For most of us, plagiarism is a morally offensive act. Whether giving a proper citation in a paper or proper acknowledgement when speaking, we think it is the right thing to give people credit for their ideas or words. In academia, citing the source of information is critical for a few additional reasons. For one, by knowing the source of the fact, idea, illustration, or conclusion, the reader/listener can vet the quality of the information: a process that is critical, complex and should not be random. Basing decisions on low quality information leads to average outcomes, at best, and certainly an increased risk of inappropriate choices.
Second, citing the source allows one to track the influence of the facts, ideas, illustrations, and conclusions generated by that source. Why is that important? As more data is gathered and as our powers of observation and analysis improve, previously found facts, ideas, illustrations, and conclusions can be proven to be inaccurate. As a result, information that is influenced by the outdated materials needs to be reevaluated or at least updated. For example, lets say there is an experiment that offers a specific procedure to measure the activity of motor units. This procedure is reproduced with statistical accuracy and becomes a standard way of measuring motor unit activity. Lets call this paper A. Now when a scientist wants to use the methods outlined in paper A to measure the recruitment of motor units in the biceps, they cite paper A as their procedural template. An experiment is designed, data is collected and analyzed, and conclusions are drawn about the recruitment of motor units in the bicep. Lets call this paper B. And lets say 24 other scientists base their experiments on paper A. However, only papers B-R cite paper A; papers S-Z do not. So we have a ton of information about the recruitment of motor units based on the findings of paper A.
Then another scientist comes along and shows that, due to improved techniques and data analysis, the findings in paper A are fundamentally flawed. This is paper ZZ. As part of writing ZZ, the authors will discuss the problems with paper A. Now anyone (readers/listeners and researchers) who relied on the data and conclusions based on paper A will have to reevaluate their findings. Since papers B-R have used paper A and cited the source, it is easy to identify the information in these papers as information that needs to be re-examined. Users of the information from papers S-Z may remain unaware of the updates and continue to operate with a flawed premise. So provenance* (the origin or history of ownership) is a critical aspect of learning, educating,and researching. In the end, it helps us stay current, advance our knowledge, and understand how to strategically modify our thinking and application of our skills.
How does one go about vetting the quality of cited sources? Well, that is a much longer and equally critical conversation.
*Thanks for the suggestion of the word provenance, Greg Mack.