- Okay, has anyone else noticed that your For You page
has been a little too accurate lately?
It hasn't been things that I'll google
or I talk about.
It's been thoughts.
- TikTok knows everything about us.
♪ Hold up, don't scroll ♪
♪ Lemme ask you something first ♪
♪ Can someone please explain ♪
♪ How this algorithm works ♪
- [Narrator] TikTok users often wonder
how the world's fastest-growing social network seems
to know them so well.
- Is TikTok secretly listening to us
while we're watching videos?
I don't know.
(upbeat music)
- [Narrator] The answer to how this app gets to know you
so intimately is a highly secretive algorithm,
long guarded by TikTok's
China-based parent company, ByteDance.
- TikTok has been so successful
in terms of implementing their algorithms.
- TikTok's algorithm could influence the thinking
of US youth.
(upbeat music)
- [Narrator] To understand how it knows users so well,
The Wall Street Journal created
over 100 automated TikTok accounts or bots
that watched hundreds of thousands of videos on the app.
We also spoke to current and former executives
at the company.
Officially, the company says that shares,
likes, follows and what you watch all play a role
in what TikTok shows you.
We found that TikTok only needs one
of these to figure you out.
How long you linger over a piece of content.
Every second you hesitate or rewatch,
the app is tracking you.
- I just wanna quiet the noise.
- [Narrator] Through this one powerful signal,
TikTok learns your most hidden interests and emotions.
And drives you deep into rabbit holes of content
that are hard to escape.
(noise of voices)
♪ I'm happy, happy guy ♪
♪ Oh, just a happy, happy, happy ♪
- [Narrator] The TikTok experience starts
the same way for everyone.
Open the app and you'll immediately see an endless string
of videos in your For You feed.
Take this new user,
a 24-year-old from Henry County, Kentucky.
(jumbled music plays)
TikTok starts by serving the account a selection
of very popular videos vetted
by app moderators.
Is this person religious?
- Because I still have a purpose.
And you still hold a plan for my life.
- [Narrator] Do they wanna participate in viral dances.
(upbeat music)
♪ Hey, hey, who ♪
(upbeat music)
- [Narrator] Are they feeling down lately?
- [Narrator] Just remember, I loved you once.
And that love goes for a friend,
family, or any relationship.
- [Narrator] What TikTok doesn't know
is that the 24-year-old from Kentucky
isn't a person at all.
It's one of the bot accounts programmed
by The Wall Street Journal.
Let's call it kentucky_96.
We set up these accounts to understand
how TikTok figures out your unexpressed interests.
We assigned each bot a date of birth and an IP address,
which told TikTok their location.
None were given a gender.
We gave each bot or user interests
but those interests were never entered into the app.
The only way our users expressed their interests
was by rewatching or pausing on videos
with related hashtags or images.
Some were into extreme sports.
Others were interested in forestry.
Or dance.
Or astrology.
- I'm not the babysitter, I'm not the parent.
- [Narrator] Or some other topic.
- [TikToker] Keep scrolling if you hate animals.
- [Narrator] For all our accounts,
we found that TikTok draws users in at first
by serving a wide variety of videos.
Many with millions of views.
Then as the algorithm sees what you respond to,
the selection of videos and the view counts
can get lower and lower
with fewer of them vetted by moderators
to see if they violate TikTok's terms of service.
We reviewed our experiment
and its results with a data scientist,
an algorithm expert, Guillaume Chaslot,
a former Google engineer
who worked on YouTube's algorithm.
He's now an advocate for algorithm transparency.
The says TikTok is different
from other social media platforms.
- The algorithm on TikTok can get much more powerful
and it can be able to learn
your vulnerabilities much faster.
- [Narrator] In fact, TikTok fully learned many
of our accounts' interests in less than two hours.
Some it figured out in less than 40 minutes.
- [Guillaume] On YouTube, more than 70% of the views come
from the recommendation engine.
So it's already huge.
But on TikTok, it's even worse.
It's probably like 90-95%
of the content that is seen
that comes from the recommendation engine.
(dramatic music)
- [Narrator] This is a visualization made
from hashtags attached to the videos our bots watched.
Think of it as a partial view
of the universe of TikTok content.
Here's where we found dance videos,
over here are the cooking videos.
The spindly arm stretching out of the center
represent niche content areas.
This arm starts with general videos of cute animals
but if we follow it out to the end,
we find more specific videos for enthusiast
of French bulldogs.
As kentucky_96 starts its journey,
it starts moving around within the mainstream
where TikTok is trying to puzzle out what it wants.
We programmed kentucky_96
to be interested in sadness and depression.
Let's see how long it takes TikTok to figure that out.
- [TikToker] Life doesn't happen to you,
life happens for you.
So if life is taking people away from your life,
and putting new ones in.
- [Narrator] Less than three minutes into using TikTok,
at its 15th video,
kentucky_96 pauses on this.
- [TikToker] And that love goes for a friend,
family or any relationship.
- [Narrator] Kentucky_96 watches the 35-second video twice.
Here TikTok gets its first inkling
that perhaps the new user is feeling down lately.
- [TikToker] Whoever comes, let them come.
Whoever stays, let them stay.
Whoever goes, let them go.
- [Narrator] The information contained in this single video
provided the app with important clues.
The author of the video, the audio track,
the video description, the hashtags.
After kentucky_96's first sad video,
TikTok serves another one 23 videos later.
Or after about four more minutes of watching.
- [TikToker] I'll leave you alone from now on
if that's what you want.
- [Narrator] This one is a breakup video
with the hashtag #sad.
- [TikToker] Do you why I leave you alone?
'Cause I care about your feelings more than mine.
- [Narrator] TikTok's still trying to suss out this new user
with more high view count videos.
Does the new user wanna watch videos about friendship?
(upbeat music)
(playful music)
Or to laugh at funny fail videos?
♪ Oh no, oh no, no, no, no, no ♪
- [TikToker] Nobody's gonna know.
- [TikToker] They're gonna know.
(dramatic music)
- [Narrator] Or do they like videos about home repairs?
(dramatic music)
(upbeat music)
Other information from your phone,
including location can impact the videos
that are shown in a user's feed.
- And as a Kentuckian,
I never thought I'd lose my freedom
over a virus.
- [Narrator] For instance, kentucky_96 saw lots
about Kentucky but whether or not it keeps showing you
that type of video depends on your response to it.
A TikTok spokeswoman said the app
does not listen to your microphone
or read text messages to serve you personalized videos.
(pensive music)
At video 57, kentucky_96 keeps watching a video
about heartbreak and hurt feelings.
(pensive music)
And then at video 60,
watches one about emotional pain.
(dramatic music)
Based on the videos we watched so far,
TikTok thinks that maybe this user wants
to see more about love, breakups and dating.
So at about 80 videos and 15 minutes in,
the app starts serving more about relationships.
But kentucky_96 isn't interested.
- [TikToker] Your voice, your smile,
your eyes, your laugh.
- [Narrator] The user instead pauses on one
about mental health.
Then quickly swipes past videos about missing an ex.
- [TikToker] I miss you and I like having you around.
- [Narrator] Advice about moving on
and how to hold a lover's interest.
- [TikToker] He spends more time on his phone
when he's around you.
- [Narrator] Kentucky_96 lingers over this video
containing the hashtag #depression.
- [TikToker] Something's wrong with me.
(sad music)
And these videos about suffering from anxiety.
- [TikToker] It's like a reward.
- [Narrator] After 224 videos into the bot's overall journey
or about 36 minutes of total watch time,
TikTok's understanding of kentucky_96 takes shape.
Videos about depression and mental health struggles
outnumber those about relationships and breakups.
From here on, kentucky_96's feed is a deluge
of depressive content.
93% of videos shown to the account
are about sadness or depression.
- People been lookin' at me.
I'm just like what you looking at?
- [Narrator] A TikTok spokeswoman said
that some of the remaining 7% of videos
are to help the user discover different content.
But for kentucky_96, such videos were few and far between.
The majority of videos it was shown outside
of its depressive rabbit hole were ads.
A TikTok spokeswoman said that the simulated activity
generated by The Wall Street Journal's bots
is not representative of real user behavior
because humans have a diverse set of interests.
But even some of our accounts
with diverse interests rabbit holed.
We showed our data and many of the videos seen
by kentucky_96 to Chaslot.
- What we see on TikTok
is a bit the same that what we saw on YouTube.
So basically, the algorithm is detecting
that this depressing content
is useful to create engagement
and pushes depressing content.
So the algorithm is pushing people
towards more and more extreme content,
so it can push them toward more and more watch time.
- [Narrator] TikTok also says it allows you
to see less of something
by selecting the Not Interested button
but Chaslot says that's not enough.
- The algorithm is able to find the piece
of content that you're vulnerable to,
that will make you click,
that will make you watch
but it doesn't mean you really like it
and that it's the content that you enjoy the most.
It's just the content that's the most likely
to make you stay on the platform.
- [Narrator] Our bots only escaped rabbit holes
when we changed their viewing interests.
When we told one bot to stop watching videos
about ADHD, the algorithm cut back on that content.
Still, many of The Journal's bots
were rapidly pushed deep into rabbit holes.
TikTok learned our bots' most far-flung interests,
like astrology, but even bots
with general mainstream interests got pushed
to the margin as the recommendations
got more personalized and narrow.
Bots with a interest in sexual content
wound up way out here
watching hashtag #kingtok videos
about sexual power dynamics.
And our bot with a general interest in politics
wound up being served videos
about election conspiracies and QAnon.
- Impeach Biden and Kamala.
It goes from the House to the Senate.
- [Narrator] Deep in the niche worlds of TikTok,
users are more likely to encounter
potentiality harmful content
that is less vetted by moderators
and violates the app's terms of service.
- [TikToker] Make them angry and sad.
They would be so much happier without you.
- [Narrator] A TikTok spokeswoman said
that the company catches a lot of banned content,
which passes through both computer analysis
and human moderators.
It also reviews videos reported by users.
- [TikToker] Don't tell them goodbye, just go.
- [TikToker] It's not my time.
Pew.
(TikToker laughing)
- [Narrator] There's a lot of fun, silly
and life-affirming content on TikTok.
(TikToker screaming)
But while TikTok can draw out what makes you laugh.
(TikToker humming)
It can also make you wallow in your darkest box.
- Turning the pain from mental to physical works.
- [Narrator] Without ever needing to eavesdrop on you
or collect any personal information about you.
- I've never attempted suicide or anything.
I've never let it get that far.
- Whether it's on TikTok,
on Facebook, on YouTube,
we're interacting with algorithms
in our everyday life more and more.
We are training them and they're training us.
So we have to study this
so we understand it better
and we don't let it go in directions
that are harmful to society
or to certain groups of people.
(dramatic music)