title: Dominant words rise to the top by positive frequency-dependent selection.

authors: Pagel, Mark

subjects: approximate Bayesian computation

abstract: A puzzle of language is how speakers come to use the same words for particular meanings, given that there are often many competing alternatives (e.g., "sofa," "couch," "settee"), and there is seldom a necessary connection between a word and its meaning. The well-known process of random drift-roughly corresponding in this context to "say what you hear"-can cause the frequencies of alternative words to fluctuate over time, and it is even possible for one of the words to replace all others, without any form of selection being involved. However, is drift alone an adequate explanation of a shared vocabulary? Darwin thought not. Here, we apply models of neutral drift, directional selection, and positive frequency-dependent selection to explain over 417,000 word-use choices for 418 meanings in two natural populations of speakers. We find that neutral drift does not in general explain word use. Instead, some form of selection governs word choice in over 91% of the meanings we studied. In cases where one word dominates all others for a particular meaning-such as is typical of the words in the core lexicon of a language-word choice is guided by positive frequency-dependent selection-a bias that makes speakers disproportionately likely to use the words that most others use. This bias grants an increasing advantage to the common form as it becomes more popular and provides a mechanism to explain how a shared vocabulary can spontaneously self-organize and then be maintained for centuries or even millennia, despite new words continually entering the lexicon.

text: Dominant words rise to the top by positive frequency-dependent selection. A puzzle of language is how speakers come to use the same words for particular meanings, given that there are often many competing alternatives (e.g., "sofa," "couch," "settee"), and there is seldom a necessary connection between a word and its meaning. The well-known process of random drift-roughly corresponding in this context to "say what you hear"-can cause the frequencies of alternative words to fluctuate over time, and it is even possible for one of the words to replace all others, without any form of selection being involved. However, is drift alone an adequate explanation of a shared vocabulary? Darwin thought not. Here, we apply models of neutral drift, directional selection, and positive frequency-dependent selection to explain over 417,000 word-use choices for 418 meanings in two natural populations of speakers. We find that neutral drift does not in general explain word use. Instead, some form of selection governs word choice in over 91% of the meanings we studied. In cases where one word dominates all others for a particular meaning-such as is typical of the words in the core lexicon of a language-word choice is guided by positive frequency-dependent selection-a bias that makes speakers disproportionately likely to use the words that most others use. This bias grants an increasing advantage to the common form as it becomes more popular and provides a mechanism to explain how a shared vocabulary can spontaneously self-organize and then be maintained for centuries or even millennia, despite new words continually entering the lexicon.

year: 2019

title: Volcanology and secondary alteration of the 1.6 Ma Ngaroma Ignimbrite, Upper Waipari Valley

authors: Ross, ChrisAnne

subjects: Taupo Volcanic Zone (TVZ)

abstract: The 1.6 Ma Ngaroma eruption from the Mangakino Volcanic Centre (MVC) is the first known rhyolitic event of the Taupo Volcanic Zone (TVZ), and variations of primary components recorded throughout the Ngaroma Ignimbrite provide insight(s) into pre-eruptive processes and post-emplacement mechanisms.

A field study of the Ngaroma Ignimbrite was undertaken proximal to the source caldera (~25 km) around the township of Ngaroma. Two primary facies (a lithic- rich and lithic-poor facies) and four subfacies have been identified and are presented in four stratigraphic logs, which vary both vertically and laterally throughout the field area. The facies reflect syn- and post-deposition process that are identifiable from one another based on macroscopic observations including changes in primary componentry, the degree of welding and nature of secondary alteration. Variations in depositional structures and textures highlight the intense welding, limited incorporation of vent-derived lithics, and the absence of a pumice/ash fall deposit underlying the ignimbrite, which suggest that the parent pyroclastic flow formed from the immediate collapse of a highly explosive, caldera-forming eruption column.
Petrographic observations and mineralogic analyses involving optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) record high concentrations of sanidine and cristobalite, followed by clay minerals (kaolinite), which suggest the deposit endured significant post-emplacement processes such as vapour-phase alteration and devitrification. The ignimbrite matrix varies from a eutaxitic texture comprising (a) visible, well-formed, but devitrified, glass shards typically 300 to 800 μm, to (b) a fine-grained, homogenous, optically unresolvable medium; the latter can be resolved under SEM and comprises intergrown <3 μm- sized K-feldspar (sanidine), amorphous/nano-crystalline silica (cristobalite ± tridymite), and pore cavities.

Geochemical analyses of major and trace elements on bulk ignimbrite and pumice were determined using x-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and on individual minerals by electron microprobe analysis (EPMA). Samples used in these geochemical analyses have been pervasively altered, and that due to the lack or absence of primary material (fresh glass and pumice), some of the patterns observed here are presumed to in part reflect post alteration processes (vapour-phase alteration and devitrification) and therefore, are of limited use for understanding primary magmatic processes. The major and selective trace elements of bulk rock ignimbrite and pumice confirm a rhyolitic composition and are consistent with the effect of syn- and post-emplacement alteration processes. Geochemical signatures of rare earth elements (REE) observed on multielement diagrams are associated with subduction related magmas and indicative of crustal contamination. Major element compositions of both feldspar and pyroxene phenocrysts range from An₁₅₋ An₂₈ and Or₅₋Or₁₂ and from En₃₂ to En₄₁, respectively, and are typical composition of rhyolitic magmas.

text: Volcanology and secondary alteration of the 1.6 Ma Ngaroma Ignimbrite, Upper Waipari Valley The 1.6 Ma Ngaroma eruption from the Mangakino Volcanic Centre (MVC) is the first known rhyolitic event of the Taupo Volcanic Zone (TVZ), and variations of primary components recorded throughout the Ngaroma Ignimbrite provide insight(s) into pre-eruptive processes and post-emplacement mechanisms.

A field study of the Ngaroma Ignimbrite was undertaken proximal to the source caldera (~25 km) around the township of Ngaroma. Two primary facies (a lithic- rich and lithic-poor facies) and four subfacies have been identified and are presented in four stratigraphic logs, which vary both vertically and laterally throughout the field area. The facies reflect syn- and post-deposition process that are identifiable from one another based on macroscopic observations including changes in primary componentry, the degree of welding and nature of secondary alteration. Variations in depositional structures and textures highlight the intense welding, limited incorporation of vent-derived lithics, and the absence of a pumice/ash fall deposit underlying the ignimbrite, which suggest that the parent pyroclastic flow formed from the immediate collapse of a highly explosive, caldera-forming eruption column.
Petrographic observations and mineralogic analyses involving optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD) record high concentrations of sanidine and cristobalite, followed by clay minerals (kaolinite), which suggest the deposit endured significant post-emplacement processes such as vapour-phase alteration and devitrification. The ignimbrite matrix varies from a eutaxitic texture comprising (a) visible, well-formed, but devitrified, glass shards typically 300 to 800 μm, to (b) a fine-grained, homogenous, optically unresolvable medium; the latter can be resolved under SEM and comprises intergrown <3 μm- sized K-feldspar (sanidine), amorphous/nano-crystalline silica (cristobalite ± tridymite), and pore cavities.

Geochemical analyses of major and trace elements on bulk ignimbrite and pumice were determined using x-ray fluorescence (XRF) spectrometry and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), and on individual minerals by electron microprobe analysis (EPMA). Samples used in these geochemical analyses have been pervasively altered, and that due to the lack or absence of primary material (fresh glass and pumice), some of the patterns observed here are presumed to in part reflect post alteration processes (vapour-phase alteration and devitrification) and therefore, are of limited use for understanding primary magmatic processes. The major and selective trace elements of bulk rock ignimbrite and pumice confirm a rhyolitic composition and are consistent with the effect of syn- and post-emplacement alteration processes. Geochemical signatures of rare earth elements (REE) observed on multielement diagrams are associated with subduction related magmas and indicative of crustal contamination. Major element compositions of both feldspar and pyroxene phenocrysts range from An₁₅₋ An₂₈ and Or₅₋Or₁₂ and from En₃₂ to En₄₁, respectively, and are typical composition of rhyolitic magmas.

year: 2020

title: Recognition and indigenizing official statistics: Reflections from Aotearoa New Zealand and Australia

authors: Kukutai, Tahu

subjects: Indigenou

abstract: In First World colonised nations such as Aotearoa New Zealand and Australia, population statistics form the evidentiary base for how Indigenous peoples are known and `managed' through state policy approaches. Yet, population statistics are not a neutral counting. Decisions of what and how to count reflect particular assumptions about Indigenous identity, ways of life and wellbeing. More often than not, the requirements and priorities of government take precedence over the informational needs and priorities of Indigenous communities. Whereas National Statistics Offices (NSOs) once rendered Indigenous peoples invisible in official statistics through non-recognition, the more pressing problem in the 21st century is that of misrecognition. In seeking to move beyond statistical misrecognition, we propose a set of guiding principles for bringing government reporting frameworks and Indigenous concepts of identity and wellbeing into closer proximity. We argue that a principled approach to collecting, disseminating and analysing Indigenous data not only avoids misrecognising Indigenous peoples but enhances the functionality of official statistics for Indigenous peoples and NSOs alike.

text: Recognition and indigenizing official statistics: Reflections from Aotearoa New Zealand and Australia In First World colonised nations such as Aotearoa New Zealand and Australia, population statistics form the evidentiary base for how Indigenous peoples are known and `managed' through state policy approaches. Yet, population statistics are not a neutral counting. Decisions of what and how to count reflect particular assumptions about Indigenous identity, ways of life and wellbeing. More often than not, the requirements and priorities of government take precedence over the informational needs and priorities of Indigenous communities. Whereas National Statistics Offices (NSOs) once rendered Indigenous peoples invisible in official statistics through non-recognition, the more pressing problem in the 21st century is that of misrecognition. In seeking to move beyond statistical misrecognition, we propose a set of guiding principles for bringing government reporting frameworks and Indigenous concepts of identity and wellbeing into closer proximity. We argue that a principled approach to collecting, disseminating and analysing Indigenous data not only avoids misrecognising Indigenous peoples but enhances the functionality of official statistics for Indigenous peoples and NSOs alike.

year: 2015