Science Current Events | Science News | Brightsurf.com
 

The importance of (experimental) design

February 25, 2014
One of the hottest debates in evolutionary biology concerns the origin of behaviour: is it genetically encoded or do animals and birds copy their parents or other individuals? A classic experiment published in 2000 seemed to provide overwhelming evidence that a particular behavioural choice (whether individuals of a species of swallow breed in a small colony or a large one) is largely genetically determined. Together with colleagues in France, Richard Wagner of the University of Veterinary Medicine, Vienna has re-examined the data and shown that the findings could be explained by random choice. The design of the original experiment - which represents a blueprint for a vast range of studies of heritability of behaviour - contains two pitfalls that combine to undermine the conclusions. The results are published in the journal Scientific Reports.

There are clear advantages to living in cities: safety, ready availability of infrastructure, plenty of company etc. Nevertheless, a large number of people eschew them for the benefits of country life, such as clean air and lots of space. Many species of animals, and particularly birds, face the same choice between living in large groups or remaining in smaller ones, thereby avoiding disadvantages of larger colonies such as the increased risk of disease and increased aggression from neighbours. What causes different individuals of a particular species to take the decisions they do?

It's all in the genes

One possible explanation is that animals and birds might be genetically influenced to breed in smaller or larger colonies. This idea gained widespread acceptance in 2000, when Charles and Mary Brown reported the results of a field experiment of unprecedented scope. The Browns worked on Cliff Swallows, a species of American swallow that breeds in colonies of variable size. Some individuals appear to be more resistant to nest parasites so can breed in larger, more parasite-infested colonies where they can achieve higher foraging efficiencies by following their many neighbours to the insect swarms on which they feed. The scientists cross-fostered an astounding 2,000 nestlings from nests in small colonies to nests in large colonies and vice versa and recaptured over 700 of the birds when they returned to breed in the following years. Analysis of the data showed convincingly that swallows hatched in larger colonies (but reared in smaller ones) chose to breed in large colonies, whereas the reverse was true for swallows hatched in small colonies. In other words, the birds' choice is determined by genetic factors.

Or is it?

Appealing though the conclusion might be, something does not sound quite right. How would a genetic component of the choice of group size be selected and maintained throughout evolution? Étienne Danchin of the University of Toulouse and Richard Wagner of the Vetmeduni's Konrad Lorenz Institute of Ethology wondered whether the results might not be influenced too much by the experimental design. Together with Éric Wajnberg, a modelling specialist at the INRA in Sophia Antipolis, they simulated the data in the original paper and found that the results could be generated by chance.

The problem stems largely from the fallacy known as "regression to the mean" (RTM), which was first identified by Sir Francis Galton, a cousin of Charles Darwin, in the 19th century. It results from the fact that uncommonly large or small measurements are generally followed by more normal measurements simply because normal values are by definition far more common than extreme ones. In the Browns' experiment, when individuals are fostered from small to large colonies they will on average recruit to colonies that are statistically smaller than their foster colony because these are closer to the mean colony size and vice versa.

Danchin and Wagner actually found a second problem with the original data analysis. The so-called "spatial fallacy" was discovered by Arie van Noorwijk in 1984 and occurs when the set of potential dispersal sites differs among individuals according to where they were born. Together the two fallacies can account for the experiment's results, even in the absence of an inherited component of the selection of colony size.

A question of design

The latest calculations are important for two reasons. First, they call the original conclusions into question and should thus encourage researchers to reconsider the role of genetic factors in certain behavioural decisions. Secondly, they sound a clear warning to all those working in behavioural science. As Wagner says, "The biggest shock is that the very experimental design that is widely used to control for all extraneous effects actually creates the RTM fallacy. Even the most carefully designed studies can suffer from the problem, making their results invalid." Fortunately the scientists have proposed a way to avoid both pitfalls. Their simulations showed that restricting comparisons to individuals with the same set of options (in the present case by fostering all offspring to a single colony) can give rise to data that are immune to the pitfalls.

The Nature Publishing Group has just published the paper "Avoiding pitfalls in estimating heritability with the common options approach" by Étienne Danchin, Éric Wajnberg and Richard H. Wagner in its online journal Scientific Reports, where it is freely available. (Scientific Reports Volume 4, doi:10.1038/srep03974)

University of Veterinary Medicine Vienna


Related Experimental Design Current Events and Experimental Design News Articles


New release of Glioblastoma Atlas sheds light on deadly disease
Robust new data added to the Ivy Glioblastoma Atlas Project (Ivy GAP) changes the scope and impact of this publicly available resource for researchers and clinicians searching for treatments for this most deadly and aggressive of brain cancers, glioblastoma multiforme.

Consumption rises with automated bill payment
The adage "out of sight, out of mind" applies to electricity use, according to new research from Duke University's Sanford School of Public Policy.

Scientists unknowingly tweak experiments: ANU media release
A new study has found some scientists are unknowingly tweaking experiments and analysis methods to increase their chances of getting results that are easily published.

Gene networks for innate immunity linked to PTSD risk
Researchers at the Veterans Affairs San Diego Healthcare System and University of California, San Diego School of Medicine, with colleagues in New York and the United Kingdom, have identified genetic markers, derived from blood samples that are linked to post-traumatic stress disorder (PTSD).

To beet or not to beet? Researchers test theories of beet juice benefits
Athletes who down beet juice before exercising to increase blood flow and improve performance may be surprised at the results of a recent study conducted at Penn State's Noll Laboratory.

Sleeping after learning is important for infants' long-term memory
Sleep facilitates memory consolidation - not just in adults, but also in infants in their first year of life. This has been demonstrated by a team of researchers headed by Dr Sabine Seehagen at the Ruhr-Universität Bochum, for the first time using an experimental design that assesses declarative memories, i.e. memories for facts and events.

@RiceUNews 3-D maps reveal the genome's origami code
In a triumph for cell biology, researchers have assembled the first high-resolution, 3-D maps of entire folded genomes and found a structural basis for gene regulation -- a kind of "genomic origami" that allows the same genome to produce different types of cells. The research appears online today in Cell.

Space travel is a bit safer than expected
Analysis of data from the MATROSHKA experiment, the first comprehensive measurements of long-term exposure of astronauts to cosmic radiation, has now been completed.

Humans' big brains might be due in part to newly identified protein
A protein that may partly explain why human brains are larger than those of other animals has been identified by scientists from two stem-cell labs at UC San Francisco, in research published in the November 13, 2014 issue of Nature.

Entanglement made tangible
Quantum entanglement refers to the "pairing" of two subatomic particles in such a way that they form a whole quantum system.
More Experimental Design Current Events and Experimental Design News Articles

Experimental Design: Procedures for the Behavioral Sciences

Experimental Design: Procedures for the Behavioral Sciences
by Roger E. Kirk (Author)


Experimental Design: Procedures for Behavioral Sciences, Fourth Edition is a classic text with a reputuation for accessibility and readability. It has been revised and updated to make learning design concepts even easier. Roger E. Kirk shows how three simple experimental designs can be combined to form a variety of complex designs. He provides diagrams illustrating how subjects are assigned to treatments and treatment combinations. New terms are emphasized in boldface type, there are summaries of the advantages and disadvantages of each design, and real-life examples show how the designs are used.

Experimental Design for Biologists, Second Edition

Experimental Design for Biologists, Second Edition
by David J. Glass (Author)


The effective design and analysis of experiments in biology are critical to success, yet graduate students in biological and medical sciences typically receive very little formal training in these steps. With feedback from readers of the first edition, colleagues, and students taking the very popular experimental design courses taught by the author, this second edition of Experimental Design for Biologists retains the engaging writing style while organizing the book around the four elements of experimental design: the framework, the system, the experiment, and the model. The approach has been tested in the classroom, where the author has taught numerous graduate students, MD/PhD students, and postdoctoral fellows. The goal of every scientist is to discover something new and with the aid...

Statistics for Experimenters: An Introduction to Design, Data Analysis, and Model Building (Wiley Series in Probability and Statistics)

Statistics for Experimenters: An Introduction to Design, Data Analysis, and Model Building (Wiley Series in Probability and Statistics)
by George E. P. Box (Author), William G. Hunter (Author), J. Stuart Hunter (Author)


Introduces the philosophy of experimentation and the part that statistics play in experimentation. Emphasizes the need to develop a capability for ``statistical thinking'' by using examples drawn from actual case studies.

Experimental Design for the Life Sciences

Experimental Design for the Life Sciences
by Graeme Ruxton (Author), Nick Colegrave (Author)


At the core of good research lies the careful design of experiments. However, all too often a successful design comes only after a painful trial-and-error process that wastes valuable time and resources.

Now in a new edition, Experimental Design for the Life Sciences teaches today's students how to effectively design experiments, equipping them with the skills they need to become tomorrow's top researchers. Employing a refreshingly approachable and articulate style, the text explains the essential elements of experimental design in clear, practical terms, so that students can grasp and apply even the most challenging concepts, including power analysis and pseudoreplication. In addition, it emphasizes the interrelatedness of experimental design, statistics, and ethical...

Design and Analysis of Experiments

Design and Analysis of Experiments
by Douglas C. Montgomery (Author)


The eighth edition of Design and Analysis of Experiments continues to provide extensive and in-depth information on engineering, business, and statistics-as well as informative ways to help readers design and analyze experiments for improving the quality, efficiency and performance of working systems.  Furthermore, the text maintains its comprehensive coverage by including: new examples, exercises, and problems (including in the areas of biochemistry and biotechnology); new topics and problems in the area of response surface; new topics in nested and split-plot design; and the residual maximum likelihood method is now emphasized throughout the book.



Experimental Design: Procedures for Behavioral Sciences (Psychology)

Experimental Design: Procedures for Behavioral Sciences (Psychology)
by Roger E. Kirk (Author)


Written by a renowned psychologist Roger E. Kirk of Baylor University, this classic text provides the graduate student in experimental design with detailed coverage of the designs and techniques with the greatest potential use in behavioral research. Kirk's book is known for its emphasis on the logical rather than the mathematical basis of experimental design; for its in-depth exploration of the relationship between analysis of variance and regression analysis; for its introduction of the concept of building block designs; and for its comprehensive scope that describes all of the ANOVA experimental designs that are potentially useful in the behavioral sciences and education.

Experimental Design and Data Analysis for Biologists

Experimental Design and Data Analysis for Biologists
by Gerry P. Quinn (Author), Michael J. Keough (Author)


This essential textbook is designed for students or researchers in biology who need to design experiments, sampling programs, or analyze resulting data. The text begins with a revision of estimation and hypothesis testing methods, before advancing to the analysis of linear and generalized linear models. The chapters include such topics as linear and logistic regression, simple and complex ANOVA models, log-linear models, and multivariate techniques. The main analyses are illustrated with many examples from published papers and an extensive reference list to both the statistical and biological literature is also included. The book is supported by a web-site that provides all data sets, questions for each chapter and links to software.

Experimental and Quasi-Experimental Designs for Generalized Causal Inference

Experimental and Quasi-Experimental Designs for Generalized Causal Inference
by William R. Shadish (Author), Thomas D. Cook (Author), Donald T. Campbell (Author)


This long awaited successor of the original Cook/Campbell Quasi-Experimentation: Design and Analysis Issues for Field Settings represents updates in the field over the last two decades. The book covers four major topics in field experimentation:

Research Design: Qualitative, Quantitative, and Mixed Methods Approaches, 4th Edition

Research Design: Qualitative, Quantitative, and Mixed Methods Approaches, 4th Edition
by John W. Creswell (Author)


The eagerly anticipated Fourth Edition of the title that pioneered the comparison of qualitative, quantitative, and mixed methods research design is here! For all three approaches, Creswell includes a preliminary consideration of philosophical assumptions, a review of the literature, an assessment of the use of theory in research approaches, and refl ections about the importance of writing and ethics in scholarly inquiry. He also presents the key elements of the research process, giving specifi c attention to each approach. The Fourth Edition includes extensively revised mixed methods coverage, increased coverage of ethical issues in research, and an expanded emphasis on worldview perspectives.

Statistics for Experimenters: Design, Innovation, and Discovery, 2nd Edition

Statistics for Experimenters: Design, Innovation, and Discovery, 2nd Edition
by George E. P. Box (Author), J. Stuart Hunter (Author), William G. Hunter (Author)


A Classic adapted to modern times Rewritten and updated, this new edition of Statistics for Experimenters adopts the same approaches as the landmark First Edition by teaching with examples, readily understood graphics, and the appropriate use of computers. Catalyzing innovation, problem solving, and discovery, the Second Edition provides experimenters with the scientific and statistical tools needed to maximize the knowledge gained from research data, illustrating how these tools may best be utilized during all stages of the investigative process. The authors’ practical approach starts with a problem that needs to be solved and then examines the appropriate statistical methods of design and analysis. Providing even greater accessibility for its users, the Second Edition is thoroughly...

© 2015 BrightSurf.com