Table 2 Experiment 2: Subjects’ vocal, nonvocal, and monitoring behavior at snake models is best explained by the receiver knowledge, not signaler habituation, hypothesis.

Experiment 2: Subjects’ vocal, nonvocal, and monitoring behavior at snake models is best explained by the receiver knowledge, not signaler habituation, hypothesis.. Subjects’ overall responses across all tests differed significantly across conditions (permutation test correcting for multiple testing: χ² = 62.47, P = 0.004). Parentheses denote the variable level that reflects the estimate when tested against the alternative level. GLMMs: H1 (receiver knowledge), supported or tentatively supported by models (B) to (H); H2 (signaler habituation), not supported by models (B) to (H). n = 10 subjects, 21 trials, and 12 dyads. Bold: P < 0.05; italic, P < 0.1. Test predictor for all models, experimental condition (rest hoo and alert hoo). Random factors for all models include subject identity, dyad identity of subject, and call provider. Binomial, models (B), (E), and (F); Gaussian, models (A), (C), (D), and (G) to (I). Model significance versus null model, effect size (marginal R²): (A) χ² = 10.31, df = 1, P = 0.006; R² = 0.16; (B) χ² = 6.7, df = 1, P = 0.009; (C) χ² = 3.12, df = 1, P = 0.077; R² = 0.30; (D) χ² = 3.96, df = 1, P = 0.046; R² = 0.32; (E) variable “alone” excluded due to model stability: χ² = 7.89, df = 1, P = 0.005; (F) χ² = 9.9, df = 1, P = 0.002; (G) χ² = 6.4, df = 1, P = 0.25; R² = 0.26; (H) χ² = 2.65, df = 1, P = 0.10; R² = 0.17; (I) χ² = 6.9, df = 1, P = 0.0085; R² = 0.41. For models (C) and (D), cases containing zeros were excluded; thus, P values are likely affected by low power (see Fig. 4, C and D, for paired data plots, table S2 for source data, and table S4 for additional analyses of control variables).