I have never heard of this ("most widely replicated UX result"), nor have I ever seen it to be the case on any kind of consistent basis.

In an effort to perform a minimum of due diligence, I ran a couple web searches and no relevant articles were returned.

What I do believe, is that users have difficulty understanding directories / folders as they can be represented on newer OS's as another commenter very eloquently pointed out.

However, I am highly skeptical of the claim that the population at large is simply unable to grasp the basic concept of hierarchical directories.

I only ask because I work with a huge (50k+) population of people who, based on the evidence I have from systems we manage, do seem to "get it" to varying degrees.

There's definitely a spectrum, from people who are digital slobs to neatniks who have more folders than files.

A list of Artists, Rap, Prince, or Slow songs in some mp3 management software resembles people's ideas of a "directory" better.

One thing I've noticed about these silo/tagging systems and non-savvy users is that, though the users are generally comfortable in them, they also tend to lose data completely a lot and have no idea how to find it again. They also find it very hard to understand the concept of backups because they have no sense of location for any of their data.

"File," "Folder," "Copy," "Move," "Mail," and "Trash" are a really excellent set of terms to explain this stuff easily. Did AAPL or MS come up with this? I find the only problem with them is that people don't understand why you don't end up with two files of the same name in the same folder when you make a copy (because "Copy" is more like "Copy and Move".)

edit: or copy is more like "nothing just happened," really. I think the metaphor becomes broken when you go to clipboards and pasting. Maybe the right metaphor is to make the desktop the clipboard. When people "Copy" a file, folder, or anything else, it should appear on their "Desktop" rather than a "Clipboard," where they can see it at all times, and use it as a shortcut. The desktop doesn't have to be thought of as a proper directory.

Okay, I want to move files from point A to point B. What you're supposed to use is "cut" and "paste". If I use "cut" in a text editor, the text is gone until pasted. What if I do a "cut" on files? Are they deleted? Are they put in some super-invisible temporary trash bin? Or does the OS actually do nothing until you "paste" them? Do they have the same clipboard as copied text, or a different one? If you do a "cut" on files in folder A, followed by a "paste" in folder B, followed by another "paste" in folder C, what's the result? How do cut/copy interact with shortcuts, junction points, hardlinks, or symlinks? What are the subtle semantic incompatibilities in these metaphors across different versions of Windows, PC, Mac, Gnome, KDE, etc.?

Using the GUI is a crapshoot in terms of whether what actually happens will match my intent, and I'm an expert; I can scarcely imagine what a n00b's experience must feel like. You can do things much more precisely with command-line mv, cp or xcopy, find | xargs, or writing a simple Python script with os.walk(). About the only thing I use the GUI to do is select a large number of randomly distributed files from a directory.

"Trash" is also confusing, because things don't end up there consistently. If you cut things, they don't; if you delete them from the GUI they do. If you delete things from the command line, they don't. If the things are on a removable device, the Trash doesn't get them. If you delete things within an application, who knows what happens? It depends on whether the app is coded to use whatever API routes stuff to the Trash.

I think they broke the metaphor there by even using the word "delete" at all. Make them choose between "Trash" or "Shred" and that might work.