, constructing your answer, AND speaking. That's too many tasks for your working memory to handle smoothly.

When your planning system can't keep up with your production system, your brain needs to buy time. Its solution? Filler words.

"Um" and "uh" are your brain's way of saying: "Hold on, I'm still thinking."

The Two Types of Filler Words

Not all fillers are created equal. Research distinguishes between:

1. Hesitation Fillers ("um", "uh")

These signal you're searching for a word or idea. They're actually a sign that your brain is working hard.

When they happen: Mid-sentence, often before nouns or key concepts.

Example: "I managed the... um... the deployment pipeline."

2. Discourse Fillers ("like", "you know", "basically")

These are verbal habits. They don't serve a cognitive purpose - they're just patterns your mouth has learned.

When they happen: Beginning of sentences, between thoughts.

Example: "So basically, like, what we did was..."

23 Average filler words per minute for nervous speakers (vs. 5 for confident speakers)

The good news? Both types can be reduced. But they require different approaches.

Why Traditional Advice Fails

You've probably heard this advice before:

This advice is technically correct but practically useless. Here's why:

You can't consciously suppress fillers while also thinking about your answer.

Remember the cognitive overload problem? Asking someone to "just pause" adds another task to an already overloaded brain. It's like asking someone to juggle while also solving math problems.

The solution isn't conscious suppression. It's reducing the cognitive load in the first place.

Three Techniques That Actually Work

1. Pre-load Your Opening Phrases

The first 5 seconds of any answer are the hardest. Your brain is still processing the question while your mouth needs to start speaking.

Solution: Memorize 3-4 opening phrases that buy you thinking time WITHOUT sounding like fillers:

These phrases are on autopilot. Your mouth can say them while your brain plans the real answer.

2. Practice to Exhaustion (Seriously)

When an answer is in your long-term memory, it doesn't consume working memory. This frees up cognitive resources for smooth delivery.

The magic number? 5 repetitions minimum for any important answer.

By rep 5, you're not reciting - you've internalized it. Your brain can now focus on delivery instead of content.

3. Record, Count, Target One Filler

Awareness precedes change. But you can't fix everything at once.

The protocol:

  1. Record yourself answering a question
  2. Count your fillers (be honest)
  3. Identify your MOST frequent filler
  4. For the next week, focus ONLY on that one

Most people have a "signature filler" - maybe it's "like" or "basically" or "you know." Eliminating just one can reduce your total filler count by 40%.

Why This Works

Targeting one filler is cognitively manageable. Your brain can monitor for "basically" while still thinking about your answer. Trying to eliminate all fillers at once overwhelms the system.

The Uncomfortable Truth About Improvement

Here's what nobody tells you: reducing filler words feels weird at first.

When you pause instead of saying "um," the silence feels like an eternity. It isn't. Studies show listeners barely notice pauses under 2 seconds. But to you, it feels like you've stopped mid-sentence for an hour.

This discomfort is temporary. After a few weeks of practice, pauses feel natural. Fillers start to sound jarring.

The brain adapts. But only if you practice consistently.

What About Eliminating Fillers Completely?

You don't need to.

Research shows that a few fillers (2-4 per minute) actually make you sound more natural and relatable. Zero fillers can sound robotic or over-rehearsed.

The goal isn't perfection. It's control.

You want to choose when to pause, not have your brain force an "um" because it's overwhelmed.

A Note on Anxiety

Filler words and anxiety are closely linked. When cortisol (stress hormone) floods your system, it impairs working memory. This makes cognitive overload worse, which increases fillers.

Some people try to fix fillers by reducing anxiety. This is backwards.

Better approach: Practice until your answers are automatic. This reduces cognitive load, which reduces anxiety, which reduces fillers. The causation flows from preparation to confidence, not the other way around.

See Your Filler Words in Real-Time

Verborise counts your "um"s, "like"s, and "basically"s automatically. Record yourself, get instant feedback, and track your improvement over time.

Try Free - Count Your Fillers

The Bottom Line

Filler words aren't a character flaw. They're a symptom of cognitive overload - your brain trying to keep up with too many demands at once.

The fix isn't willpower. It's reducing the load:

Your brain isn't betraying you. It's doing its best with limited resources. Give it better resources, and the "um"s take care of themselves.

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