From Scorpion to Spider: Tracing the Origin of Fear of Spiders and Other Chelicerates through Perceptual Fear Generalization Gradients across Chelicerates

Introduction: In the current research, we tested similarity-based fear generalization by examining the scorpion-driven gradient (the structural signature of fear generalization) across Chelicerates. Our results supported the evidence that fear of spiders and other Chelicerates is largely generalized from scorpions.

Dataset: The data include fear of Chelicerates and other arthropods, relative and absolute similarity to spiders and scorpions, scorpion fear eliciting body parts, perceived danger, raters evaluations of Chelicerates shared body parts with scorpion, and province of residence.

Complementary analyses: A supplementary methodological manuscript containing confirmatory rank-order consistency analyses that extend the findings reported in the published article: From scorpion to spider: tracing the origin of fear of spiders and other chelicerates through perceptual fear generalization gradients across chelicerates
The preprint provides quantitative support for the individual-level alignment patterns discussed in the original work.
For the primary study findings, please cite the peer-reviewed article: This supplementary manuscript, which details extended rank-order consistency analyses, may be cited for its specific methodological contributions.

A confirmatory analysis on rank order consistencies
In a confirmatory analysis we applied Goodman and Kruskal’s Gamma, which evaluates ordinal rank consistency between variables. Because a similarity gradient requires higher similarity to be associated with higher fear (i.e., if Similarity₁ > Similarity₂ then Fear₁ ≥ Fear₂), Gamma provides a direct test of the monotonic ordering expected under a gradient account.
For the relative similarity task, chelicerates’ similarity to the scorpion showed a very strong monotonic association with fear ratings (γ = 0.929, p < 0.001). In contrast, similarity to the spider showed a weak negative association that was not statistically significant (γ = −0.407, p = 0.21), indicating no reliable ordinal consistency between spider similarity and fear.
For the absolute similarity task, the association was positive and statistically significant for scorpions (γ = 0.704, p = 0.026) but small and non‑significant for spiders (γ = 0.111, p = 0.80).
Importantly, this pattern remained when chelicerates were pooled with insects, where the spider‑similarity association remained non‑significant.
Taken together, these analyses provide further evidence for the fact that fear responses across Chelicerates follow a similarity‑based gradient anchored on scorpions.