Introduction There is an opinion that children absorb foreign languages like a sponge, which cannot be said about adults. The statement itself does not prove the existence of a critical period to start learning a foreign language. Nevertheless, it really is easier for children to master a second language that they hear around them (Gass et al., 2020). To prove the existence of a critical period for language learning, as well as to support this statement with quantitative data, modern scientists are conducting extensive research. One such study was the one in the article “A critical period for second language acquisition: Evidence from 2/3 million English speakers,” written by Joshua Hartshorne, Joshua Tenenbaum, and Steven Pinker. The original article appeared on pages 263-277 in issue 177 of Cognition in August 2018. The main problem discussed in the article is determining the evidence base for whether children do learn languages easier than adults. The authors also took it as their goal to find out the real reasons for the decline in language learning ability as we age. This article was chosen for analysis for several reasons. First, the topic of cognitive decline with age is a hot topic in the scientific community (Gass et al., 2020). Its research directly affects the development of understanding of the processes that occur in the human body. Second, the research presented in the article offers an unprecedentedly large sample for such a topic. This provides a solid evidence base for the conclusions proposed by the scientists. I will critically evaluate this article and consider its strengths and weaknesses in my analysis. This article is well-written, and the research it provides critically describes the age-related cognitive decline in humans. Article Summary The article’s main point is that the degradation of language learning ability with age is indeed provable. Nevertheless, the reasons for this phenomenon are hard to prove for practical and conceptual reasons. On the one hand, there is a paucity of research on this topic at the moment. On the other hand, measuring the final achievements of students who started at different ages cannot reveal changes in essential learning ability (Hartshorne et al., 2018). Another point of the article is that the breadth of the sample can compensate for the lack of data. That is why the authors undertook to process a data set unprecedented in the history of such research. The article’s main arguments are based on quantitative data analyzed during processing information collected from the sample patients. The authors argue that the irreversibility of language learning ability is confirmed by the fact that it steadily decreases with age. The methodology in this article stipulates the quantitative nature of the study. The authors of the study addressed the limitations by using a large data set, namely 669,498 native and non-native speakers of English (Hartshorne et al., 2018). They also used a computational model that estimates the trajectory of baseline learning ability by separating current age, age at first encounter, and years of experience. This allowed the authors to infer how the ability to learn grammar changes with age. They found that it persists until age 17 and then steadily declines. The authors state that this conclusion is proper for complex syntactic phenomena and those typically mastered in the early stages of language learning. The results confirm