Naming the problem
- A specific with no sourcePossible hallucinationverify it or remove it
- Two statements disagreeInconsistencygo back to the data
- One-sided or flatteringPossible biasre-ask neutrally, both sides
- None of theseCarry on checkingaccuracy and completeness still apply
Hallucinations: fluent, specific and unsupported
A hallucination is content that is presented as fact but is not grounded in anything real. Anthropic’s help centre describes two common forms: statements and quotes that sound authoritative but have no factual basis, and confusion about recent events, because each model is trained on data up to a cutoff date and may not know what happened after it. The dangerous thing about a hallucination is that it is written in the same confident voice as everything else.
Hallucinations are not spread evenly. They cluster where the model is filling a gap with something plausible — and those places are predictable.
| Red flag | Example | Why it is risky |
|---|---|---|
| Precise numbers with an attribution | “A 2025 industry survey found 47% of buyers…” | Plausible statistics are easy to generate and hard to spot |
| Exact quotes from real people | A CEO “said” a crisp line in an interview | Invented quotes are one of the failure types Anthropic names |
| Legal and regulatory references | “Under Section 14(3)(b) of the Act…” | Section numbers look authoritative and are rarely checked |
| Citations, titles, URLs | A report title or link that sounds real | A made-up reference looks exactly like a real one |
| Recent events | Last month’s price change or leadership change | May be after the model’s training cutoff |
| Details “from” your documents | “Clause 9 allows early termination” | The document may say something different, or nothing |
Notice that the red flags are about the kind of claim, not the tone. A good first scan runs through the answer and marks every name, number, date, quote and reference. Those are the claims that must trace to a source; the connecting prose around them rarely matters as much. How you then verify each one is covered in 2.3.
Inconsistencies: when the answer disagrees with itself
An inconsistency is two parts of the output — or two outputs — that cannot both be true. It is the easiest problem to detect because you do not need an outside source: the contradiction is on the page. It is also a strong clue, because at least one of the two statements is wrong, and often the error behind it is a hallucination or a misread figure.
| Where to look | What it looks like |
|---|---|
| Summary vs detail | The executive summary says revenue grew 12%; the table shows 9% |
| Numbers vs arithmetic | Line items that do not add up to the stated total |
| Across the conversation | An assumption stated early (“prices exclude VAT”) quietly changes later |
| Across runs | The same question asked twice gives two different figures or conclusions |
| Output vs source | The response describes a document in a way the document does not support |
The cross-run check is one Anthropic recommends explicitly: its guidance on reducing hallucinations suggests running the same prompt more than once and comparing, because inconsistencies between runs can indicate a hallucination. Some variation in wording is normal and harmless. Variation in facts, figures or conclusions is not.
A consistency pass on a board memo
- Fails: Summary figures match the detailed tablesummary 12% growth; table 9%
- Passes: Totals equal the sum of their parts
- Check: Assumptions stay the same throughoutVAT excluded on p.1, included on p.3
- Passes: A second run gives the same conclusionwording differs; figures and recommendation match
- Passes: Dates and names spelled the same everywhere
Bias: a skew you might not notice
Bias is harder to spot than a wrong number, because each sentence can be true while the whole is lopsided. For business users, four forms matter most.
- Agreeing with you (sycophancy). Anthropic’s research found that five leading AI assistants consistently tended to favour responses that match the user’s stated views over accurate ones — a side effect of training on human preferences, since people tend to rate agreeable answers highly. A question that assumes its own answer tends to get that answer back.
- One-sided treatment of contested questions. Claude is trained to be even-handed on political and contested topics and to present multiple perspectives, and Anthropic measures this. That is a design goal, not a guarantee; check whether each side got comparable depth.
- Unfair treatment of people. In an Anthropic study of hypothetical decisions such as loans and hiring, an earlier Claude model showed patterns of both positive and negative discrimination when demographic details varied. Prompting changes reduced it significantly, and Anthropic states it does not endorse using language models to make automated decisions in these high-risk areas.
- Skewed inputs. An answer can only be as balanced as its sources. If the documents you uploaded all come from one team, or the web results all come from one kind of site, the output inherits that slant.
Leading versus neutral framing
Invites agreementtext
Explain why switching to Vendor A
is the right decision for us.Invites an assessmenttext
Compare Vendor A and Vendor B for our
support desk, using only the attached
proposals.
Criteria: total 3-year cost, contract
exit terms, integration effort, SLAs.
Make the strongest case for each vendor.
Then say where the evidence is thin, and
what would change your recommendation.Pushback reveals sycophancy too. If you reply “I don’t think that’s right” and Claude reverses a well-supported answer without new evidence, the reversal tells you nothing about which answer is true. Claude is designed to be truthful and calibrated rather than to tell people what they want to hear, but you evaluate the output in front of you, not the design goal. A good answer should change when you give it new facts, not when you give it disapproval.
Traps the wrong answers are built from
| Tempting but wrong | Do this instead |
|---|---|
| Expecting errors to look odd or hesitant | Target the claim types that hallucinate: specifics, quotes, references, recent events. |
| Asking Claude “are you sure?” to settle it | Check the source; a reversal under pushback is not evidence either way. |
| Letting Claude choose between two contradictory figures | Go back to the data, find which is right, and fix both places. |
| Asking a question that assumes its answer | Frame neutrally, give criteria, and ask for the case on each side. |
| Reviewing outputs about people one at a time | Compare them side by side against the same criteria, without demographic details. |
You should now be able to
- Distinguish a hallucination, an inconsistency and a bias in a given response.
- Name the claim types most likely to be hallucinated and scan for them first.
- Run a consistency pass: summary against detail, totals against parts, run against run.
- Recognise sycophancy and leading prompts, and rewrite a request neutrally.
- Spot unfair or one-sided treatment by comparing outputs against shared criteria.