John Kingston - US grants

The central hypothesis of this proposal is that some articulations covary in distinctive features and segments because their acoustic effects are integrated in perception, rather than because those articulations are yoked to each other physiologically. this hypothesis will be tested using two paradigms designed to assess perceptual integration of orthogonal stimulus dimensions: the Garner (1974) paradigm to assess integration among a variety of articulatory covariates in vowel height and [voice] contrasts, and the Nearey (1990) paradigm to assess integration of redundant with distinctive features in labial consonants. This set of experiments focuses on selected contrasts, but investigates each of them comprehensively. If integration can be demonstrated among the acoustic effects of the covarying articulations in these distinctive features and segments, then this aspect of the listener's response to speech signals contributes substantially to reducing the degrees of articulatory freedom allowed the speaker, by selecting those articulatory aggregates that best serve the integrative perceptual mechanisms in the listener. Among other things, this result implies that the acquisition or remediation of articulatory control would be best served by a demanding rather than tolerant listener.

The general topic of this dissertation is sonority. Specifically, the following issues will be addressed: (1) What is sonority? (2) What is the articulatory, acoustic, and/or auditory basis of sonority? (3) How should sonority be quantified? (4) Is the sonority scale universal or language-specific? and (5) What role should sonority play in formal phonological constraints?

It has long been recognized that sonority differences determine the sequencing of sounds within syllables, a pattern observed in all languages. In order to explain this universal effect, many linguists have suggested that sonority derives from differences in how sounds are pronounced or perceived. However, to date a phonetic definition of sonority (in articulatory, acoustic, or perceptual terms) has remained elusive. Consequently, a number of phonologists and phoneticians have questioned the theoretical validity of sonority altogether, claiming that this notion is impossible to characterize in a concrete way. Consequently, the potential contribution of this project is to resolve a long-standing controversy regarding the physical basis of sonority.

The goal of this project is to determine which of five physical parameters best characterizes sonority differences: intensity (loudness), peak rate of oral air flow, peak intraoral air pressure, constriction duration, or frequency of the first formant. Each of these characteristics will be systematically studied in the speech of multiple native speakers of both English and Spanish for all language-specific phonemes, consonants and vowels alike. The objective of this research is to demonstrate that sonority can be quantified in a precise, consistent, non-arbitrary, and phonetically-grounded way based on the values of one or more of these physical correlates.

Historically, Tanzania has served as a major source for evidence into the evolution of humankind. In the relatively unexplored southwestern portion of the country, the Rukwa Basin presents favorable conditions for the preservation and recovery of primate fossil remains. The current project will be a survey and reconnaissance of this area to collect paleontological, and geological, samples relevant to human evolution from this relatively unexamined area.

The Rukwa Basin is a northwest trending rift roughly 300km by 50km. Geologic surveys have identified four major stratigraphic units with the most relevant being the Lake Bed deposits dated roughly 10 -- 0.1 million years ago. The objectives of the project are as follows 1) survey of the Rukwa Basin; 2) collection of hominin fossils; 3) collection of other fossils, and geological specimens, relevant to dating of the area, or reconstruction of the paleoenvironment.

Human origin studies have thrived in the past few decades from a variety of advances in analytical approach, or from the application of technology including medical imaging techniques such as computed tomography (CT). Few advances, however, have as dramatic and immediate an impact as the announcement of new fossil finds. The past decade alone has seen one new genus and several new species of early hominin described. Equally important are reports expanding the known geographic distribution of some species (e.g., Australopithecus boisei in Ethiopia; Homo rudolfensis in Malawi). The proposed survey of the Rukwa basin hopes to add to the early hominin database by discovering new fossils and/or increasing the understanding of the ecological circumstances of human evolution.

DESCRIPTION: (provided by applicant): In fluent speech, speakers begin to pronounce the next sound before they're done pronouncing the last. As a result, speech sounds not only occur right next to one another but actually overlap, and pauses only occur between whole phrases and not individual sounds. This characteristic of fluent speech presents the listener with two formidable problems: separating overlapping sounds and then recognizing sounds whose acoustics have been distorted by the overlap with its neighbors' pronunciations. This proposal pursues the hypothesis that both separation and recognition can happen because successive intervals in the signal contrast with one another perceptually. For example, after an interval in which most of the sound energy is at high frequencies, a sound whose energy is at mid frequencies will sound relatively low, or after a relatively long interval, an interval of intermediate duration will sound relatively short. The experiments test a version of this hypothesis in which sequential contrast is exaggerated like this in the initial auditory evaluation of the sounds, before the listener has assigned any linguistic value to the sound, i.e. before the sounds are recognized as instances of particular categories. If sequential contrast arises before the sounds are recognized, then it will be impervious to any linguistic knowledge the listener may have, e.g. of whether the current sound makes a word with its context, occurs frequently in that context, is phonotactically legal in that context, etc. A separate, prelinguistic, auditory stage of phonetic processing is diagnosed by better discrimination of sound sequences that differ in the direction of their sequential contrast, e.g. high-low vs low-high, than of sequences that don't, i.e. high-high vs low-low. If linguistic knowledge is used at all stages of processing, these two pairs of sequences should instead be equally easy to distinguish because all the intervals will have been assigned to categories and will therefore be equally different. The results of these experiments therefore permit a choice between interactive models of speech sound recognition in which listeners use their linguistic knowledge at all stages in processing the speech sounds they hear and autonomous models in which they use only the psychoacoustic properties of the signal during the first stage, and only later apply what they know linguistically to the output of that stage. If the autonomous model is supported, then the robustness of speech perception under adverse conditions or by impaired listeners can be improved more by enhancing signal quality than adding redundant linguistic information.

Exploring the course of human evolution extends beyond the discovery and description of the fossils of early humans. To understand the evolutionary processes that led to key human features such as upright walking, a large brain, tool manufacture and use, and behavioral flexibility, it is necessary to develop a context for these innovations. What were the environmental forces that shaped and directed human evolution? Human evolution is a consequence of the interactions of early hominids with their physical and biological surroundings and there is a need to specifically reconstruct these parameters in association with discoveries of hominids. Documenting paleoenvironments at a relevant scale in the terrestrial record and developing causal links between evolution and environmental change, however, remains difficult. As a result, aspects of human evolution have been interpreted in the context of environmental data from the marine record, which provide a detailed record of large scale climatic change. This approach is valid only if links between global or regional phenomena and specific shifts in local hominid ecosystems can be demonstrated.
This proposal seeks to address directly these issues by examining a series of environmental indicators to develop a high-resolution paleoenvironmental framework for a hominid-bearing sequence in the East African Rift Valley. This can then be linked to global climate changes. The work has at its focus a 2-3 million year old sedimentary sequence exposed in the Tugen Hills, a fault block within the rift valley near Lake Baringo in Kenya. This sequence exhibits abrupt and repeated cycling of major freshwater lake systems reflecting fluctuating climatic conditions. In recent research, this project has established a clear link between these short term oscillations (every 23 thousand yrs) and Milankovitch cycles that result from variations in the solar radiation received at the top of the atmosphere, controlled by variations in the geometry of the earth''s orbit. These changes represent the major driving force in the earth climate system through time, including glacial-interglacial cycles. Thirty-six vertebrate fossil localities, including three hominid sites, can be linked directly to this sequence, providing an opportunity to establish patterns of response by animals and vegetation to these short term shifts.
This research represents the first attempt to develop multiple environmental and ecological indicators that can be linked directly to Milankovitch cycling in a terrestrial rift valley context. These data will be used to generate insights into the evolutionary response of hominid ecosystems to these pervasive climatic oscillations over the last six million years in Africa. While these data relate directly to fossil hominids and their vertebrate communities in the Baringo Basin, linking local ecological shifts with orbitally-forced patterns of insolation affords the prospect of extrapolating the affects of climatic oscillations on terrestrial ecosystems regionally in the past. With these data, we can begin to formulate high-resolution models for interpreting correlations between climate and human evolution, and elucidate the role of environmental change as a potential driving force in mammalian evolution in general and human evolution in particular. This research will foster highly interdisciplinary and collaborative studies, essential in developing perspectives of the multi-dimensional links between evolution and ecology. The project outlined here represents an ideal forum in which to generate and integrate research ideas cutting across traditionally disparate academic disciplines. The study will broaden opportunities and enable the participation of graduate students as well as research personnel from the National Museums of Kenya.

Evolutionary processes occurring within the last 3 million years of the hominin lineage have been intimately associated with diet. Dietary factors hypothesized to have played critical roles in the niche partitioning between australopithecines, paranthropines, and early Homo include variable contributions of seeds, tubers, ripe or unripe fruit, pith, and animal flesh. Current approaches, however, lack the necessary resolution for differentiating the dietary contribution of these items within fossil species. Isotopic approaches represent one methodology with the potential of quantitatively estimating the contribution of individual food stuffs within a given dietary niche. As the tissues of an organism are constructed from dietary components ingested from the environment, the isotopic composition of the individual reflect these inputs. However, to interpret tissue level isotopic variation in relation to individual diet, one must understand the underlying isotopic variability within the lived environment.

The goal of this project is to utilize compound specific isotopic analyses of individual amino acids to reveal how isotopic variability within the diet of chimpanzees is consumed, metabolized, and deposited within the hard tissues. Incorporating elements of primatology, biogeochemistry, and nutritional science this project will examine amino acid delta13C and delta15N variability within the environment and the subsequent physiological routing from diet to hair, bone and teeth of modern chimpanzees in Kibale National Forest, Uganda. Intellectual merit: These analyses represent a novel and significant approach to improve our understanding of isotopic variability within modern East African C3 ecosystems and chimpanzee physiology. Additionally, they will provide the groundwork necessary for high-resolution dietary reconstruction from fossil remains of our earliest hominin ancestors. Broader impacts: The ability to quantify past consumption and thereby elucidate the role of foods over the course of human evolution is critically important for making informed decisions about how humans should healthfully, sustainably, and ethically consume into the future. This research will contribute to the doctoral dissertation and academic training of a graduate student.

Our knowledge of the sound patterns in a language plays a key role in determining our perception of incoming speech. An important question for an accurate model of speech perception is how the auditory system and our knowledge of sound patterns interact. Do we first use our auditory system to perceive speech just like any other type of sound, and then later bring our knowledge of sound patterns found in the language to bear on it? Or do we apply our knowledge of the sound patterns immediately? According to the first view, the working of the auditory system itself cannot be influenced by our knowledge of linguistic patterns, but on the second view, it can.

Under the direction of Dr. John Kingston, Mr. Michael Key will conduct identification and discrimination studies, as well as a priming experiment that measures certain potentials of the brain's electrical response, in order to investigate these questions. This dissertation research will assess whether the behavior associated with knowledge of a sound pattern corresponds to the activity of relatively late electrical activity in the brain, or whether it is also reflected in relatively early brain activity. Converging evidence from these various techniques bear directly on questions regarding the architecture of speech perception -- specifically whether linguistic knowledge is applied separately from general hearing or simultaneously with it. Several of the studies concern sound patterns in other languages and the role of a listener's linguistic experience, and will therefore be carried out at universities in France, Germany and the U.K. This project will help to establish new international partnerships for speech perception research comparing different language backgrounds. In addition, undergraduate students will be trained in the methods of speech perception research.

Understanding whether and how Earth system processes impacted human evolution is a challenge that generates broad interest among scientists and the general public. A recent NRC report noted how understanding of the environmental dynamics underpinning human evolution is ripe for major advances. This grant brings together scientists with a breadth of expertise, and this team will expand the paleoenvironmental data set upon which hypotheses about the relationship between environment and human origins must be based. The team will recover cores from long drill cores from five carefully selected ancient lake beds in Ethiopia and Kenya. These sites cover several important intervals of the late Neogene and Quaternary, close to key paleoanthropological sites, that will provide important new environmental information about the locales inhabited by ancient hominins. Funding requested here will support operational costs related to drilling and the initial core descriptions.

The goal of this project is to produce high-quality paleoenvironmental data from deposits close to key anthropological sites. Drilling allows the collection of unaltered samples from the same beds producing the hominin fossils, These near-pristine samples contain geochemical proxy data that can be used to decipher the region's environmental history. The team will correlate these drill cores to nearby marine records and to nearby outcrop records containing hominin and other vertebrate fossils, and to artifact assemblages by using tephras, paleomagnetism and other direct dating techniques. Drill cores from distal ancient lake beds avoid outcrop sample problems such as weathering, lacunae, and discontinuous expression of paleoenvironmental variables, while allowing examination of seasonal-scale environmental variability in varved intervals. The project will collect ~2400m of cores from nine bore holes at the North Awash and Chew Bahir Basins in Ethiopia, and the West Turkana, Baringo and Magadi Basins in Kenya. These areas have yielded some of the most important fossil hominin and artifact sites in the world, directly stimulating much of the current debate about human evolution and environmental dynamics. All sites contain long, continuous climate records spanning much of the last 4 million years, and are areas which are demonstrably sensitive to a range of environmental forcing mechanisms. The cores will be ideal for generating quantitative paleotemperature, paleoprecipitation, and other environmental reconstructions critical for understanding the environmental dynamics that early hominins experienced. These data will also provide a strong empirical base for evaluating both large and mesoscale models of African paleoclimate, and models linking climate, orography, hydrology and vegetation resources critical for early hominin survival.

The project includes training opportunities for nine American and African students, including focused outreach efforts to attract U.S. under-represented minority undergraduates through the University of Arizona's Saguaro Program. Many Kenyan and Ethiopian scientists are centrally involved in the project, and training and research opportunities will exist for more junior African scientists at all stages of the project. Public outreach activities will be carried out through three museum partners in the US and Africa. In the past, the local communities have benefited from scientific drilling activities by casing the boreholes so that they can be used as water wells.

Core samples and data collected by this project will be available to the general scientific community through the National Lacustrine Core Laboratory, ICDP NGDC, and the Smithsonian's Human Origins Database. The drilling operations will be co-funded by the International Continental Drilling Programme.

In the distant past, our ancestors experienced highly variable environmental and climatic conditions. During the Middle Stone Age, a period extending from 250,000 to 30,000 years ago, early humans experienced a series of wet/dry cycles in Africa related to ice age climates in more temperate parts of the world. Although theories of modern human origins and the evolution of human-like culture and behavior are generally based in the Middle Stone Age of Africa, our understanding of what makes the Middle Stone Age so important for these modern human features is limited.

One avenue of research is to investigate the nature of these cycles of glaciation in equatorial and southern African habitats where the earliest evidence for evolution of our species exists. In this project, conducted by Emory University doctoral student Joshua Robinson, under the mentorship of Dr. John Kingston, a series of established Middle Stone Age sites in Kenya, Ethiopia, Zambia, and the Democratic Republic of Congo will be utilized to study the local manifestations of global and regional environmental and climatic events. Through chemical analyses of the teeth of fossil animals from these archaeological sites, the research will reconstruct dietary patterns and climatic conditions. Specifically, carbon and oxygen isotopic analyses will form the basis for reconstructing vegetation, humidity, and rainfall at eight sample sites. These analyses will directly test the hypothesis that regional records fail to document local conditions that might be associated with these evolutionary innovations.

The ultimate goal of the research is to improve our understanding of the development of distinctly modern human behaviors, and the relationship between behavior and climate. This relationship is one of the enduring questions in anthropology, and the data to be collected here will provide new insights into when modern behavior emerged and delineate possible reasons for this emergence. The high-resolution, long-term database of environmental and climatic data generated by the study also will find broader application as an innovative framework for contextualizing and understanding modern climate change.

The possibility that human evolution in Africa has been strongly influenced by Earth's climatic and environmental history over the last several million years has been an important question at the forefront of paleoanthropological research. One fundamental question is: can any of the potential envionmental drivers of evolutionary change be reconstructed with enough precision to allow us to relate them with confidence to the episodes of speciation, extinction and cultural evolution known to anthropologists, and thereby test their relationships in time and space?

This team of paleoanthropologists and earth scientists plans to analyze climate and other environmental histories to provide direct tests of key hypotheses linking environmental history and mammal (including early human) evolution by collecting and analyzing detailed paleoenvironmental data at three key anthropological sites in Africa. They will collect continuous paleoenvironmental records by drilling long sediment cores from ancient lake beds in the northern Afar, Ethiopia (~3.8-2.9 million years ago-Ma), the Baringo Basin, Kenya (~3.2-2.35 Ma), and the Turkana Basin, Kenya (~2.3-1.42 Ma), and relate these records to the outcrops in the same basins that contain early human and other mammal fossils, as well as stone tools in the younger time periods. As a group these basins contain some of the most critical evidence for human evolutionary history in Africa. Although past investigators have reconstructed climate and other environmental histories from the outcrops in which the fossil humans and artifacts have been found, such environmental records are highly discontinuous due to the nature of the sediments where the fossils occur, and are unsuitable for many of the most informative geochemical records available today because of the weathering that has affected outcropping sediments. Drilling lakebeds near the fossil sites gets around these problems, because lake sediments accumulate much more continuously, and because drilling into the subsurface allows unweathered samples to be collected Funding for the drilling costs for this project has been secured from other sources: with the IPG funds the team will analyze the cores to generate quantitative and high resolution records of changes in temperature, precipitation, vegetation, fire and volcanic activity and other factors which may have influenced human evolution.

The primary research goal is to obtain long cores from these basins, each of which span critical intervals in human evolution and are close to hominin fossil and archaeological sites. The researchers will apply state-of-the-art paleoenvironmental and paleoclimate methods to these cores to assemble high resolution records covering much of the past four million years of East African environmental history. The team will then evaluate existing hypotheses and generate new hypotheses linking climate history to early human physical and cultural evolutionary adaptations. The paleoenvironmental and paleoecological data collected from the drill cores will be linked directly in time and space to the nearby fossil human, mammal and stone tool records by way of the numerous volcanic ashes present in both the cores and outcrops, along with other dating techniques. By comparing the new records to similar records from nearby ocean sediment cores the researchers plan be able to distinguish local from global drivers of environmental change and in the process test a series of hypotheses linking key events in human evolution with climate and other aspects of environmental history. Finally, the team will use these new, combined paleoenvironmental and paleoanthropological data sets, combined with novel modeling techniques to better understand how landscape and climate change across various scales of time and space may have affected the availability and predictability of critical ecosystem resources upon which early humans would have depended.

This project will greatly expand our understanding of African climate history and will be an opportunity to invigorate interest in human evolution and its relationship to climate with the US and African public. The project will train many American and African students during its field, analytical and internship/synthesis phases, and will generate numerous informal science learning opportunities through our collaborations with the National Museums of Kenya and Ethiopia and the Smithsonian Institution.

This project will collect and analyze lake sediment drill core records from key localities in Kenya and Ethiopia to vastly improve our understanding of the paleoenvironmental and paleoclimatic context of human evolution. Understanding the relationship between climate/environmental history and human evolution is an enduring challenge of broad scientific and public interest. Key questions include: How did climate and tectonic change interact during critical intervals of human evolution? What processes regulated this history on local to regional scales? Do local records of climate change reflect global changes? How and when did climatic and tectonic processes combine to influence early human habitats, resources, and demography? Were these changing conditions related to evolutionary processes and events in the human lineage? Research on this relationship cuts across Earth, environmental and anthropological sciences. The sediment drill cores we will collect from lake deposits will provide detailed and highly resolved records of environmental history. Through data collection and modeling we aim to fundamentally transform the debate concerning how environmental dynamics at global, regional and local scales may have shaped human evolutionary history.

The project will obtain continuous paleoenvironmental records by drilling long cores from five high-priority areas in Ethiopia (N. Awash River and Chew Bahir areas) and Kenya (W. Turkana, Tugen Hills and southern Kenya Rift/Lake Magadi) where highly-resolved, continuous lacustrine paleoclimate records can be collected through important time intervals in the same basins that contain fossils and artifacts. Rather than assume a linkage between environmental history and evolution, we designed this study as a series of data collection and modeling exercises to explicitly test overarching and local hypotheses about environmental and evolutionary dynamics. Our high-resolution (centennial-millennial scale) and datable geochemical, paleoecological and sedimentological records will allow quantitative reconstruction of paleoprecipitation, paleotemperature, paleohydrology and geomorphic evolution at a regional scale. We will correlate these records using high-resolution tephrostratigraphy, magnetostratigraphy and other geochronological techniques to adjacent exposures that contain hominin and other vertebrate fossils, and artifacts, as well as to nearby marine records. We will develop predictive numerical models of environmental change and ecosystem response during critical intervals of human evolution and evaluate these models against our new, high-resolution records. These experiments will examine how landscape and climate change across a hierarchy of temporal and spatial scales impacts the durability and predictability of critical ecosystem resources. They will allow us to evaluate the importance of climatic thresholds and abrupt environmental changes and better understand the earth system dynamics that might have shaped the record of human evolution. Our modeling will generate new, testable hypotheses of human evolution/Earth system dynamics, including possible feedbacks from evolving hominin populations to their environments. Our project will create a key data set for addressing fundamental, existential questions for humanity. We will provide training and internship opportunities for 16 American graduate students, 2 post-docs and 10 undergraduates, and numerous training opportunities for African student and professional participants during the field and initial core description phase of the project. We have also planned significant investment in informal education, through a 3-D video project and outreach activities we will coordinate with our three museum partners (Smithsonian Institution, National Museums of Kenya and Ethiopia), both during and following the drilling phase.

The goal of this research is to search for new fossil localities in eastern Uganda to understand the evolutionary processes associated with the origin of hominoids, the group of primates that includes apes and humans. The few known fossil sites in this area have yielded ancient animal and plant communities that include fossils of the oldest known apes. One of these apes,"Morotopithecus," shows evidence of using an upright trunk, the earliest known precursor of bipedalism in humans. Fossil data relevant to human origins is rare and evidence of such evolutionary specializations in apes provides critical insights into our evolution in Africa. Eastern Uganda represents one of the few known areas in the world where evidence has been found and further discoveries are essential.

Although the general locations of known fossil sites were established over 50 years ago, there have been no systematic attempts to explore this area for fossil localities. This has been due to the remote nature of this region, rugged terrain, large areas to reconnoiter (over 500 km2), heavy vegetation during all but the two-month dry season, limited geologic maps, and political instability related to armed livestock raiding. A recent national disarmament campaign has led to improved safety as well as the establishment of new settlements and access roads. Using newly available high-resolution satellite imagery, an extensive survey will be conducted (during the critical dry season) for fossiliferous sediments for the first time, possibly resulting in new sites and new fossils.

The broader impacts of this project include fostering of the career of women paleontologists, who are under-represented in field projects, as well as fostering the careers of African scholars in the form of collaborators and students. Researchers will disseminate their science widely through timely publication, teaching, the training of museum staff and public lectures.

An important dimension of language is the sound system and patterns of a given language. In fact, languages like English and Spanish include only a subset of the possible sounds of consonants, vowels, and the different ways they can combine. A greater understanding of what humans can produce and perceive in terms of sounds (phonetics) and how these sounds are organized and patterned (phonology) relies on investigation, documentation, and analysis of languages with different sounds and patterns than English and Spanish. This project will enable a conference to increase scientific understanding of how humans produce, perceive, and organize the phonetics and phonology of these diverse languages, focusing on a geographic region well-known for both its diversity and the urgent need to document this linguistic diversity in the face of language endangerment.


The goal of this project is to bring together indigenous and non-indigenous experts who study the linguistic diversity of the languages of Mexico and Central America. This workshop, the third iteration of "Sound Systems of Mexico and Central America (SSMCA 3)" will be held in October, 2018 at the University of Massachusetts, Amherst. Speakers will present scientific findings of the under-described and under-analyzed sound systems of the diverse languages of this part of the world. Besides plenary presentations from invited speakers, contributed presentations, and posters, the conference will include two roundtables. The first roundtable is devoted to discussing effective means of fostering collaboration between indigenous and non-indigenous scholars. The language sciences have seen tremendous intellectual advancement with the training of speakers of indigenous languages as linguists; this will seek to continue that advancement with a focus on phonetics and phonology. The second roundtable is focused on a broader impact of many language documentation projects, and will present effective means of translating language documentation into pedagogical materials that can be used in the schools to develop and promote literacy in indigenous languages and to maintain their use in indigenous communities. Additionally, SSMCA 3 will have four broader impacts: (1) promoting scholarly interaction and collaboration between indigenous and non-indigenous linguists in the task of documenting indigenous languages, (2) advancing the documentation of the un-described and under-described languages of Mexico and Central America, (3) publicizing the value of maintaining the indigenous languages of Mexico and Central America and the necessity of incorporating their use into public education, and (4) providing open access to all the presentations and materials from the conference online to any interested person.

Every time someone speaks, they produce complex sound waves. Understanding the acoustic details of these sound waves can help improve voice recognition technologies and provide insight on language differences which can potentially aid in language learning. A large body of work in linguistics and related disciplines has shown that speakers do not always pronounce sounds in the same way. For example, the sound "p" in English will be pronounced differently in different contexts (beginning of a word vs. end of word) and at different times simply because talkers are humans. People do not usually hear these differences, but they are present in the acoustics and can be measured. Variation in speech is natural and happens in every language. However, less is known about exactly how much variation occurs in different languages. This research seeks to address this gap by investigating whether speakers of some languages have more variable pronunciation than speakers of other languages and what might explain the difference.

One frequently assumed hypothesis says that speakers of languages with more sounds will show less variation (be more precise) when they pronounce those sounds. The researchers will gather data from different languages to test and revise this hypothesis. They will also develop concrete methods for measuring acoustic variability in language which can then be applied to future work. The experiments compare stop sounds in Hindi ("b", "bh", "p" and "ph") and English ("b" and "p"), and sibilant sounds in Polish ("s", "ś", and "sz") and French ("s" and "sh"). Both experiments examine multiple acoustic cues to the contrasts in each language. The second portion of the project will use the conclusions from these experiments to investigate whether speakers imitate the variability of other speakers that they hear. It is well documented that speakers change their pronunciation based on speech they have recently heard, but it is not known whether speakers will change the amount of variability in their speech based on what they have heard. To address this question, the researchers will carry out an imitation study where speakers listen to speech before being prompted to speak to see if the variability in their speech changes after listening. The results of these studies will increase understanding of variability in pronunciation across different languages and contexts.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).

Humans have a unique suite of biological adaptations, many of which can be observed at various points in the primate and human evolutionary fossil record. To investigate how and why these adaptations occurred, it is critical that scientists consider not only the fossils themselves but their ecological and environmental contexts. This doctoral dissertation project addresses important questions about the optimal time scale(s) for investigating links between early humans and their environments. The investigators use data from high-resolution geological sediments to reconstruct and analyze environmental change at various scales of observation and consider how different patterns emerge depending on scale. The project also includes opportunities for student training and mentoring, public science outreach activities, and strengthening of international research collaborations.

Interpretations of large- and small-scale paleoecological trends are developed to assess how scale may influence interpretations of mammalian dietary ecology, as well as early human environments within a relatively continuous geologic sequence where fossil apes and humans have been recovered. The investigators develop long-term, coarsely resolved dietary data for 8 herbivore lineages for periods from 13-8.5 Ma and 5.3-1.6 Ma. They develop temporally refined, short-term dietary data for herbivores from 4-2 Ma. Each fossil sample is correlated to a specific geologic horizon— and subsequently a specific date—for which detailed paleoclimatic and paleobotanical data have been published. The project enables the diets of individual animals to be reconstructed to the level of vegetation type and then be compared to outstanding paleoclimatic datasets in order to better understand prevailing modes of paleoecological change in the region. These data can advance the integration of paleoecological patterns at various temporal scales to help clarify the types of environmentally-selective forces experienced by the hominin and hominoid lineages.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.