:: COMPARE ::
The short answer
Same mechanism, opposite sign. The halo spreads one positive impression across unrelated traits; the horn spreads one negative impression the same way. Thorndike's 1920 data captured both directions in a single finding — the split into two names came later.
Side by side
| Aspect | Halo effect | Horn effect |
|---|---|---|
| Sign | Positive | Negative |
| Mechanism | Identical | Identical |
| Evidence base | A century of it | Thin |
| Named | 1920 | Later, informally |
What each one means
The halo effect is the tendency for one overall impression of a person or thing to bleed into your ratings of their specific, unrelated qualities — so someone judged good in general gets judged good at everything.
Full definition of Halo Effect →The horn effect is the tendency for one negative impression of a person to darken your judgment of their other, unrelated qualities — the halo effect running in reverse.
Full definition of Horn Effect →