For example, imagine a worker in a widget factory who is responsible for checking if all the widgets on a conveyor belt are well-made. This worker is successful in their job 99% of the time. However, when a second worker is added to the same task, and both workers are aware of the other, the accuracy rate drops to 90% because both workers assume that the other person will do a good job.
Is there a word or phrase to describe this phenomenon? It's related to "bystander effect" but not exactly it.
Since you mention the "bystander effect", I guess you're looking for a psychological term. This would be "Diffusion of responsibility", even though its prime examples are mostly taken from emergency situations:
The diffusion of responsibility refers to the decreased responsibility of action each member of a group feels when they are part of a group. For example, in emergency situations, individuals feel less responsibility to respond or call for help if they know that there are others also watching the situation - if they know they are a part of the group of witnesses
Further down the article, both "bystander effect" and "social loafing" (as mentioned by JonathanReez) are listed as two possible consequences of diffusion of responsibility.
This sounds like a case in which too many cooks spoil the soup.
This means, according to The Free Dictionary:
If too many people try to control, influence, or work on something, the final product will be worse as a result.
There is a term in software development called Brooks's Law. The idea is that adding additional personnel to a project will increase, not decrease the time it takes to complete it.
The idea is typically that the overhead of adding more people to the task is more work for the people already engaged in the task, increases the burden of communication as you don't want to make changes that impact other's work, and that knowledge of the entire system is necessary to begin working and thus the task is largely non-divisible anyway.
I've never heard it referenced outside of software development but unlike other answers doesn't come with the implication that the people involved are just doing sloppier work, its just a feature of the task.
I think the right term is social loafing, which Wiki defines as:
Social loafing is the phenomenon of a person exerting less effort to achieve a goal when they work in a group than when working alone. It is seen as one of the main reasons groups are sometimes less productive than the combined performance of their members working as individuals.
I upvoted "too many cooks spoil the broth (or soup)" because I think it most closely matches the paradoxical effect of reduced efficiency from adding people to a task.
I also thought of the Bystander Effect, but as I understand it, that effect is usually brought up about others who just stand around and do nothing - rather than doing the same thing less efficiently. But I also see that it could be used to refer to reduced efficiency or to people who want to be helpful but end up being no help due to the effect of others around them.
"Passing the buck" or "diffusion of responsibility" don't sound fitting for this kind of concept, as far as I see it. Those terms are focused mainly on people who are deliberately avoiding certain work, as opposed to two people honestly trying to do a good job but suffering a drop in efficiency as a side-effect of being put on the same task.
Finally, there is the concept of the "mythical man month." This term is from a book on software development, so it is not useful to anyone who doesn't follow software or project management jargon. But it does capture the idea that adding people to a project tends to make that project even later. This concept, however, is about training and other overhead, not about one worker assuming another will do the same task, as is presented in the question's scenario.
Therefore, assigning more programmers to a project running behind schedule will make it even later. This is because the time required for the new programmers to learn about the project and the increased communication overhead will consume an ever-increasing quantity of the calendar time available
https://en.wikipedia.org/wiki/The_Mythical_Man-Month#The_mythical_man-month
This is also known as the law of Diminishing Returns
For example, the law states that in a production process, adding workers might initially increase output. However, at a certain point the optimal output per worker will be reached. Beyond that point, each additional worker's efficiency will decrease because other factors of production remain unchanged, such the available resources.
Source: TechTarget
Less than the sum of its parts
The expression "greater than the sum of its parts" describes a situation where the combined efforts of two or more individuals exceed the sum of the capabilities of each individual. From collinsdictionary.com:
If you say that something is more than the sum of its parts or greater than the sum of its parts, you mean that it is better than you would expect from the individual parts, because the way they combine adds a different quality.
This is often used with relation to pop groups - also from collinsdictionary.com:
As individual members' solo careers have proved, each band was greater than the sum of its parts.
Accordingly, "less than the sum of its parts" is understood to describe a situation where the combined efforts of two or more individuals are less effective or of lower quality than you might expect, given the capabilities of each individual.
Revisiting the pop group example, this expression might be used where two or more successful / talented solo artists collaborate to produce a piece of music, which is judged to be underwhelming. (Naming no names...)
“Asynergy” is actually a word with the meaning “ defective coordination between parts” (https://www.collinsdictionary.com/dictionary/english/asynergy) but it has apparently been hijacked by the medical profession. Still, its meaning would be clear, and its use outside medicine could be justified as metaphorical. Similar remarks apply to “dyssynergy”.
If you prefer a less tainted word, then “anti-synergy” would be more than acceptable, not least because others have found it so - e.g.https://brill.com/abstract/book/9781848883574/BP000003. xml
The correct term is, TRAINING YOUR REPLACEMENT. When a second person is added to do the job that you were able to handle on your own, the most common sense reason for why they are there is to replace you. This will cause much dissatisfaction and resentment on the part of the initial worker, and tension between them both.
Well, in the latter case the buck doesn't stop with either one of them. So the word/term is mutual Buck passing.
Also, The Farlex Dictionary gives this idiom for such a situation:
pass the baton
To bestow one's responsibility or job upon someone else. [An allusion to a relay race in which one runner literally hands a baton to the next runner.]
I have so much work to do now that my boss has retired and passed the baton to me.
