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Scientific Reasoning

One thing is common to all forms of science: an ultimate goal to know. Curiosity and inquiry are the driving forces for the development of science. Scientists seek to understand the world and the way it operates. To do this, they use two methods of logical thinking: inductive reasoning and deductive reasoning.

Inductive Reasoning

Inductive reasoning is a form of logical thinking that uses related observations to arrive at a general conclusion. This type of reasoning is common in descriptive science. A life scientist such as a biologist makes observations and records them. These data can be qualitative or quantitative, and he or she can supplement the raw data with drawings, pictures, photos, or videos. From many observations, the scientist can infer conclusions (inductions) based on evidence.

brain-scan

Image Attribution: “Brain scan,” by US Air Force Flickr via Wikimedia Commons (public domain)

Inductive reasoning involves formulating generalizations inferred from careful observation and the analysis of a large amount of data. Brain studies provide an example (see image above). In this type of research, scientists observe many live brains. They do this while people are doing a specific activity, such as viewing images of food.

Scientists then predict the part of the brain that “lights up” during this activity to be the part controlling the response to the selected stimulus, in this case, images of food. The “lighting up” of the various areas of the brain is a consequence of excess absorption of radioactive sugar derivatives by active areas of the brain. A scanner observes the resultant increase in radioactivity. Then, researchers can stimulate that part of the brain to see if similar responses result.

Deductive Reasoning

Deductive reasoning or deduction is the type of logic used in hypothesis-based science. In deductive reason, the pattern of thinking moves in the opposite direction as compared to inductive reasoning. Deductive reasoning is a form of logical thinking that uses a general principle or law to forecast specific results. From those general principles, a scientist can extrapolate and predict the specific results that would be valid as long as the general principles are valid.

climate-change

2015 was the warmest year since modern record-keeping began in 1880. This is according to analysis by NASA’s Goddard Institute for Space Studies. Image Atrribution: “NASA 2015 Record Warm Global Year Since 1880,” by NASA via Wikimedia Commons (public domain)

Studies in climate change (see image above) can illustrate this type of reasoning. For example, scientists may predict that if the climate becomes warmer in a particular region, then the distribution of plants and animals should change. Scientists have made and tested these predictions, and they have found many such changes, such as the modification of arable areas for agriculture, with change based on temperature averages.

Examples of Scientific Reasoning

The following are some examples of inductive and deductive reasoning (see image below).

scientific-reasoning

Scientists use two types of reasoning, inductive and deductive reasoning, to advance scientific knowledge. As is the case in this illustration, the conclusion from inductive reasoning can often become the premise for inductive reasoning. Image Attribution: OpenStax Biology, CC BY 4.0

Examples of Inductive Reasoning

Drawing a general conclusion from a number of observations:

  1. All flying birds and insects have wings. Birds and insects flap their wings as they move through the air. Therefore, wings enable flight.
  2. Animals as diverse as humans, insects, and wolves all exhibit social behavior. Therefore, social behavior must have an evolutionary advantage.

Example of Deductive Reasoning

Predicting specific results from a general premise:

  1. Insects generally survive mild winters better than harsh ones. Therefore, insect pests will become more problematic if global temperatures increase.
  2. Chromosomes, the carriers of DNA, separate into daughter cells during cell division. Therefore, DNA is the genetic material.

Two Pathways of Scientific Study

Both types of logical thinking are related to the two main pathways of scientific study: descriptive science and hypothesis-based science. Descriptive (or discovery) science, which is usually inductive, aims to observe, explore, and discover. On the other hand, hypothesis-based science, which is usually deductive, begins with a specific question or problem and a potential answer or solution that can be tested. The boundary between these two forms of study is often blurred, and most scientific endeavors combine both approaches. The fuzzy boundary becomes apparent when thinking about how easily observation can lead to specific questions.

hook-and-loop-fastener

Image Attribution: Top left – “Velcro Hooks,” by Alexander Klink, CC BY 3.0; Top right – “Velcro Loops,” by Alexander Klink, CC BY 3.0; Bottom left – A burr. This fruit attaches to animal fur via the hooks on its surface to improve distribution. Velcro is an example of a biomimetic invention which has copied burrs and uses small flexible hooks to reversibly attach to fluffy surfaces. By Zephyris, CC BY-SA 3.0; Bottom right – “Sneakers velcro with hook and loop fastener,” by Flickr EverJean, CC BY 2.0.

For example, in 1941, Swiss engineer George de Mestral observed that the burr seeds that stuck to his clothes and his dog’s fur had a tiny hook structure. On closer inspection, he discovered that the burrs’ gripping device was more reliable than a zipper. He eventually developed a company and produced the hook-and-loop fastener popularly known today as Velcro (see image above). Generally, descriptive science and hypothesis-based science are in continuous dialogue.

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  • Solomonking

    which one among the two form of science approach; inductive and deductive method of science plays a bigger role in most of the new discoveries and innovations witnessed in the world today?

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    1. In my opinion, both inductive and deductive forms of scientific reasoning play important roles in science. However, it seems to me that we do more of deductive reasoning to come up with many of today's innovations. We begin by identifying a specific question or problem, then we use the general proven scientific principles or laws to deduce a potential answer or solution that can be tested. However, for new scientific principles to be established, we need to do more of inductive reasoning (where we explore further and use related observations to arrive at general conclusions).