Well, mannequins lack the warmth and life of a real person. Their cold, lifeless appearance can be quite menacing, especially when they are arranged in a way that seems to suggest some sort of hidden intention. For example, a group of mannequins all facing one direction in an empty room can make you wonder what they are 'looking' at, and that unknown factor is what makes these stories so frightening.
Its unexpected movements. Like in the department store story, when the mannequin moved closer to the girl, it was very unexpected and that's what made it scary.
The uncanny valley effect. Mannequins look almost human but not quite, which makes our brains register them as something off - putting. Their stillness and blank expressions can suddenly seem menacing in a spooky context.
Mannequins are inherently creepy because they look like humans but lack the essence of life. They have a still, lifeless appearance which can be disturbing. In a scary story, this lack of life can be subverted, making them seem to have a malevolent life of their own. It plays on our fear of the uncanny, things that seem almost human but not quite.
The unknown elements in 21 scary stories often make them frightening. When we don't know what's lurking in the dark or what will happen next, it creates fear.
Often, it's the combination of elements. It could be the setting, like a dark and isolated place in the stories. And the characters' vulnerability. If the main character in one of the 7 stories is all alone in a spooky old mansion with no way to escape, that's pretty frightening. Also, the use of suspense, like when the story builds up to a big scare moment but keeps you in suspense for a while.
The element of the unknown. In these stories, things happen that can't be easily explained. It's like a strange noise in the middle of the night with no obvious source. That makes our minds race with all kinds of scary possibilities.
The element of the unknown. For example, when there are strange noises in a story but no clear explanation of what's causing them. It makes the reader's imagination run wild, which is a big part of what makes it scary.
The way they play on our fears. A lot of the stories in '50 scary stories' involve common fears such as the fear of the dark, being alone, or something evil lurking just out of sight. They build up the tension slowly, making you feel more and more on edge until the big scare comes. For instance, there are stories where a character is home alone at night and starts to notice small, unexplainable things happening around them, like doors opening slightly by themselves. This gradually makes the reader or listener feel very uneasy. Another aspect is the use of vivid descriptions. When the author describes a spooky location, like a decrepit old cemetery with broken tombstones and mist swirling around, it really sets the mood and makes it scarier.
The stories in '67 scary stories' are often frightening because they play on our deepest fears. Fears of the dark, of being alone, of the supernatural. For instance, a story where a person is alone in a big, empty building at night and starts to feel that there are other 'things' there with them. It builds up the tension and makes our hair stand on end. Also, the vivid descriptions in the stories make the scary scenes seem real. They describe the coldness of a haunted place, the creepy sounds, and the menacing atmosphere in such detail that it's easy to get scared just by reading it.
The element of the unknown. In these stories, things happen without explanation. For example, a character might suddenly feel a cold hand on their shoulder in an empty room. There's no obvious cause, and that makes it scarier. It plays on our natural fear of things we can't understand.