Reproducibility Project: only 36% of experiments replicate

The Open Science Collaboration repeated 100 classic experiments — results held in only 36–39% of cases. The beginning of the replication crisis.

The Open Science Collaboration, led by Brian Nosek from the Center for Open Science, united 270 researchers to replicate 100 experiments published in three top-tier journals: Psychological Science, Journal of Personality and Social Psychology, and Journal of Experimental Psychology: Learning, Memory, and Cognition.

The results were devastating: while 97% of original studies reported significant results (p < 0.05), only 36% of replications achieved statistical significance. Effect sizes in replications were, on average, half those of the originals.

The project triggered a deep debate about questionable research practices (QRPs): p-hacking, HARKing (hypothesizing after results are known), selective publication of positive results, and lack of methodological transparency.

The consequences were transformative: new pre-registration standards, the Registered Reports format, open data requirements, and a culture of direct replication. Psychology emerged as a leader in science reform.

Significance: This is one of the most significant developments in the psychology of our time. Its repercussions continue to be felt years later and have fundamentally changed how we understand the human mind and clinical practice.