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The University of Maine

2009

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Full-Text Articles in Life Sciences

Investing In Maine Research Infrastructure: Sustainable Forest Bioproducts, Michael Eckardt, Stephen Shaler, Hemant P. Pendse, Adriaan R. P. Van Heiningen, Robert G. Wagner Dec 2009

Investing In Maine Research Infrastructure: Sustainable Forest Bioproducts, Michael Eckardt, Stephen Shaler, Hemant P. Pendse, Adriaan R. P. Van Heiningen, Robert G. Wagner

University of Maine Office of Research Administration: Grant Reports

The University of Maine, the University of Southern Maine, several baccalaureate institutions in the state, along with other federal, state and local public, private, and non-profit institutions will collaborate to create the Forest Bioproducts Research Institute (FBRI) at the University of Maine. The vision of the FBRI is to advance understanding about the scientific underpinnings, system behavior, and policy implications for the production of forest-based bioproducts that meet societal needs for materials, chemicals, and fuels in an economically and ecologically sustainable manner.

The research plans Integrate three themes. They are (1) forest sustainability modeling of life cycle assessment, (2) integrated …


Minerva 2009, The Honors College Dec 2009

Minerva 2009, The Honors College

Minerva

This issue of Minerva includes a story on alumna Betsy Leitch and her husband Bill Leitch, Betsy's connection to Colvin Hall, and their ongoing support of Honors; an article about Colvin Hall renovations and the opening of the Margaret Chase Smith Visiting Faculty Suite; and an interview with Pulitzer Prize-winning Honors graduate, Bettina Boxall. Other highlights include the story of Honors graduate Adam Jones and his involvement in saving the USS Alabama.


Salinity And Stratification In The Gulf Of Maine: 2001-2008, Heather E. Deese-Riordan Dec 2009

Salinity And Stratification In The Gulf Of Maine: 2001-2008, Heather E. Deese-Riordan

Electronic Theses and Dissertations

The salinity and vertical density structure (stratification) of the Gulf of Maine strongly influence the physical and biological character of the region including: circulation and transport, vertical mixing, and primary productivity. Variability in salinity and stratification also provides insights into the character and timing of the oceanic waters entering the region, a key to predicting regional climate change. This thesis addresses outstanding questions related to variability in salinity and the relative role of salinity and temperature in creating stratification. Hourly observations from Ocean Observing System buoys throughout the Gulf provide the primary data source for this investigation. Analysis of estimated …


Investigating Saxitoxin Resistance In Softshell Clams (Mya Arenaria): Patterns Of Inheritance And Improvements On Methodology For Tracking And Identification, Scott A. Hamilton Dec 2009

Investigating Saxitoxin Resistance In Softshell Clams (Mya Arenaria): Patterns Of Inheritance And Improvements On Methodology For Tracking And Identification, Scott A. Hamilton

Electronic Theses and Dissertations

Attempts to characterize and study the population dynamics of the softshell clam Mya arenaria in relation to a mutation which confers resistance to paralytic shellfish toxins are complicated by a lack of non-lethal genotyping techniques, reliable tagging methods and an understanding of the inheritance patterns of the marker. Presented here, is a straightforward and non-lethal technique for clam genotyping, a new method for the long term tagging of clams, and the offspring genotype frequencies from a number of pair matings between clams of known genotype. Hemolymph extracted from M. arenaria was used directly in a polymerase chain reaction (PCR) to …


Light-Related Photosynthetic Gene Expression And Enzyme Activity In The Heterokont Alga Vaucheria Litorea And Its Symbiotic Partner The Sacoglossan Mollusc Elysia Chlorotica, Kara M. Soule Dec 2009

Light-Related Photosynthetic Gene Expression And Enzyme Activity In The Heterokont Alga Vaucheria Litorea And Its Symbiotic Partner The Sacoglossan Mollusc Elysia Chlorotica, Kara M. Soule

Electronic Theses and Dissertations

Photosynthesis is comprised of tightly coupled reactions and therefore requires strict matrices of regulation, particularly involving alterations in gene expression and enzyme activity within the nucleus and plastid. Extensive research has been carried out on these light-regulated mechanisms in plants and green algae, however, much less is known in the red algal lineage, including heterokonts. The goal of this study was to investigate the influence of light on photosynthetic gene expression and select enzyme activity in the heterokont alga Vaucheria litorea and its symbiotic partner Elysia chlorotica, a photosynthetic sacoglossan mollusc (sea slug). Elysia chlorotica harbors V. litorea plastids …


Collaborative Research: Differential Expression Of Oxygen-Binding Proteins In Antarctic Fishes Affects Nitric Oxide-Mediated Pathways Of Angiogenesis And Mitochondrial Biogenesis, Bruce Sidell Nov 2009

Collaborative Research: Differential Expression Of Oxygen-Binding Proteins In Antarctic Fishes Affects Nitric Oxide-Mediated Pathways Of Angiogenesis And Mitochondrial Biogenesis, Bruce Sidell

University of Maine Office of Research Administration: Grant Reports

The polar ocean presently surrounding Antarctica is the coldest, most thermally stable marine environment on earth. Because oxygen solubility in seawater is inversely proportional to temperature, the cold Antarctic seas are an exceptionally oxygen-rich aquatic habitat. Eight families of a single perciform suborder, the Notothenioidei, dominate the present fish fauna surrounding Antarctica. Notothenioids account for approximately 35% of fish species and 90% of fish biomass south of the Antarctic Polar Front. Radiation of closely related notothenioid species thus has occurred rapidly and under a very unusual set of conditions: relative oceanographic isolation from other faunas due to circumpolar currents and …


Explore It! Building The Next Generation Of Sustainable Energy Researchers, Darrell W. Donahue, David J. Neivandt Nov 2009

Explore It! Building The Next Generation Of Sustainable Energy Researchers, Darrell W. Donahue, David J. Neivandt

University of Maine Office of Research Administration: Grant Reports

This award will establish an REU Site at the University of Maine. The program will engage 10 undergraduates each year for three years in a 10-week summer research experience. This REU site will leverage a focus area represented by the newly established University of Maine Forest Bio-products Research Institute (FBRI). Undergraduate students will conduct research advancing their knowledge of sustainable forest bio-products and will gain a detailed understanding of one of the thematic elements of the research effort as well as a broad understanding of all areas, specifically: 1) sustainable and life cycle analysis; 2) solids extraction/modification; 3) process control …


What Is The Downeast Fisheries Heritage Trail?, Maine Sea Grant Nov 2009

What Is The Downeast Fisheries Heritage Trail?, Maine Sea Grant

Downeast Fisheries Trail

The Downeast Fisheries Trail is an educational trail that showcases active and historic fisheries heritage sites, such as fish hatcheries, aquaculture facilities, fishing harbors, clam flats, processing plants and other related public places in an effort to educate residents and visitors about the importance of the region’s maritime heritage and the role of marine resources to the area’s economy.


Career: Physiological Genetics Of The Dwarf Surf Clam, Mulinia Lateralis, Paul D. Rawson Oct 2009

Career: Physiological Genetics Of The Dwarf Surf Clam, Mulinia Lateralis, Paul D. Rawson

University of Maine Office of Research Administration: Grant Reports

Heterosis, or hybrid vigor, is a condition where more heterozygous individuals physiologically outperform more homozygous individuals. Although heterosis has often been reported for marine bivalves, as well as other taxa, the physiological and genetic bases of heterosis are still poorly understood. The proposed research will use a combination of quantitative and molecular genetic approaches to examine the physiological and genetic underpinnings of heterosis in the dwarf surf clam, Mulinia lateralis. The specific goals of this work are:

1) to determine the genetic and physiological basis of growth rate variation,
2) to estimate the degree to which the physiological components …


Collaborative Research: The Response Of Lakes To Disturbance And Climate Change: Calibrating Sedimentary Records To Test The Landscape Position Concept, Jasmine E. Saros Oct 2009

Collaborative Research: The Response Of Lakes To Disturbance And Climate Change: Calibrating Sedimentary Records To Test The Landscape Position Concept, Jasmine E. Saros

University of Maine Office of Research Administration: Grant Reports

Landscape disturbance and climate change affect lakes in proportion to their contact with ground water, sometimes resulting in different responses in neighboring lakes. This project develops methods for reconstructing past water chemistry and food webs of lakes. The biological and chemical deposits in surface sediment samples will be compared with the water in 62 modern lakes. The resulting relationships will be tested by comparing sediment cores with 24 years of observations from the North Temperate Lakes Long Term Ecological Research (NTL-LTER) site. The methods will then be used to reconstruct 150 years of history for several lakes, adding perspective to …


Tb203: Recent Advances In The Biology And Genetics Of Lowbush Blueberry, Daniel J. Bell, Lisa J. Rowland, John Smagula, Frank Drummond Oct 2009

Tb203: Recent Advances In The Biology And Genetics Of Lowbush Blueberry, Daniel J. Bell, Lisa J. Rowland, John Smagula, Frank Drummond

Technical Bulletins

For lowbush blueberries, this publication presents an in-depth look at the biology and genetics of lowbush blueberry. The authors provide details on its genetic composition and the outline the usefulness of various biochemical, genomic, and other markers in studying the plants genetic structure. The authors also provide an overview of the plant’s economic value to Maine, nutritional value, and its life history.


The Lobster Bulletin, Fall 2009, Lobster Institute, University Of Maine Oct 2009

The Lobster Bulletin, Fall 2009, Lobster Institute, University Of Maine

Lobster Bulletin

The Lobster Bulletin newsletter includes research updates, and information on lobsters and the lobster industry. The Lobster Institute at the University of Maine is dedicated to protecting and conserving the lobster resource, and enhancing lobstering as an industry and a way of life.

Headlines in the Fall 2009 issue include:

  • Lobster Council of Canada Has Great Potential
  • Lobster Institute Events of Interest
  • 2010 Canadian/U.S. Lobstermen's Town Meeting
  • Research Report: Lobster Health Coalition Makes Progress on Baseline Health Data
  • Research Report: LFA 33/34 Lobster Moult Timing & Quality Monitoring Project Update
  • Fisheries On-Line Forum Launched


The Dandy Scroll, Fall 2009, University Of Maine Pulp And Paper Foundation Oct 2009

The Dandy Scroll, Fall 2009, University Of Maine Pulp And Paper Foundation

General University of Maine Publications

The Fall 2009 issue of The Dandy Scroll newsletter produced by the University of Maine Pulp and Paper Foundation.


Collaborative Research: Abandoned Elephant Seal Colonies In Antarctica: Integration Of Genetic, Isotopic, And Geologic Approaches Toward Understanding Holocene Environmental Change, Brenda L. Hall Sep 2009

Collaborative Research: Abandoned Elephant Seal Colonies In Antarctica: Integration Of Genetic, Isotopic, And Geologic Approaches Toward Understanding Holocene Environmental Change, Brenda L. Hall

University of Maine Office of Research Administration: Grant Reports

During previous NSF-sponsored research, the PI's discovered that southern elephant seal colonies once existed along the Victoria Land coast (VLC) of Antarctica, a region where they are no longer observed. Molted seal skin and hair occur along 300 km of coastline, more than 1000 km from any extant colony. The last record of a seal at a former colony site is at ~A.D. 1600. Because abandonment occurred prior to subantarctic sealing, disappearance of the VLC colony probably was due to environmental factors, possibly cooling and encroachment of land-fast, perennial sea ice that made access to haul-out sites difficult. The record …


Tb202: Composition And Biomass Of Forest Floor Vegetation In Experimentally Acidified Paired Watersheds At The Bear Brook Watershed In Maine, Peter Kenlan, G. B. Wiersma, A. S. White, I. J. Fernandez Sep 2009

Tb202: Composition And Biomass Of Forest Floor Vegetation In Experimentally Acidified Paired Watersheds At The Bear Brook Watershed In Maine, Peter Kenlan, G. B. Wiersma, A. S. White, I. J. Fernandez

Technical Bulletins

The percentage cover (abundance), frequency of occurrence, biomass, species richness, and species diversity of understory herbs was measured on a paired watershed ecosystem in eastern Maine, USA. This paired watershed site (Bear Brook Watershed in Maine, BBWM) has had the West Bear Brook Watershed treated bi-monthly with granular ammonium sulfate at a rate of 28.8 kg S ha-1 yr-1 and 25.2 kg N ha-1 yr-1 since 1989. East Bear Brook Watershed serves as the reference site. More than 100 plots were randomly located across the two watersheds. The data suggest that there is generally a lower frequency of occurrence of …


Community College Student Participation In Undergraduate Research: An Explanatory Case Study For Faculty And Research Mentors, Dana L. Peterson Aug 2009

Community College Student Participation In Undergraduate Research: An Explanatory Case Study For Faculty And Research Mentors, Dana L. Peterson

Electronic Theses and Dissertations

This study adapted the current model of science undergraduate research experiences (URE's) and applied this novel modification to include community college students. Numerous researchers have examined the efficacy of URE's in improving undergraduate retention and graduation rates, as well as matriculation rates for graduate programs. However, none have detailed the experience for community college students, and few have employed qualitative methodologies to gather relevant descriptive data from URE participants. This study included perspectives elicited from both non-traditional student participants and the established laboratory community. The purpose of this study was to determine the effectiveness of the traditional model for a …


Influence Of Silvicultural Treatment, Site Characteristics, And Land Use History On Native And Nonnative Forest Understory Plant Composition On The Penobscot Experimental Forest In Maine, Elizabeth Bryce Aug 2009

Influence Of Silvicultural Treatment, Site Characteristics, And Land Use History On Native And Nonnative Forest Understory Plant Composition On The Penobscot Experimental Forest In Maine, Elizabeth Bryce

Electronic Theses and Dissertations

This study investigates forest understory plant diversity and composition in managed and unmanaged stands within the context of a long-term silvicultural experiment in the Acadian Forest of Maine. I examined the effects of silvicultural intensity and past land use on understory plant species diversity and composition. Silvicultural treatments include three variants of the selection system, three variants of the shelterwood system, modified and fixed diameter-limit cutting, and an unregulated harvest. Two types of unmanaged stands were studied: a continuously forested natural area and secondary forest stands on old fields. Chapter 1 presents analysis of understory plant diversity and composition in …


Thresholds And The Mismatch Between Environmental Laws And Ecosystems, Malcolm L. Hunter Jr., Michael J. Bean, David Lindenmayer, David S. Wilcove Jul 2009

Thresholds And The Mismatch Between Environmental Laws And Ecosystems, Malcolm L. Hunter Jr., Michael J. Bean, David Lindenmayer, David S. Wilcove

Publications

No abstract provided.


The Lobster Bulletin, Summer 2009, Lobster Institute, University Of Maine Jul 2009

The Lobster Bulletin, Summer 2009, Lobster Institute, University Of Maine

Lobster Bulletin

The Lobster Bulletin newsletter includes research updates, and information on lobsters and the lobster industry. The Lobster Institute at the University of Maine is dedicated to protecting and conserving the lobster resource, and enhancing lobstering as an industry and a way of life.

Headlines in the Summer 2009 issue include:

  • Development of Best Management Practices to Reduce or Eliminate Stress on Lobsters
  • Mariner Beverages, USA Wine West Unveil New Wine to Benefit the Lobster Institute
  • Lobster Institute Presents First Rising Star Award to Lobster Gram, Inc.
  • Best Management Practices to Reduce or Eliminate Stress from Hauling & Handling of Lobsters …


Adaptive Changes In Life History And Survival Following A New Guppy Introduction, Swanne P. Gordon, David N. Reznick, Michael T. Kinnison, Michael J. Bryant, Dylan J. Weese, Katja Rasanen, Nathan P. Millar, Andrew P. Hendry Jul 2009

Adaptive Changes In Life History And Survival Following A New Guppy Introduction, Swanne P. Gordon, David N. Reznick, Michael T. Kinnison, Michael J. Bryant, Dylan J. Weese, Katja Rasanen, Nathan P. Millar, Andrew P. Hendry

Biology and Ecology Faculty Scholarship

Numerous studies of wild populations have shown that phenotypic traits can change adaptively on short timescales, but very few studies have considered coincident changes in major fitness components. We here examine adaptive changes in life-history traits and survival rates for wild guppies introduced into new environments. Female life-history traits in the derived (Damier River) populations diverged from the ancestral (Yarra River) population, as a result of adaptation to predation regime (high vs. low) and other aspects of the local river. Moreover, some components of the derived Damier populations, particularly juveniles, now show higher survival in the Damier than do contemporary …


American Lobster Settlement Index: Looking Back, Looking Ahead 1989-2009, Maine Sea Grant Jun 2009

American Lobster Settlement Index: Looking Back, Looking Ahead 1989-2009, Maine Sea Grant

Maine Sea Grant Publications

Hosted by Bigelow Laboratory for Ocean Sciences and Maine Department of Marine Resources, a workshop celebrating the 20th anniversary of the American Lobster Settlement Index convened some 40 scientists, managers, and industry members and guests from New England and Atlantic Canada who have been involved in the monitoring and research linked to the Index over the years. The workshop's aim was to look back at the accomplishments of the Settlement Index over the past two decades and to set future monitoring, research and outreach priorities for the program. Rick Wahle of Bigelow Laboratory and Carl Wilson of DMR coordinated the …


Tb201: Comparison Of The Efficacy Of Sodium Acid Sulfate And Citric Acid Treatments In Reducing Acrylamide Formation In French Fries, Byungchul Kim, L. Brian Perkins, Beth Calder, Lawrence A. Leblanc Jun 2009

Tb201: Comparison Of The Efficacy Of Sodium Acid Sulfate And Citric Acid Treatments In Reducing Acrylamide Formation In French Fries, Byungchul Kim, L. Brian Perkins, Beth Calder, Lawrence A. Leblanc

Technical Bulletins

Two acidulant food additives, sodium acid sulfate (SAS) and citric acid, were investigated for their effectiveness in reducing acrylamide formation in french fries. Acrylamide concentration was determined by gas chromatography-mass spectrometry (GC-MS) after cleanup of french fry extracts by passage through a C-18 column and derivitization by bromination. At a frying temperature of 180°C, both acidulants appeared ineffective, possibly due to the rapid rate of acrylamide formation, which surpassed the capacity of the acidulants to protonate acrylamide intermediates. At the lowest frying temperature tested (160°C), 3% SAS and 3% citric acid significantly (P < 0.05) inhibited acrylamide formation as compared to the control. However, 3% SAS appeared to inhibit acrylamide formation more effectively than citric acid at 160°C, as well as at frying temperatures of 170 and 180°C. Our results indicate that acrylamide formation during frying can be reduced by treatment of potatoes with 3% SAS or citric acid, but SAS, a stronger acid with a lower pKa, is the more effective acidulant.


Us Globec Nwa/Georges Bank: Processes Controlling Abundance Of Dominant Copepods On Georges Bank: Local Dynamics And Large-Scale Forcing, David W. Townsend Jun 2009

Us Globec Nwa/Georges Bank: Processes Controlling Abundance Of Dominant Copepods On Georges Bank: Local Dynamics And Large-Scale Forcing, David W. Townsend

University of Maine Office of Research Administration: Grant Reports

A fundamental goal of Biological Oceanography is to understand how underlying biological-physical interactions determine abundance of marine organisms. For animal populations, it is well known that factors controlling survival during early life stages (i.e., recruitment) are strong determinants of adult population size, but understanding these processes has been difficult due to model and data limitations. Recent advances in numerical modeling, together with new 3D data sets, provide a unique opportunity to study the biological-physical processes controlling zooplankton population size. This project uses an existing state-of-the-art biological/physical numerical model (FVCOM) together with the recently processed large 3D data set from the …


Acetylcholine-Induced Membrane-Potential Oscillations In Xenopus Laevis Oocytes, Corrine N. Grant May 2009

Acetylcholine-Induced Membrane-Potential Oscillations In Xenopus Laevis Oocytes, Corrine N. Grant

Honors College

Over the past several years, amphibian species have shown a sharp decline in population numbers. Many factors are believed to play a role in the loss of amphibian species. One of particular interest is the increase in ultraviolet (UV) radiation reaching Earth’s surface. To estimate the health of a species, an assay needed to be developed. Health can be determined by measuring the ion channel functionality of the amphibian oocyte membrane. To develop this assay, we used acetylcholine to induce a membrane-potential oscillation in Xenopus laevis oocytes. Several studies have studied the membrane-potential oscillation of calcium-dependent chloride channels activated by …


Comparisons Of Native And Non-Native Lady Beetles: Habitat Distribution And Interactions With Prey And Competitors, Christy J. L. Finlayson May 2009

Comparisons Of Native And Non-Native Lady Beetles: Habitat Distribution And Interactions With Prey And Competitors, Christy J. L. Finlayson

Electronic Theses and Dissertations

Lady beetles (Coleoptera: Coccinellidae), as a group, are considered beneficial because they prey on plant pests. A number of studies suggest that non-native species introduced for biological control have replaced native species in agriculture. Agricultural and non-agricultural habitats were thus surveyed in Maine to determine if native species were still dominant in some areas. In 2004 and 2005, 3,487 and 2,903 beetles were collected, respectively, with non-native species dominant in all but one habitat (coniferous forest). Native species were found in very low numbers in all habitats surveyed. Comparisons between species were then conducted to determine if differences exist that …


The Chemistry Of Acidic Soils In Humid, Temperate Forested Watersheds With Emphasis On Phosphorus, Aluminum And Iron, Micheal Sanclements May 2009

The Chemistry Of Acidic Soils In Humid, Temperate Forested Watersheds With Emphasis On Phosphorus, Aluminum And Iron, Micheal Sanclements

Electronic Theses and Dissertations

Acidification of soils can result from natural processes (i.e. pedogenesis) and from atmospherically derived sulfur (S) and nitrogen (N) which originate from anthropogenic emissions. Research on the effects of acidification has typically focused on base cations, N and aluminum (Al). The Bear Brook Watershed in Maine (BBWM) (a long-term, whole-watershed acidification experiment) demonstrated increased episodic stream export of Al, iron (Fe), and phosphorus (P) in the treated watershed, suggesting that acidification can also affect P. This research evaluates (a) the physical and chemical distribution of P, (b) mechanisms controlling soil P accumulation, mobilization, and availability in humid, temperate forested ecosystems, …


Analysis Of Melamine And Cyanuric Acid By Liquid Chromatography With Diode Array Detection And Tandem Mass Spectrometry, Byungchul Kim May 2009

Analysis Of Melamine And Cyanuric Acid By Liquid Chromatography With Diode Array Detection And Tandem Mass Spectrometry, Byungchul Kim

Electronic Theses and Dissertations

Melamine and cyanuric acid are the compounds that caused the global incidences of kidney related disease to pets and infants in North America and China during the last two years. After a concerted research effort by U.S. laboratories, it was discovered that they were intentionally added in raw ingredients to pet foods or milk to increase nitrogen levels without providing protein. Melamine and cyanuric acid can easily combine by hydrogen bonding and produce a melamine-cyanurate complex that directly caused renal failure to pets and infants who consumed the tainted pet food or milk. Many analytical methods for the determination of …


The Lobster Bulletin, Spring 2009, Lobster Institute, University Of Maine Apr 2009

The Lobster Bulletin, Spring 2009, Lobster Institute, University Of Maine

Lobster Bulletin

The Lobster Bulletin newsletter includes research updates, and information on lobsters and the lobster industry. The Lobster Institute at the University of Maine is dedicated to protecting and conserving the lobster resource, and enhancing lobstering as an industry and a way of life.

Headlines in the Spring 2009 issue include:

  • Canadian Officials May Consider Ban of Floating Rope
  • Sustainability Labeling & Traceability Trigger Much Discussion at Lobster Institute's 2009 Canadian/U.S. Lobstermen's Town Meeting
  • Research Report: FSRS Lobster Recruitment Index
  • Research Report: American Lobster Stock Assessment 2009
  • The Lobster Institute presents Lobster College 2009


Maine’S Climate Future – An Initial Assessment, University Of Maine Climate Change Institute Apr 2009

Maine’S Climate Future – An Initial Assessment, University Of Maine Climate Change Institute

General University of Maine Publications

This report considers past change over geologic time, recent evidence of accelerated rates of change, and the implications of continued climate change in Maine during the 21st century as a result of greenhouse gas emissions and their associated pollutants. Even if a coordinated response succeeds in eliminating excess greenhouse gas emissions by the end of the century, something that appears highly unlikely today, climate change will continue because the elevated levels of carbon dioxide (CO2) can persist in the atmosphere for thousands of years to come.


Criterial Noise Effects On Rule-Based Category Learning: The Impact Of Delayed Feedback, Shawn W. Ell, David A. Ing, Todd W. Maddox Mar 2009

Criterial Noise Effects On Rule-Based Category Learning: The Impact Of Delayed Feedback, Shawn W. Ell, David A. Ing, Todd W. Maddox

Psychology Faculty Scholarship

Variability in the representation of the decision criterion is assumed in many category learning models yet few studies have directly examined its impact. On each trial, criterial noise should result in drift in the criterion and will negatively impact categorization accuracy, particularly in rule-based categorization tasks where learning depends upon the maintenance and manipulation of decision criteria. The results of three experiments test this hypothesis and examine the impact of working memory on slowing the drift rate. Experiment 1 examined the effect of drift by inserting a 5 s delay between the categorization response and the delivery of corrective feedback, …