Language change involves the competition between alternative linguistic forms (1). Notably, the Spanish past subjunctive comes in two perfectly equivalent variants ended in -ra or -se (2 ); for instance, in the sentence 'If I were there', the verb can be equally translated to estuviera or estuviese. During a first spontaneous process that began in the Middle Ages, the form -ra migrated from the indicative to the subjunctive, displacing the original -se form (3-5) . A second period started with the creation of the Royal Spanish Academy in 1713, which produced a global standardization process that enforced the official spelling of -ra and -se as perfectly interchangeable variants ( 6) . Time series extracted from a massive corpus of books ( 7) show that this standardization produced a boost in the declining old form -se that eventually faded, leaving -ra  as the dominant one in the present time. The time series were successfully fitted by a low dimensional model that integrates two basic collective behaviors: an imitative component, and a fading of collective attention to the institutional regulation. We show that the natural scale over which collective attention fades is inversely proportional to the frequency of use of the verbs .
Language change involves the competition between alternative linguistic forms (1). When the forms evolve spontaneously, they either grow or decay monotonically (2 , 3). In the case of the Spanish past subjunctive, the evolution of its two competing forms (ended in -ra and -se) was perturbed by the appearance of the Royal Spanish Academy in 1713, which enforced the spelling of both forms as perfectly interchangeable variants ( 4) at a moment in which the -ra form was dominant (5) . Time series extracted from a massive corpus of books ( 6) reveal that this regulation in fact produced a renewed interest for the old form -se that eventually faded, leaving -ra again as the dominant one in the present day. We show that time series are successfully fitted by a two-dimensional linear model that integrates an imitative and a novelty component. The model reveals that the temporal scale over which collective attention fades is in inverse proportion to the verb frequency. The integration of the two basic mechanisms of imitation and attention to novelty allows to understand diverse competing objects, with lifetimes that range from hours for memes and news (7, 8) to decades for verbs. This suggests a general mechanism underlying cultural evolution .
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produced a global standardization process that enforced the official spelling of -ra and -se
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7) show that this standardization produced a boost in the declining
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time. The time series were
day. We show that time series are
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low dimensional
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two basic collective behaviors: an imitative component, and a fading of collective attention to the institutional regulation. We show that the natural
an imitative and a novelty component. The model reveals that the temporal
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inversely proportional to the frequency of use of the verbs
in inverse proportion to the verb frequency. The integration of the two basic mechanisms of imitation and attention to novelty allows to understand diverse competing objects, with lifetimes that range from hours for memes and news (7, 8) to decades for verbs. This suggests a general mechanism underlying cultural evolution