Hypothesis

Because disease risk falls with aridity, birds' baseline innate immune function would decline from the wet forest of southern Nigeria to the dry Sahel in the north.

What failed

Five innate immune indices measured in 286 Common Bulbuls sampled between 6 and 13°N did not decrease with aridity; only nitric oxide showed a weak curved pattern. At the resampled first site, several indices rose 12 weeks into the dry season, the opposite of expectation.

Broken assumption

Immune investment tracks environmental productivity in a simple, predictable way.

Why

The authors suggest that seasonal change within a site may influence immune function more strongly than spatial differences in aridity.

From the published paper: Nwaogu et al. Scientific Reports, 2020. ↗CC BY

Hypothesis

Higher urinary paraben concentrations would be associated with altered reproductive hormones and poorer semen quality in men, as animal studies suggested.

What failed

In men from an infertility clinic (hormones n = 167, semen n = 190), methyl and propyl paraben were not significantly associated with any outcome, and butyl paraben was not associated with hormones or conventional semen parameters; only a positive association of butyl paraben with sperm DNA damage was seen (p for trend = 0.03).

Broken assumption

Paraben exposure at everyday levels measurably affects men's reproductive hormones and semen quality.

Why

The authors found no evidence of a relationship with hormones or semen quality, and note that high within-person variability in paraben exposure across repeated urine samples and a modest sample size may have limited their ability to detect subtle effects.

From the published paper: Meeker et al. Environmental Health Perspectives, 2010. ↗Public domain

Hypothesis

Snowshoe hares facing shorter snow seasons would compensate for coat-colour mismatch through plasticity, by shifting moult timing with snow conditions or changing hiding, fleeing and resting behaviour when mismatched.

What failed

Observing nearly 200 hares at two Montana sites over a wide range of snow conditions, moult timing differed between sites but was largely fixed within each site, with only minimal response to snow during the spring moult. Hiding, fleeing and resting-spot choices showed no evidence of responding to mismatch; season, site and vegetation cover mattered more.

Broken assumption

Seasonally camouflaged animals can buffer climate-driven mismatch through flexible moult timing or behaviour.

Why

The authors conclude that moult and behavioural plasticity in this species are too limited to offset mismatch, so adaptation would need natural selection.

From the published paper: Zímová et al. Proceedings of the Royal Society B Biological Sciences, 2014. ↗CC BY

Hypothesis

Following an earlier BrainAGE study, musicians, and people with more musical training or active musical engagement, would have younger-looking brains than non-musicians.

What failed

In 125 scanned healthy adults, musician status was unrelated to BrainAGE score, and neither the musical-training nor the active-engagement subscale of the Gold-MSI predicted it; current physical activity did.

Broken assumption

Playing or engaging with music is enough on its own to make the brain look measurably younger.

Why

The abstract gives no explanation for the non-replication; the authors instead report that musical behaviours relate to a resilience factor.

From the published paper: Matziorinis et al. Brain Structure and Function, 2022. ↗CC BY

Hypothesis

Ingesting microplastics would impair the feeding and growth of Pacific oyster larvae.

What failed

Larvae readily ingested polystyrene particles from 70 nm to 20 μm, but exposure to 1 and 10 μm particles for up to 8 days had no significant effect on feeding or growth at under 100 microplastics per mL — concentrations above those observed in the sea.

Broken assumption

Ingesting microplastics at environmentally relevant or higher concentrations harms oyster larval feeding and growth in the short term.

Why

The paper reports no measurable effect on development or feeding over the study's duration; it does not propose a mechanism.

From the published paper: Cole et al. Environmental Science & Technology, 2015. ↗CC BY

Hypothesis

Adult queens touching pesticide residues in comb wax would suffer direct harm to their mass, sperm viability and reproductive performance, explaining links between wax residues and queen failure.

What failed

Six pesticides common in wax, alone and as a cocktail at 1–32 times typical wax concentrations, had no effect on queen mass, sperm viability or fat-body proteins in the lab. A field trial with the cocktail found no change in egg-laying pattern, queen mass, daughter-worker emergence mass or spermathecal proteins.

Broken assumption

Pesticide residues in wax harm queens through direct contact.

Why

The authors suggest earlier associations between wax residues and queen loss are more likely to arise indirectly, through effects on workers' care or perception of the queen.

From the published paper: McAfee et al. Scientific Reports, 2021. ↗CC BY

Hypothesis

Cerebellar stimulation should increase implicit, error-based visuomotor adaptation and prefrontal stimulation should facilitate explicit, strategy-based learning, dissociating the two mechanisms.

What failed

Cerebellar stimulation had no effect on target error or implicit learning in a horizontal adaptation task and only weak effects in a vertical one, while the prefrontal benefit found in the first experiment did not replicate in the second; inter-individual variability was high, with a few individuals driving the group effects, and task context alone (vertical against horizontal screen) changed performance and the implicit contribution.

Broken assumption

Stimulating a region selectively enhances the learning process attributed to it.

Why

The authors conclude the effects of each region are strongly context-dependent and not cleanly dissociable, and call for work on the sources of individual variability.

From the published paper: Liew et al. Frontiers in Neuroscience, 2018. ↗CC BY

Hypothesis

Because Registered Reports are preregistered and often share data and code, their main results should be independently reproducible from the shared materials.

What failed

Of 62 Registered Reports published 2014–2018, 41 had data and 37 had scripts available, 36 had both, 31 scripts would run, and the main results were reproduced for only 21 — 58% of those that shared both.

Broken assumption

Sharing data and analysis code is enough to make published analyses reproducible.

Why

The authors attribute the shortfall to data and code that are not shared, scripts that will not run, and data annotated too poorly to tell what variables and values mean, noting most researchers are not trained in computational reproducibility.

From the published paper: Obels et al. Advances in Methods and Practices in Psychological Science, 2020. ↗CC BY

Hypothesis

Approach-avoidance training, which had shown early promise for shifting implicit alcohol associations, and two new versions targeting implicit drinking identity, would change implicit associations and reduce drinking in US undergraduates.

What failed

Across two studies (300 social drinkers and 288 at-risk drinkers randomised to real or sham training in two sessions), none of the three training variants produced evidence of change in implicit alcohol associations or drinking outcomes; the only difference was a drop in drinking-refusal self-efficacy in one sham group.

Broken assumption

Two sessions of computerised approach-avoidance training are enough to shift implicit alcohol cognition and drinking in student drinkers.

Why

The authors conclude the training was ineffective at this dose in this population and suggest more severe populations, higher dose, combination with other treatment or more gamified tasks.

From the published paper: Lindgren et al. PLoS ONE, 2015. ↗CC BY