The psychological reality of the learned "p < .05" boundary.

The .05 boundary within Null Hypothesis Statistical Testing (NHST) "has made a lot of people very angry and been widely regarded as a bad move" (to quote Douglas Adams). Here, we move past meta-scientific arguments and ask an empirical question: What is the psychological standing of the .05 boundary for statistical significance? We find that graduate students in the psychological sciences show a boundary effect when relating p-values across .05. We propose this psychological boundary is learned through statistical training in NHST and reading a scientific literature replete with "statistical significance". Consistent with this proposal, undergraduates do not show the same sensitivity to the .05 boundary. Additionally, the size of a graduate student's boundary effect is not associated with their explicit endorsement of questionable research practices. These findings suggest that training creates distortions in initial processing of p-values, but these might be dampened through scientific processes operating over longer timescales.

Relating Acoustic Measures to Listener Ratings of Children's Productions of Word-Initial /ɹ/ and /w/.

PURPOSE: The /ɹ/ productions of young children acquiring American English are highly variable and often inaccurate, with [w] as the most common substitution error. One acoustic indicator of the goodness of children's /ɹ/ productions is the difference between the frequency of the second formant (F2) and the third formant (F3), with a smaller F3-F2 difference being associated with a perceptually more adultlike /ɹ/. This study analyzed the effectiveness of automatically extracted F3-F2 differences in characterizing young children's productions of /ɹ/-/w/ in comparison with manually coded measurements. METHOD: Automated F3-F2 differences were extracted from productions of a variety of different /ɹ/- and /w/-initial words spoken by 3- to 4-year-old monolingual preschoolers (N = 117; 2,278 tokens in total). These automated measures were compared to ratings of the phoneme goodness of children's productions as rated by untrained adult listeners (n = 132) on a visual analog scale, as well as to narrow transcriptions of the production into four categories: [ɹ], [w], and two intermediate categories. RESULTS: Data visualizations show a weak relationship between automated F3-F2 differences with listener ratings and narrow transcriptions. Mixed-effects models suggest the automated F3-F2 difference only modestly predicts listener ratings (R 2 = .37) and narrow transcriptions (R 2 = .32). CONCLUSION: The weak relationship between automated F3-F2 difference and both listener ratings and narrow transcriptions suggests that these automated acoustic measures are of questionable reliability and utility in assessing preschool children's mastery of the /ɹ/-/w/ contrast.

Categorical Perception of p-Values.

Traditional statistics instruction emphasizes a .05 significance level for hypothesis tests. Here, we investigate the consequences of this training for researchers' mental representations of probabilities - whether .05 becomes a boundary, that is, a discontinuity of the mental number line, and alters their reasoning about p-values. Graduate students with statistical training (n = 25) viewed pairs of p-values and judged whether they were "similar" or "different." After controlling for several covariates, participants were more likely and faster to judge p-values as "different" when they crossed the .05 boundary (e.g., .046 vs. .052) compared to when they did not (e.g., .026 vs. .032). This result suggests a categorical perception-like effect for the processing of p-values. It may be a consequence of traditional statistical instruction creating a psychologically real divide between so-called statistical "significance" and "nonsignificance." Such a distortion is undesirable given modern approaches to statistical reasoning that de-emphasize dichotomizing the p-value continuum.