Publications

Robrecht van der Wel, Shaheed Azaad, Pernille Hemmer, John Michael (2026) · Preprint

In a recent meta-analysis, Mariano et al. (2025) conclude that people experience a stronger sense of agency over positive than negative outcomes, indexed by temporal compression. In this commentary, we evaluate that claim and identify several concerns about its robustness. First, we were unable to reproduce their main valence effect: our reconstruction of the three-level meta-analytic model yielded a smaller, non-significant difference. Second, we identified data integrity issues, including implausibly small standard deviations that appear to reflect computational errors. Third, we argue that temporal compression effects should be standardized before being combined, because values in milliseconds are not necessarily comparable across different paradigms. When we analyzed standardized effects, evidence for a valence effect was weak, and absent once adjusting for publication bias. Overall...

Shaheed Azaad (2026) · Preprint

Although power analysis has become increasingly accessible over time, researchers still find it challenging to compute power for complex ANOVA interactions. anovapowersim is an R package that enables users to easily specify between, within, and mixed interactions of varying complexity and simulate power based on a target effect size. This tutorial provides a short introduction to the package's core functionality, along with worked examples and sample R code.

Shaheed Azaad (2026) · Preprint

It is common and recommended practice in psychology to report standardised effect sizes alongside significance tests. As Cohen (1988) notes, the interpretation of these effect sizes as either small, medium, or large should depend on the field of research. The present study analysed 13,194 effects from 3,302 articles to empirically derive thresholds for social psychology (SP), individual differences psychology (IDP) and cognitive psychology (CP). Thresholds (in Pearson’s r) were smallest for SP (small: .17, medium: .24, large: .34), followed by IDP (small: .19, medium: .27, large: .41), while CP produced the largest effects (small: .24, medium: .34, large: .51). Thresholds for within-subjects designs (based on bias-corrected dz, or g) followed a different pattern: effects were smallest for IDP (small: 0.27, medium: 0.44, large: 0.78), slightly larger for SP (small: 0.33, medium: 0.49, la...

Shaheed Azaad, Yoshihisa Kashima, Nick Haslam (2026) · Preprint

Research has revealed considerable seasonal variation in human behaviour and emotion. However, whether cognitive performance is similarly seasonal remains an open question. While some studies have found a performance advantage in summer compared to winter, others have found either the reverse effect or no effect at all. Because demographics, locations, and cognitive domains of interest vary between studies, it is difficult to determine whether such heterogeneity reflects systematic variation due to study characteristics or whether significant findings are better explained by sampling variance and publication bias. In the present study, we tested for seasonality in 100,113 chess games played by 27,335 players. Not only did we not find a seasonal effect, but we also found no interactions with age, gender, the absolute latitude of the tournament location, and the human development index of...