LAB 7: THE SCIENTIFIC METHOD
Making an observation and asking an interesting question
The first steps in the scientific method include making an observation, doing some
background research on the topic, and then identifying an interesting question based on
your observation. Observations may arise from reading or from first-hand experience. For
example, you may have watched your dog frequently urinate while you're on walks. This
leads to the question: Why does my dog urinate when we're on walks?
There are many possible explanations for this behavior. Among the possibilities are that
the dog avoids urinating in its own space (your yard), that there is something physiological
about walking that stimulates urine production, or that that urination is a way of scentmarking territories, just to name a few.
ACTIVITY I: CRICKET BEHAVIOR OBSERVATIONS
For this activity, you will do some preliminary observations on crickets to become familiar
with their behaviors and to help you develop a question that you would like to test.
Crickets have become a model organism for a wide range of studies, including studies on
aggression, territoriality, sexual behavior, development, and communication. Working in
groups of 2-3, determine an area of cricket behavior that you are interested in
investigating for this experiment.
At the front of the classroom you will find an array of materials that you can use, as well
as male and female crickets of various sizes, stages of development, wing morph (long or
short wing), and hunger (some have been starved for several days, others have been
provided unlimited access to food). For this portion, you will need a plastic cage and a
stopwatch, as well as 1 or 2 crickets. Choose crickets appropriate for what you are
interested in testing. For example, if you want to investigate sexual behavior, you should
take a male and a female. Alternatively, if you want to investigate male-male competition,
you may want to place two males in together. If you want to determine how hunger affects
activity budgets, you will need a single cricket and a piece of food. Do not let these
examples limit what you investigate, be creative! If you choose to put two crickets in
together, make sure to mark one of them on their pronotum using a paint pen so that you
can tell the difference between them.
Once you have your materials, begin by you and your group members observing the same
crickets, at the same time, for 5 full minutes. Do not talk you’re your partners during this
time (you will compare notes later), but focus on recording all the cricket behaviors you
observe. If you have 2 crickets in together, write down which cricket did each behavior.
For example, if you see one cricket move, then groom itself, the move again, you can
write “#1 move-groom-move”.
Observed cricket behaviors
When you are done with the 5 minutes of observation, answer the following questions:
How did your observations compare to those made by your partners?
Did you agree/disagree on what to name certain behaviors?
Did you see any patterns of behavior that you can use to develop an interesting question
about cricket behavior?
Formulating a hypothesis
To take the possible explanations for your observations and determine which answer is
mostly likely correct, you need to formulate the explanations into hypotheses. A
hypothesis is basically a prediction about the outcome of an experiment. A typical
hypothesis will be in the following general form: “If…then…because”. You can use this
format to develop hypotheses that relate directly to your experiment. For example, “If we
go on a walk, then my dog will frequently urinate because urination is a way of scentmarking territories.”
More formally, a hypothesis is a statement of an experimental result that supports an
answer to the question. It is usually paired with a null hypothesis, which does not support
that answer. The null hypothesis (Ho) is the expectation that there is no effect of whatever
we're testing. The alternative hypothesis (Ha) is the "positive" result - for example, a
difference between a control and on experimental group of animals.
So, taking the dog urination example a step further, you might decide that you can gain
insight into the larger question by collecting dog urine and pouring measured amounts at
the base of trees. Your hypotheses would then be:
Ho : If the urine from another dog is present on a tree, then it will have no effect on
the urination behavior of my dog because urination is not used to mark
territories.
Ha : If the urine from another dog is present on a tree, then it will increase the
likelihood of my dog urinating at the base of the tree because urination is used
to mark territories.
You can see that this hypothesis is much narrower than the original question, and also
much more specific than the various answers we listed. The hallmarks of a good
hypothesis are that: (1) the hypothesis is directly testable and (2) the result of testing the
hypothesis will give you insight into the original question.
One very important pitfall to avoid is deciding what you think the answer to the question
is before you test any hypotheses. Good scientists never set out to "prove" anything. One
of the intriguing aspects of science is that the results of experiments may be entirely
unexpected. Being open to unexpected results, and to modifying established theories if
newly collected data does not fit them, is a key characteristic of good scientists.
ACTIVITY II: FORMULATING A HYPOTHESIS OF CRICKET BEHAVIOR
Develop a null and alternative hypothesis on the cricket behaviors you observed in the
previous section (Remember to use the proper format – “If…then…because…”).
H0 :
Ha :
Developing your experimental design
Testing your hypothesis can involve observation, experimental manipulation, or both. The
key here is to develop a way to test it that is feasible, without too much expense or time.
You should make sure that you have enough individuals to properly test your hypothesis,
and you should measure something that will provide quantitative information to analyze.
A good experimental design isolates the effect that a single variable (i.e., the independent
variable) has on a second variable (i.e., the dependent variable) while holding all other
variables constant. It is important to attempt to control any other variables that may
confound your results. For example, you might hypothesize that plants grow more when
exposed to sunlight, and test your hypothesis by comparing growth of plants on sunny and
cloudy days. Unfortunately, cloudy days are also likely to be cooler and more humid than
sunny days, so any difference in the growth might be related to temperature or humidity,
rather than sunlight. To test that sunlight is a cause of plant growth, you would need to
carefully control all other variables that might influence growth. In animal behavior, it is
often difficult to maintain precise control over the myriad of internal (physiological and
genetic) and external (social and ecological) factors that might affect behavior;
consequently tests of causation are sometimes elusive in studies of behavior.
ACTIVITY III: DESIGNING AN EXPERIMENT ON CRICKET BEHAVIOR
What is the independent variable (manipulated variable) that you are testing?
What is the dependent variable you are testing (response variable)?
What variables must be kept constant for this to be a controlled experiment?
List the materials you will need to complete this experiment.
Outline the procedure you will follow to conduct this experiment. Be specific.
Conducting the experiment
An experiment always looks straightforward on paper, but in practice there are snags and
unanticipated problems. Animal subjects are not always cooperative and they behave in
unexpected ways. Unexpected contingencies mean that projects often take more time
than originally planned. Invariably, as you start work on your project, you will get bogged
down in the nitty-gritty details of your experiment and may lose sight of just what it was
that you were trying to find out. You should frequently refer back to your original
hypothesis to ensure that your project remains on track even if you need to modify your
experiments as you proceed. Be sure to include sufficient replication in your study so that
you may draw statistically meaningful conclusions from your data. First, maintain
consistency in the methods you use. This is especially important if more then one person
is collecting the data. If two people collect data differently, than differences in the results
may be due to biases in data collection and not due to the intended treatment effects.
Data collected using variable methods or inconsistent units of quantification are extremely
difficult to analyze.
ACTIVITY IV: CONDUCTING AN EXPERIMENT ON CRICKET BEHAVIOR
Create a data table to display your results
Use the data you have collected to create a graph. Include a title, axis labels, units, and a
scale.
Drawing conclusions
Scientists draw conclusions by examining the data from their experiment, evaluating it
critically, and relating it back to their original hypotheses. The results from an experiment
may support the hypothesis, support only part of the hypothesis, or refute the hypothesis.
In all cases, scientists must reflect on their data to determine if the experiment was in any
way flawed, such that the results should not be trusted. Reasons for flaws are numerous,
including poor inter-observer reliability, lack of appropriate controls, the presence of
confounding variables, or incorrect assumptions.
If the experimental design and data collection are not flawed, scientists can then use their
results to draw conclusions about their hypotheses and suggest future avenues of research
that are needed to understand the broader research question at hand. Conclusions can be
surprising and unexpected, and the completion of one experiment often results in the start
of several more. Being open to unexpected results, modifying hypotheses, and
investigating these new hypotheses using additional experiments are key characteristics of
good scientists.
ACTIVITY V: DATA INTERPRETATION AND CONCLUSIONS
What does your data show? Be specific and descriptive.
Did the results of your experiment validate you hypothesis?
What other variables might affect the cricket behaviors that you investigated?
If you could do this experiment over, what would you change?
If you could do a follow-up experiment, what would you test next?