Magazine subscriptions that mysteriously end up in your online shopping cart. Items with 50 people looking at them "right now" that are still for sale weeks later — these are the internet's "dark patterns".

As we spend more of our lives on the internet, it is vital to know when we're being manipulated: the design choices that nudge us into unnecessary purchases, into revealing personal information, into clicking accept when we'd rather not.

The term "dark patterns" emerged in 2010, when UK-based user experience consultant Harry Brignull took a closer look at Ryanair.

Dark Patterns to watch out for: Bait and Switch

Bait and Switch Disguised Ads

Disguised Ads Forced Continuity

Forced Continuity Friend Spam

Friend Spam Hidden Costs

Hidden Costs Misdirection

Misdirection Price Comparison Prevention

Price Comparison Prevention Privacy Zuckering

Privacy Zuckering Roach Motel

Roach Motel Sneak into Basket

Sneak into Basket Trick Questions Source: darkpatterns.org

The budget airline was notorious for cost cutting, but its website was full of what Mr Brignull saw as misdirection.

In one instance, it was designed so that customers could barely avoid purchasing insurance as they checked out. The company was later made to drop the tactic.

As Mr Brignull found more of these user experience tricks, he created an online taxonomy of around 10 dark patterns.

One of the most common examples is the "Roach Motel", he said.

You sign up for a magazine subscription, and although it may have been just a few clicks to pay, it is "a labyrinth" to cancel.

"It's manipulative, yet totally legal ... To make something slightly easier on the way in and slightly harder on the way out."

Beyond retail, entertainment platforms are not immune.

Video auto play aims to keep you glued to your screen. Social media apps often notify you of one like at a time. Why? To prod you into checking the app repeatedly.

These tactics aren't going away, and thanks to the personal data we reveal with every click and subscription, they could get even more targeted.

Why do dark patterns work?

You're not stupid: dark patterns often appeal to preferences and blind spots that are there for good evolutionary reasons.

Brendan Markey-Towler, a psychological economics researcher at the University of Queensland, said this type of manipulation has come a long way since the mad men of Vance Packard's 1957 book on advertising, The Hidden Persuaders.

"It's like comparing a rifle with a nuclear bomb."

According to Mr Markey-Towler, some dark patterns rely on our preference for the default option. "To decide to do something, especially if it's unknown, is very taxing," he said.

Companies may make use of this by asking you to actively opt-out of mailing lists, for example.

We're also vulnerable to reference points — when sites tell you: "other people have bought X" — because we look to other people to take our cues.

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It is instinctual to filter and categorise the language used on these sites. "You can say, oh 'free trial'. That means it's going to end, right?" Mr Markey-Towler said. "A trial to our mind has a beginning and an end."

The site, of course, doesn't consider your relationship finished and sends a recurring charge to your credit card. (Mr Brignull calls this "forced continuity.")

This filter is particularly relevant for the dark pattern dubbed "Privacy Zuckering" — when you're hoodwinked into sharing more personal information with a site than you meant to.

Consider the line ubiquitous in most website terms of use: "We'll share your information with third parties."

Most of the time, that means "sell your information", Mr Markey-Towler pointed out. People don't like to have their information sold, but "sharing" feels much more palatable.

Where do dark patterns come from?

Retailers have long exploited our cognitive limitations — why else would something cost $9.99? — but dark patterns are so common online they feel part of the web's DNA.

Mr Brignull suggested that they sneak into apps and websites via A/B testing.

This is when multiple formats are tested on consumers to see which best helps the company achieve its goals — whether clicks, engagement or sales.

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"You say, right, we need to get more of this action to be completed. We need these metrics to go up," he explained. "Well, let's try five different versions of this button."

If any less ethical format sneaks in — for example, a check-out process that hides costs — the deceptive version will probably win because it is tricking people into the site's desired result.

As Jeremy Keith, a UK web developer, speculated on his blog recently, "I think A/B testing is a way to institutionalise a focus on business goals — increasing sales, growth, conversion, and all of that.

"But more sales doesn't necessarily mean happy customers."

When dark patterns get personal

To extract maximum value, companies are doing their best to be relevant to your specific likes or desires.

There are fears that with increasing amounts of personal data, dark patterns could become effectively weaponised.

Imagine a website checkout process that hid costs in a way designed to thwart your unique decision-making process.

In his article "Digital Market Manipulation", Ryan Calo, associate professor of law at the University of Washington, dubbed such a future the "mediated consumer".

She approaches the marketplace through technology designed by someone else. As a consequence, firms can generate a fastidious record of their transaction with the consumer and, importantly, personalise every aspect of the interaction. This permits firms to surface the specific ways each individual consumer deviates from rational decision marking, however idiosyncratic, and leverage that bias to the firm's advantage.

This is still a blunt instrument today, but some experts argue consumer protection law will need to get savvier before it is too late. Especially as smart devices and wearables mean we can be approached anytime, anywhere.

In his work, Professor Calo suggested there may a role for regulators where the incentives of corporations to personalise their approach and the goals of consumers do not align — when it is no longer fair play.

Bodies like the Australian Competition and Consumer Commission could help, Mr Markey-Towler said, but it would be hard to demonstrate when such tactics were being used maliciously.

"There may be responsibility for the consumer to recognise that there are bad practices out there, and that means, yes, you will need to be on guard," he said.

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Mr Markey-Towler suggested the answer may be to "do a Ulysses" and pre-commit to a rational course of action — to effectively lash yourself to the mast before setting out to confront the sirens of tricky web design.

One way is to set goals: "Limit your exposure by telling your conscious brain, 'I'm only getting this one thing and I'm not getting anything else'," he advised.

In any case, why do companies need to get fancy? The old manipulations have survived remarkably well.

"I often talk to people who are looking at prices and it might say $9.99, and while they're talking to me, they'll refer to it as $9," Mr Brignull said.

"It really does work."