How to read a scientific paper

What to Look For in Any Paper

• What is the main topic?• Specific introductory concepts and terms essential to

understand the context• Hypotheses!• How setup, including design of experimental and

control groups, lends validity to data interpretation• Relevant results• Conclusions drawn from results, and how results add

to current theory• Limitations and Future Studies

A.F. Russell et. al. 2007. Reduced egg investment can conceal helper effects in

cooperatively breeding birds. Science 317: 941-944

Paper is about cooperative breeding

Benefits of helpers are hard to detect

They did an experiment on helpers and mother tactics when there are

helpers

In their bird, moms lay smaller eggs when there are helpers.

Helpers make up for the small egg size with increased feeding, so

moms survive better.

If you don’t pay attention to mom, you’ll miss this advantage to

helping.

At your tables, make a list of the things the authors need to show.

Then list the evidence for how they showed them.

Divide up the work to match evidence to what they needed to

show.

Specific introductory concepts, terms and context

• What do you need to know before you can move on and understand the rest?- Cooperative breeding- Failure of previous studies to detect helper effects- Advantages to being a breeder/helper- Reasons why breeder might limit investment in eggs- Reasons why helpers’ benefit to offspring condition and survival might be masked- physiological priming or future reciprocity or rent

payment or decreased maternal investment in eggs

What are the hypotheses?

• A hypothesis must be a directional prediction that one thing causes another, for a specific biological reason.

• For example, birds have smaller territories near streams because near streams there are more insects to eat and defending a territory larger than necessary is not worth the cost.

Hypotheses

These are not exactly hypotheses, but questions. A hypothesis should give a definite prediction: “Helper number will be lower for smaller eggs because this indicates low chance of succes,” for example. Authors will not always state these explicitly, but the intro will often share their predictions, and reasoning behind them. You should try to write out the hypotheses in complete format.

Most Important Aspects of the Experimental Design

• Model Organism, and why• Type of study: experimental,

observational, comparative• Are experimental and

control groups sufficiently designed to allow the authors to pass judgment, without objection, on the hypothesis they set out to study?

• Details often can be found in figure legends

Statistical analysis

Experimental and Control Groups

Relevant Results

• Figures should be your first recourse – what does each figure show?

There are a lot of figures! What is the main idea of each one? Why is each an important contributor to the validity of the conclusions?

More Relevant Results

Which most directly support the hypotheses, and how?

Conclusions

• What are the implications of the data, placed into context?

• Did they sufficiently control the experiment to draw these conclusions, or are there confounding variables?

More Conclusions, Limitations and Future Directions

• What are some problems or questions left insufficiently addressed by this study?

• What is the next logical experiment to perform in this system?

• What are the ramifications of the results for the wider field of theory/study?

In class activity after the talk:

• Give students a copy of the paper (Russell et al. Reduced Egg investment can conceal helper effects in cooperatively breeding birds. Science 317: 941-944 (2007)

• Give them the handout on the following slide to fill out with discussion (reprint with space on page to put in answers).