Why Does AI “Lie”?—An Easy-to-Understand Explanation of the Hallucination Problem

Why Does AI “Lie”?

“That’s just AI making stuff up.”

“ChatGPT sometimes spouts ‘nonsense’ that sounds perfectly plausible.”
Haven’t you heard stories like that?

Actually, this is a phenomenon in AI known as “hallucination.”
Literally translated as “hallucination”—it means “stating something that isn’t true as if it were a fact.”

But why does this happen?
This guide explains what hallucinations really are, avoiding technical jargon as much as possible.

What exactly is hallucination?

Hallucination is when an AI “returns information that doesn’t actually exist, but presents it in a way that makes it sound plausible.”

For example…

Citing a research paper that doesn’t exist
Explaining a law that doesn’t exist
Talking about fictional companies or people as if they were “real”

Rather than saying the AI is lying, it’s more accurate to describe this as a state where it’s “confident despite not knowing.”

Why does hallucination occur?

There are two main causes.

① AI thinks in terms of “probability,” not “meaning”

AI (especially language models like ChatGPT) predicts the “next word” based on “probability.”
In other words, it’s simply imitating language patterns based on the idea, “If I say it like this, it’ll sound plausible, right?”

📌 For example, if asked, “What is XX?”, it’s natural to continue with, “XX is…”

However, the AI itself does not judge whether that content is factual or not.

② Limitations and Mix of Training Data

AI is trained on massive amounts of past text, but this includes…

Outdated information
Inaccurate information
Fiction (such as novels and movies).

In other words, for AI, “information that appears frequently online” may take priority.
The problem here is that the majority opinion isn’t necessarily the truth.

When Is This Most Likely to Happen?

Hallucinations are particularly likely to occur in the following situations:

Specialized topics (medicine, law, research, etc.)
Niche topics (topics the AI isn’t familiar with)
Ambiguous questions (lacking context)

If you find yourself thinking, “Is this really true?”, it’s very likely a hallucination.

How can you spot it? What can you do about it?

While it’s impossible to completely prevent hallucinations, the following measures are effective.

✅ Check the sources

Check whether there are sources for the information the AI has cited.
It’s especially important to verify the names of academic papers or laws by searching for them.

✅ Maintain a skeptical attitude, even when the AI seems confident

Even if the AI answers with confidence, it might just be “sounding convincing.”
Human intuition is still very important.

✅ Ask Specific Questions

Specifying specific dates or sources—such as “Is that from the Ministry of Health, Labor and Welfare’s 2024 announcement?”—can sometimes improve accuracy.

Conclusion | Finding the “Right Balance” with AI

If we understand that AI’s answers aren’t perfect,
we can skillfully use AI as a “consultant.”

AI is, after all, just a “smart suggestion-giver.”
When combined with human judgment, its power multiplies many times over.

That’s why it’s important to “be skeptical” and “not trust it too much” when interacting with AI.
And, ultimately, the final decision rests with “you” yourself.