Just as users can now pay to promote their newsfeed stories, a user could pay to have his or her message arrive in another person’s primary inbox, as opposed to the “other” inbox, where messages deemed less relevant by Facebook’s social and algorhithim indicators would go instead. The company explained the test, which is rolling out to a small percentage of users, in a blog post Thursday:

“Today we’re starting a small experiment to test the usefulness of economic signals to determine relevance. This test will give a small number of people the option to pay to have a message routed to the Inbox rather than the Other folder of a recipient that they are not connected with.

Several commentators and researchers have noted that imposing a financial cost on the sender may be the most effective way to discourage unwanted messages and facilitate delivery of messages that are relevant and useful.”

For instance, while users will mostly only see messages from friends and friends of friends in their primary inbox, if someone wanted to contact them for business purposes but had no friends in common, that person could pay to have the message delivered to the primary inbox rather than the “other” inbox. AllThingsD reports that the messages could cost only a dollar.

The company also announced new filtering that lets users pick which messages will land in their primary and “other” inboxes. With “basic filtering,” users will see messages from friends and friends of friends in their primary inbox, and people who turn on “strict filtering” will see “mostly” messages from friends, the company wrote.

The update comes as Facebook works to improve and expand Messenger and the integration of a user’s contacts and @facebook.com email address further into daily communication, while also figuring out how to monetize for the service. It’s an interesting question that the company will test out: Would you pay to improve the chances that your email gets read?

Related research and analysis from GigaOM Pro:
Subscriber content. Sign up for a free trial.

• How social discovery is transforming entertainment
• Flash analysis: the future of Yahoo
• Social Inbox vs. The Future of Email

Priority Inbox, which attempts to deliver the most relevant emails to the top of a user’s inbox screen, combines the behaviors of all Gmail users with your personal preferences and behaviors to deliver an inbox where your most important mail gets read first.

It’s as if your doctor could compare your physical complaints with all of the symptoms experienced by people everywhere in the world, in order to deliver a diagnosis in a few seconds. Not impressive if you have a cold, but if you suffer from a rare disorder, it’s amazing. The paper is chock full of math and explanations of how Google does this at scale (sharding databases and using Bigtable across tens of thousands of servers), but the crux of the matter is Google trying to apply machine learning to determine what each Priority Inbox user cares most about. To do that requires a computer connected to the cloud, and Google’s back-end servers. It’s an illustration of how massive computing power in the cloud and a client device can interact in ways that benefit users.

The biggest challenge isn’t necessarily the huge data crunching on the back end; it’s accounting for what the paper’s authors and statisticians call “noise,” and what I call the oh-so-human tendency to do what we want, not what’s most productive. For example, in email, we waste a lot of time and productivity opening silly emails about Lindsay Lohan’s latest escapades while ignoring those from our boss:

Opening a mail is a strong signal of importance for our metric, but many users open a lot of mail that is “interesting” rather than “important”. Also, unlike spam classification, users do not agree on the cost of a false positive versus a false negative. Our experience showed a huge variation between user preferences for volume of important mail, which can not be correlated with their actions.”

The challenge for machine learning is to calculate the signal from the noise on a massive scale in real-time, so your LiLo emails get sent to the bottom of the stack, but can still be read.

The researchers say that for Googlers who receive similar volumes of mail, Priority Inbox users spend 6 percent less time reading mail overall, and 13 percent less time reading unimportant mail. So while Priority Inbox may end up making you more productive, you might have less to chat about at the virtual water cooler. Unless you use those time savings to hang out on Twitter.

Do you use Priority Inbox? Do you think it makes you more productive?

Related content from GigaOM Pro (sub. req.):

• Enabling the Web Work Revolution
• Report: The Real-Time Enterprise
• Who Owns Your Data in the Cloud?

The Gmail team has also tweaked Priority Inbox’s algorithm so that it is now quicker to respond to manual corrections, so it should be able to learn which emails you consider to be important faster, too.

Note: I’m only seeing these changes on my Gmail account, so it looks like they haven’t been rolled out to Google Apps users just yet.

Google says that Proirity Inbox users spend, on average, 15 percent less time reading emai compared to non-Priority Inbox users, but how are you finding it — is it a time saver?

Related content from GigaOM Pro (sub. req.):

• Social Inbox Vs. the Future of Email
• Email: The Reports of My Death are Greatly Exaggerated
• Report: The Real-Time Enterprise

The company today is launching a new feature (in beta) for its popular Gmail service – Priority Inbox – which uses machine-learning technologies and marries them to Google’s search capabilities. Keith Coleman, the Gmail product director who’s been working on the product since its birth, explained that Gmail watches for things like who’s sending or receiving messages and if those people are in your contact list, then looks at other elements, such as whether the item might be spam and if the messages belong to a mailing list. It also peers into headers to make better sense of the message and give it more context.

The Priority Inbox allows important emails to surface and stay up top, pushing the less relevant stuff into the background. When the Priority Inbox fails, well, you can train it by using the +/- buttons that are part of the new menu.

(Full description from Google Blog is below.)

Now, I’m not a big fan of web-based email. I prefer the comforts of Mail.app desktop software client. By using a combination of rules, smart mailboxes and some specialized and custom scripts, I’ve beaten my email inbox into submission. It’s not that I have much of a choice; with over 1500 emails a day, I’m at risk of losing important messages, as well as spending too much time on irrelevant stuff. My email system is admittedly held together by the proverbial Band-Aid, but for me it works.

Nevertheless, for the past three days, I’ve been forcing myself to use Google Apps’ web interface, with Priority Inbox turned on. The feature is impressive and fantastic, and works as effectively as Google’s spam filters. In fact, it works so well that you almost forget it’s still in beta and hasn’t been a standard feature. Google’s been testing it internally with 10,000 Googlers and few non-Googlers. The feature has impressed me enough that I’m considering abandoning my own methodology in favor of this web-based marvel.

On a typical day, I won’t bother with the release of new features of software or a web service, but for this one, I’ve made an exception. Information overload and the perilous state of email are two issues very near and dear to me. For past five years, I’ve been writing and arguing about a whole new way of thinking about email, because what we have doesn’t seem to work. (Related: All Hail The Gmail.)

“What we want to do is give people some of their time back and with this new product we are starting to make a dent, “ Coleman said. We need help: According to research firm The Radicati Group, a typical corporate user sends and receives about 110 messages every day, while nearly 294 billion emails are sent every day. The average number of corporate emails sent and received per person per day will climb to 228 before 2010 is over. Those are some scary statistics, especially because email is now supplemented by even more data sources like Facebook and Twitter, only adding to what has become the new malaise: infobesity.

Gmail is off to a good start!

What is Priority InBox?

Priority Inbox is a new view of your inbox that helps you focus on your most important messages. It’s based on the belief that personal data is following the trend of web data—while manual organization alone worked initially (e.g., organizing websites into directories), algorithmic solutions (e.g., web search) have taken over as information has exploded in volume. Just as Gmail has always automatically filtered the bad stuff into the “spam” folder, it now also highlights the good stuff. It’s like your personal assistant, helping you focus on the messages that matter without requiring you to set up complex rules. Priority Inbox splits your inbox into three sections: “Important and unread,” “Starred” and “Everything else” (Google Blog)