Cross-correlations of American baby names Paolo Baruccaa,1,2, Jacopo Rocchia,1, Enzo Marinaria,b, Giorgio Parisia,b,2, and Federico Ricci-Tersenghia,b aDipartimento di Fisica, Sapienza Universitá di Roma, I-00185 Rome, Italy; and bSezione di Roma 1, Istituto Nazionale di Fisica Nucleare, I-00185 Rome, Italy Contributed by Giorgio Parisi, April 27, 2015 (sent for review October 11, 2014; reviewed by R. Alexander Bentley) The quantitative description of cultural evolution is a challenging briefly describe them in the following lines. Compared with other task. The most difficult part of the problem is probably to find the relevant traits, neutral traits and, in particular, names appear appropriate measurable quantities that can make more quantita- very appropriate to study cultural changes, because the success of tive such evasive concepts as, for example, dynamics of cultural a name depends mainly on the influence that the surrounding movements, behavioral patterns, and traditions of the people. A culture wields on the parents of the newborns. Other traits suf- strategy to tackle this issue is to observe particular features of fer, for example, the influence of external forces, such as that due human activities, i.e., cultural traits, such as names given to to the producers, which may artificially shape the tastes of con- newborns. We study the names of babies born in the United sumers. This is particularly evident in the fashion market and in States from 1910 to 2012. Our analysis shows that groups of the music market (13). different correlated states naturally emerge in different epochs, The frequency distributions of names given to newborns have and we are able to follow and decrypt their evolution. Although fat tails, typical of many complex physical problems (14). Fat- these groups of states are stable across many decades, a sudden tailed distributions can be generated by different mechanisms (7, reorganization occurs in the last part of the 20th century. We 15, 16), and in the case of names they have been given several unambiguously demonstrate that cultural evolution of society can explanations. A scale-free network was used to study a fashion be observed and quantified by looking at cultural traits. We think diffusion process where each node could take one of many values that this kind of quantitative analysis can be possibly extended to (9), imitating “popular” nodes and avoiding “nonpopular” nodes. other cultural traits: Although databases covering more than one A stochastic model for cultural evolution has been proposed re- century (such as the one we used) are rare, the cultural evolution cently. Here names were chosen according to both individual on shorter timescales can be studied due to the fact that many preferences and social influence (10). These different mechanisms human activities are usually recorded in the present digital era. are all able to reproduce a fat-tailed distribution and were shown SOCIAL SCIENCES to reproduce several features of the real data. The popularity of a clustering | cultural evolution | cultural traits | complex systems name was also shown to be correlated with the popularity of similar names in previous years (13). Furthermore, names were ultural traits are behavioral patterns shared by the members analyzed in terms of activation and inhibition processes (17), to Cof social communities. Traditions, religions, beliefs, lan- explain their popularity. The rates of the rise and of the fall of the guage, and values are some examples. Far from being static and popularity of names were found to be correlated in refs. 11 and 18. isolated, they are continuously evolving and interacting with the The same phenomena are also being studied in the context of STATISTICS external environment, e.g., other communities and mass media, collective behavior (19, 20), where limited attention seems to play and they can be transmitted among members of communities on a crucial role (21, 22), and in the context of citation dynamics (23), timescales that are much shorter than those characterizing cul- where a universal temporal pattern is found. tural movements. Although changes in cultural movements may Some very interesting phenomena on the dynamics of Amer- occur over decades or centuries, changes in cultural traits may be ican baby names have been recently discussed in ref. 24, where observed from a daily to a yearly basis, depending on the trait. the authors introduced a new model for the choice of names. The An accurate analysis of existing, public data can teach a lot about their reciprocal influence. A cultural trait may promote or pre- Significance vent the popularity rise of others, a past cultural trait may have an influence on current and future ones, and finally the rise or fall of a cultural trait in a certain area may influence cultural Societal and cultural transformations are very general and traits in other areas. Cultural traits can be considered as the debated topics, both by scientists (e.g., sociologists) and by fundamental blocks of the culture of communities, and their public opinion (e.g., artists, music producers, brand manufac- evolution can be used to describe the evolution of society. turers, and advertising agencies). Although almost everyone Some of the most important progress in the understanding of would be able to express a position on such arguments, it is the evolutionary process of cultures is described in a number of much more difficult to support such an opinion based on sci- entific evidence. In this work we analyze the case of American texts that are at this point classic references: Among them are baby names and describe the evolution of tastes of parents refs. 1–3. Also many cultural traits have been studied in the past. regarding the choice of the name during the years of the last Among them are those that have negligible differences among century. Using quantitative methods we find that a deep each other, in terms of intrinsic costs and benefits, which are transformation occurred at the end of the 20th century and usually referred to as neutral traits. They play a special role in our suggest that this might be studied from a quantitative socio- study, as we explain below. Some of these traits are skirt lengths logical point of view. (4), pop songs (5), dog breeds (6), and pottery decorations in the archaeological record (7). Also keywords in academics vocabulary Author contributions: E.M., G.P., and F.R.-T. designed research; P.B. and J.R. performed have been the focus of recent interest (8). Data about names given research; P.B. and J.R. analyzed data; and P.B., J.R., E.M., G.P., and F.R.-T. wrote the paper. to newborns have been investigated for similar reasons (9, 10), and Reviewers included: R.A.B., Bristol University. they are the focus of our investigation. The authors declare no conflict of interest. Names come and go in society, as does any other cultural trait. 1P.B. and J.R. contributed equally to this work. Most of them have a popularity peak and then disappear. They 2To whom correspondence may be addressed. Email: [email protected] or carry important information on the transformation of the social [email protected]. structure (11, 12). Several quantitative approaches to analyze This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10. what can be learned from names have been proposed, and we 1073/pnas.1507143112/-/DCSupplemental. www.pnas.org/cgi/doi/10.1073/pnas.1507143112 PNAS | June 30, 2015 | vol. 112 | no. 26 | 7943–7947 Downloaded by guest on October 1, 2021 6 5 Montana 4 3 New York California 2 Jennifer / < > 1 0 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year Fig. 1. Number of newborns called Jennifer in the states of California, Montana, and New York, divided by its average values in these three states, as a functionoftime. model is defined in terms of a population of agents (babies), each not on the relations between local distributions of names in dif- of which holds a single variant (name), and where names of the ferent states of the United States (i.e., distributions in single new generations are given mainly by copying from the last gen- states). We believe that much can be learned, for example, from erations but also, sometimes, by inventing new names. Comparing the relations between local distributions of names in different real world data with the model in ref. 24 unveils a considerable states. Our main working hypothesis is that local changes of names increase in the innovation of names in the last part of the century. convey a large body of information on the mutual cultural in- This is consistent with the main findings of this paper, as we dis- fluences that communities (states) wield on each other. cuss further in the following. We focus our correlation analysis on different states of the The mechanisms behind the spreading of cultural traits are still United States during the 20th century. Statistics on names given to debated. The original hypothesis of Simmel (25) was that a fashion newborns in the United States can be downloaded from the arises because individuals of lower social status copy those of webpage of the US Social Security Administration (SSA) (27). perceived higher status. This is the idea used for the analysis done Different states have different popularity spreading curves for in ref. 9. This approach is different from the neutral model pro- each name (Fig. 1) (many of the common names rise and fade posed in ref. 26, where naming was considered in close connection with a very similar behavior). The overlap between these with the infinite-allele model of population genetics with a ran- curves could be used to describe the similarities between US dom genetic drift.