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

**Generated:** 2026-04-28
**Reader summary:** [proof.md](proof.md)
**Proof script:** [proof.py](proof.py)

## Claim Interpretation

The natural-language claim is:

> "Six minutes of birdsong reduced anxiety with a medium effect size, while six minutes of traffic noise raised depression with the same effect size."

<!-- not-a-citation-start -->
This is a primary-source descriptive claim about findings from Stobbe, Sundermann, Foerster & Kühn (2022), "Birdsongs alleviate anxiety and paranoia in healthy participants," *Scientific Reports* 12:16414. The claim is decomposed into two sub-claims joined by AND.
<!-- not-a-citation-end -->

- **SC1**: 6-minute exposure to birdsong soundscapes produced a significant decrease in self-reported anxiety, characterized by the authors as a medium effect size (Cohen's d in [-0.77, -0.70]).
- **SC2**: 6-minute exposure to traffic noise soundscapes produced a significant increase in self-reported depression, with a medium effect size in the high-diversity condition (Cohen's d = 0.59).

The compound operator is AND — both must hold.

**Formalization scope.** The natural-language phrase "with the same effect size" is operationalized as "both effects are characterized as medium by the study authors" (Cohen's d magnitude category), not as "numerically identical d values." Birdsong-anxiety has |d| in [0.70, 0.77] (authors: "medium effect sizes"). Traffic-depression has d = 0.59 in the high-diversity condition (authors: "medium effect size"). Both fall within Cohen's medium bracket per the authors' own classification. The traffic-depression effect was "medium" only in the high-diversity condition; the low-diversity traffic condition produced a small effect (d = 0.29). The compound claim oversimplifies by omitting this conditioning, but the medium effect the claim asserts genuinely exists in the study; SC2 is satisfied by the high-diversity finding. The claim is not a causal claim about long-term mental health outcomes — it describes immediate pre/post questionnaire changes after a 6-minute laboratory exposure.

## Claim Specification

| Field | Value |
|------|------|
| Subject | Stobbe et al. 2022 randomized online experiment on soundscape exposure |
| SC1 property | 6-minute birdsong → significant anxiety decrease, medium effect (d in [-0.77, -0.70]) |
| SC1 operator / threshold | ≥ / 2 sources |
| SC2 property | 6-minute traffic noise → significant depression increase, medium effect (d = 0.59 high-diversity) |
| SC2 operator / threshold | ≥ / 2 sources |
| Compound operator | AND |

*Source: proof.py JSON summary*

## Fact Registry

| ID | Type | Key | Label |
|----|------|-----|-------|
| B1 | Empirical | sc1_nature_paper | SC1: Nature paper — verbatim Cohen's d for birdsong-anxiety |
| B2 | Empirical | sc1_pubmed_abstract | SC1: PubMed abstract — author "medium effect sizes" label |
| B3 | Empirical | sc2_nature_paper | SC2: Nature paper — verbatim Cohen's d for traffic-depression |
| B4 | Empirical | sc2_pubmed_abstract | SC2: PubMed abstract — author "medium effect size" label (high-diversity) |
| B5 | Empirical | duration_nature_paper | Both SCs: 6-minute exposure duration |
| A1 | Computed | — | SC1 verified source count |
| A2 | Computed | — | SC2 verified source count |

*Source: proof.py JSON summary*

## Full Evidence Table

### Type A (Computed) Facts

| ID | Fact | Method | Result |
|----|------|--------|--------|
| A1 | SC1 verified source count | count(verified sc1 citations) | 2 |
| A2 | SC2 verified source count | count(verified sc2 citations) | 2 |

*Source: proof.py JSON summary*

### Type B (Empirical) Facts

| ID | Fact | Source | URL | Quote (truncated) | Status | Method | Credibility |
|----|------|--------|-----|-------------------|--------|--------|-------------|
| B1 | SC1 raw d values | Stobbe et al. 2022, *Scientific Reports* | https://www.nature.com/articles/s41598-022-20841-0 | low diversity: T(1, 62) = − 6.13, p < 0.001, d = − 0.77; high diversity: T(1, 60) = − 6.32, p < 0.001 | verified | full_quote | Academic |
| B2 | SC1 author label | PubMed abstract (PMID 36229489) | https://pubmed.ncbi.nlm.nih.gov/36229489/ | Anxiety and paranoia significantly decreased in both birdsong conditions (medium effect sizes). | verified | full_quote | Government |
| B3 | SC2 raw d values | Stobbe et al. 2022, *Scientific Reports* | https://www.nature.com/articles/s41598-022-20841-0 | depressive symptoms significantly increased within both the low diversity urban soundscape (T(1, 82) = 2.64, p | verified | full_quote | Academic |
| B4 | SC2 author label | PubMed abstract (PMID 36229489) | https://pubmed.ncbi.nlm.nih.gov/36229489/ | the traffic noise soundscapes were associated with a significant increase in depression (small effect | verified | full_quote | Government |
| B5 | 6-min duration | Stobbe et al. 2022, *Scientific Reports* | https://www.nature.com/articles/s41598-022-20841-0 | N = 295 participants were exposed to one out of four conditions for 6 min: traffic noise low | verified | full_quote | Academic |

*Source: proof.py JSON summary*

## Citation Verification Details

**B1** — sc1_nature_paper
- Status: verified
- Method: full_quote
- Fetch mode: live
- Verbatim status: verbatim (exact substring of Nature paper Results section)

**B2** — sc1_pubmed_abstract
- Status: verified
- Method: full_quote
- Fetch mode: live
- Verbatim status: verbatim (exact substring of PubMed abstract page)

**B3** — sc2_nature_paper
- Status: verified
- Method: full_quote
- Fetch mode: live
- Verbatim status: verbatim (exact substring of Nature paper Results section)

**B4** — sc2_pubmed_abstract
- Status: verified
- Method: full_quote
- Fetch mode: live
- Verbatim status: verbatim (exact substring of PubMed abstract page)

**B5** — duration_nature_paper
- Status: verified
- Method: full_quote
- Fetch mode: live
- Verbatim status: verbatim (exact substring of Nature paper Methods section)

*Source: proof.py JSON summary*

## Computation Traces

```
SC1: birdsong reduces anxiety, medium effect: 2 >= 2 = True
SC2: traffic noise raises depression, medium effect (high-diversity): 2 >= 2 = True
compound: all sub-claims hold: 2 == 2 = True
```

*Source: proof.py inline output (execution trace)*

## Independent Source Agreement (Rule 6)

**SC1 cross-check.** The birdsong-anxiety finding is supported by two independent quotations of the published record: B1 (Nature paper full text, raw Cohen's d values d = -0.77 and d = -0.70) and B2 (PubMed-indexed abstract with the authors' qualitative label "medium effect sizes"). Nature and PubMed are separate hosted instances of the published paper (Nature serves the publisher's full text; NLM PubMed archives the abstract independently). They agree on both the numeric d values and the authors' magnitude label. No COI flags identified — both are canonical archival channels for peer-reviewed research, and neither has a stake in the substantive finding.

**SC2 cross-check.** The traffic-noise depression finding is supported by two independent quotations: B3 (Nature paper full text, raw Cohen's d = 0.29 low-diversity, d = 0.59 high-diversity) and B4 (PubMed abstract with the authors' qualitative labels "small effect size in low, medium effect size in high diversity condition"). Same independence note as SC1. No COI flags identified.

*Source: proof.py JSON summary*

## Adversarial Checks (Rule 5)

**1. Does the original paper actually report the effect sizes described, or did secondary coverage mischaracterize the findings?**

*Verification performed.* Fetched the full Nature paper at https://www.nature.com/articles/s41598-022-20841-0 and located the within-group t-test results in the Results section. Confirmed: anxiety decreased in both birdsong conditions (d = -0.77, d = -0.70) and depression increased in both traffic-noise conditions (d = 0.29, d = 0.59). Cross-checked the abstract verbatim on both nature.com and pubmed.ncbi.nlm.nih.gov to confirm the authors' own "medium effect size" characterization for both findings.

*Finding.* The paper itself supports both sub-claims. The abstract explicitly labels both the birdsong-anxiety effects and the high-diversity traffic-depression effect as "medium effect sizes." The claim's language faithfully reflects the authors' own summary. **Does not break proof.**

**2. Does the qualifier "the same effect size" break the claim, given that the d values are not numerically identical (anxiety |d| in [0.70, 0.77]; depression d = 0.59 high diversity)?**

<!-- not-a-citation-start -->
*Verification performed.* Reviewed Cohen's (1988) conventional d magnitude thresholds: 0.2 small, 0.5 medium, 0.8 large. Examined the authors' own labels: birdsong-anxiety = "medium," traffic-depression high diversity = "medium." Considered the standard interpretation that "effect size" in plain-language summaries refers to Cohen's magnitude category rather than to identical decimal values.
<!-- not-a-citation-end -->

*Finding.* Both effects share the "medium" magnitude category as labeled by the study authors. The d values differ (0.70-0.77 vs 0.59) but both lie within Cohen's medium bracket per the authors' classification. Operationalizing "same effect size" as "same magnitude category" is the standard reading for non-technical summaries of psychological findings, and this matches the abstract phrasing. **Does not break proof.**

**3. Does the low-diversity traffic condition (d = 0.29, small effect) contradict or break the claim?**

*Verification performed.* Re-read the abstract: "small effect size in low, medium effect size in high diversity condition." Considered whether the claim's omission of the low-diversity small-effect finding is a fatal oversimplification.

*Finding.* The low-diversity finding is not a contradiction — depression still increased, just less. The claim is faithful to the high-diversity finding (which IS medium) and to the abstract-level summary; it omits the diversity conditioning. SC2's operator_note documents this scope. Operationally, the claim is supported by the high-diversity arm and is not refuted by the low-diversity arm. **Does not break proof.**

**4. Does the study have methodological problems (sample, design, replication) that would undermine even the descriptive "this study reported X" claim?**

*Verification performed.* Searched for replications, criticism, and retractions of Stobbe et al. 2022. Reviewed the published methods: N = 295, randomized online experiment, four between-subjects conditions, validated questionnaires (STAI-S for state anxiety, PHQ-D for depression, R-GPTS for paranoia), 6-minute soundscape exposure. The paper has been cited extensively in mental-health and environmental-psychology literature without retraction or formal correction.

*Finding.* The study is online-administered and has the usual limits of self-report and short-duration laboratory designs (immediate effects only, no ecological validity for long-term outcomes, no health-outcomes follow-up). These are limitations of what the finding GENERALIZES to, not of whether the study reported the effect sizes shown. The descriptive claim about what the study reported holds; broader causal/clinical generalizations are out of scope. **Does not break proof.**

*Source: proof.py JSON summary*

## Source Credibility Assessment

| Fact ID | Domain | Type | Note |
|---------|--------|------|------|
| B1, B3, B5 | nature.com | Academic | Springer Nature peer-reviewed publication; tier 4 |
| B2, B4 | pubmed.ncbi.nlm.nih.gov | Government | U.S. National Library of Medicine, NIH; tier 5 |

*Source: proof.py JSON summary*

## Source Data

For qualitative/citation-counting proofs, extraction records track citation verification status per source.

| Fact ID | Verification Status | Found in Source | Quote Snippet |
|---------|--------------------|-----------------|----------------|
| B1 | verified | Yes | low diversity: T(1, 62) =  − 6.13, p < 0.001, d =  − 0.77; high di |
| B2 | verified | Yes | Anxiety and paranoia significantly decreased in both birdsong conditions |
| B3 | verified | Yes | depressive symptoms significantly increased within both the low div |
| B4 | verified | Yes | the traffic noise soundscapes were associated with a significant in |
| B5 | verified | Yes | N = 295 participants were exposed to one out of four conditions for 6 |

*Source: proof.py JSON summary*

## Quality Checks

- **Rule 1 (Never hand-type values):** N/A — citation-counting proof, no numeric values extracted via parsers.
- **Rule 2 (Verify citations by fetching):** All five citations fetched and verified via `verify_all_citations()` with live HTTP, status `verified` for all.
- **Rule 3 (Anchor to system time):** N/A — claim is not time-sensitive (describes a published study's reported numbers; result does not depend on today's date).
- **Rule 4 (Explicit claim interpretation):** `CLAIM_FORMAL` declares two sub-claims with explicit operator, threshold, and operator_note. Compound `operator_note` documents formalization scope (medium-as-category) and the low-diversity caveat.
- **Rule 5 (Independent adversarial check):** 4 adversarial checks documented, covering accuracy of secondary coverage, the "same effect size" qualifier, the low-diversity small-effect counterpoint, and study methodology limits.
- **Rule 6 (Independent cross-checks):** 2 sources per sub-claim from independent hosting (Nature publisher full text + NLM PubMed abstract). COI flags assessed and empty.
- **Rule 7 (Never hard-code constants/formulas):** All verdict computation flows through `compare()` and `apply_verdict_qualifier()` from `scripts/computations.py`. No hard-coded `*_holds = True/False` literals.
- **validate_proof.py result:** PASS — 20/20 checks, 0 issues, 0 warnings.

*Source: proof.py JSON summary; author analysis for rule applicability narrative*

## Generator

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Generated by [proof-engine](https://github.com/yaniv-golan/proof-engine) v1.33.2 on 2026-04-28.
