# Proof Narrative: Six minutes of birdsong reduced anxiety with a medium effect size, while six minutes of traffic noise raised depression with the same effect size.

## Verdict

**Verdict: PROVED**

The claim accurately summarizes the published findings of a 2022 randomized online experiment, including the effect-size labels the study authors used in their own abstract.

## What Was Claimed?

The claim says that listening to six minutes of birdsong made people feel less anxious by a "medium" amount, and that listening to six minutes of city traffic noise made people feel more depressed by the same "medium" amount. This is the kind of plain-language summary that travels through press releases and headlines about how the soundscape around us affects mental state. It is worth checking because soundscape findings get repeated in popular coverage, and the claim could quietly drift away from what the original researchers actually reported.

## What Did We Find?

The claim traces back to a single study: Stobbe and colleagues, "Birdsongs alleviate anxiety and paranoia in healthy participants," published in *Scientific Reports* in October 2022. The study assigned 295 online participants at random to listen to one of four six-minute soundscapes — low-diversity birdsong, high-diversity birdsong, low-diversity traffic, or high-diversity traffic — and measured their anxiety and depression with standard questionnaires before and after.

For the birdsong conditions, anxiety dropped significantly in both. The published statistics show Cohen's d values of about 0.77 and 0.70, which the authors describe in their own abstract as "medium effect sizes." That phrase in the claim is not a journalist's gloss — it is the researchers' own label.

For the traffic-noise conditions, depression rose significantly in both. The Cohen's d was 0.29 in the low-diversity condition and 0.59 in the high-diversity condition. The authors describe this as a "small effect size in low, medium effect size in high diversity condition." So the "medium" label the claim uses for the traffic effect matches the high-diversity arm of the study.

Both findings — the birdsong effect on anxiety and the high-diversity traffic effect on depression — were verified verbatim against two independent sources: the full text of the paper hosted on Nature, and the abstract archived on PubMed by the U.S. National Library of Medicine. The numbers and the magnitude labels agree.

The claim's phrase "with the same effect size" describes a category, not a decimal. The two findings are not numerically identical — anxiety effects are slightly larger in absolute terms — but both sit inside the same "medium" bracket as classified by the study authors. Under the standard reading of plain-language summaries of psychological research, they are described as the same size.

## What Should You Keep In Mind?

A few caveats matter. The claim simplifies the traffic finding: depression also rose in the low-diversity traffic condition, but only with a small effect size (d = 0.29), not a medium one. The "medium" label only applies to the high-diversity traffic condition. The low-diversity finding does not contradict the claim, but the claim glosses over it.

The study measured immediate, short-term changes after a single six-minute exposure under online laboratory conditions. It does not say anything about whether long-term exposure to birdsong produces lasting anxiety relief, whether traffic noise causes clinical depression in real-world settings, or whether these effects matter for people with existing mental-health conditions. The descriptive claim — what this study reported — is supported. Broader claims that this proof does not address would need different evidence.

Cohen's d values of 0.70 and 0.77 are sometimes called "large" rather than "medium" by reviewers using strict cutoffs (0.5 medium, 0.8 large with midpoint thresholds at 0.65). The proof follows the study authors' own classification, which is what the claim mirrors. A reader who insists on strict cutoffs could reasonably classify the birdsong-anxiety effects as large, but that would not contradict the existence of the effect.

## How Was This Verified?

Five quotes from the original publication and its NLM-archived abstract were fetched and matched character-by-character against the live source pages. The reasoning chain is laid out in [the structured proof report](proof.md), with adversarial checks and credibility details available in [the full verification audit](proof_audit.md). To check this yourself, you can [re-run the proof yourself](proof.py).
