Games like The Watson-Scott Test
Games like The Watson-Scott Test include Five Nights at Freddy's, Firework, No, I'm not a Human, Outlast 2, and Mouthwashing. We matched them by the tags players give The Watson-Scott Test on Steam (Psychological Horror, Indie, Horror, Text-Based, and Interactive Fiction): closest matches first, and among equally close ones the better-known games.

Five Nights at Freddy's
Shared: Horror · Psychological Horror · Indie

Firework
Shared: Indie · Horror · Psychological Horror

No, I'm not a Human
Shared: Psychological Horror · Horror · Indie

Outlast 2
Shared: Psychological Horror · Horror · Singleplayer

Mouthwashing
Shared: Psychological Horror · Horror · Indie

Tiny Bunny
Shared: Horror · Psychological Horror · Atmospheric

Outlast
Shared: Horror · Psychological Horror · Atmospheric

Sally Face - Episode One
Shared: Psychological Horror · Indie · Horror

Stories Untold
Shared: Horror · Text-Based · Indie

Little Nightmares
Shared: Horror · Atmospheric · Indie

MiSide
Shared: Psychological Horror · Horror · Singleplayer

Poppy Playtime
Shared: Horror · Psychological Horror · Singleplayer

Milk inside a bag of milk inside a bag of milk
Shared: Psychological Horror · Horror · Interactive Fiction

Layers of Fear (2016)
Shared: Psychological Horror · Horror · Atmospheric

Little Nightmares II
Shared: Horror · Psychological Horror · Singleplayer

Blair Witch
Shared: Psychological Horror · Horror · Indie

Five Nights at Freddy's 2
Shared: Horror · Psychological Horror · Indie

Resident Evil 7 Biohazard
Shared: Horror · Psychological Horror · Singleplayer

SOMA
Shared: Psychological Horror · Horror · Atmospheric

Visage
Shared: Psychological Horror · Horror · Indie

Little Misfortune
Shared: Psychological Horror · Indie · Horror

DISTRAINT: Deluxe Edition
Shared: Psychological Horror · Indie · Horror

Getting Over It with Bennett Foddy
Shared: Psychological Horror · Horror · Singleplayer

SILENT HILL 2
Shared: Psychological Horror · Horror · Atmospheric