Since its creation in 2014, the 'Scary Signs' subreddit has amassed more than 379K members who are eager to share the daunting messages they come across in every corner of the world. Nearly every post consists of terrifying or confusing signs that warn us of potential hazards up ahead and uneasy consequences we will face if we refuse to obey.

While we're used to seeing safety signs and not batting an eye, people on this online community prove that some of them have a slightly threatening nature that everyone should take notice of. After all, most of us are hoping to avoid falling into "the drowning machine", getting attacked by aggressive geese, or encountering a venomous snake that's missing from its exhibit.

Yet, there seem to be many factors that can make people disregard even the most frightening messages. Maybe you're an adrenaline junkie looking for new adventures every chance you get. Perhaps you think the sign is scarier than the danger itself. I mean, it's better to be safe than sorry, but who really wants to be told to watch out for falling deer? How often does that really happen?

Marc Green, Ph.D., is a human factor expert who has extensive experience in perception, attention, human factors, and related areas. According to him, warning signs often fail to change people's behavior. They can either go unnoticed or, more often than not, they are seen but ignored by the viewer. "For many years, designers focused their concern on sensory aspects of warnings: color, shape, location, pictures vs. text, size and so on. However, recent research suggests that effective warning design depends as much on the contents of the viewer's head as on the contents of the warning's message," he explained.

You see, when people stumble upon alarming messages, they then have to make a decision whether or not to comply. But let's not forget that people who are the intended audience of these signs are not blank slates. They rather start with a thought process containing three components: "First, the viewer has general knowledge about the world and how it works. Second, s/he has a set of beliefs and expectations based on experience with the same or similar environment, product or technology."

"Lastly, the viewer enters the situation with a goal and strategy for achieving that goal," Green continued. "The goal can be specific ('I want to arrive at my destination as soon as possible') or more diffuse ('I want to feel good about myself')." So to create an effective warning sign, the designer must understand what the observer "brings to the table".

As viewers, we’re aware that safety signs are placed there for our own benefit. Their purpose is to draw our attention to important information that might prevent us from doing harm to ourselves or the people around us. Unfortunately, sometimes they are less likely to be effective when they are placed in the wrong area or use vague messaging. This could lead to tragic accidents, so it’s always best to make sure the sign will be crystal clear to virtually anyone.

However, even when signs are compelling and tick every box on the list, we humans have a tendency to overlook them. Green explained that when a warning tells us to refrain from behavior that would enable us to quickly achieve our goal, we then make a cost-benefit analysis. "In some cases, the viewer might lose the goal altogether ('No Smoking' signs), or exert more effort ('Detour' signs)," he mentioned some examples of the cost.

When it comes to benefits, they can be practical (like injury avoidance), and psychological. "A driver deciding whether to comply with a speed limit sign might calculate the costs of arriving later," he added. But one benefit of compliance is feeling safe and less anxious, like thinking "I won't be as likely to get in an accident," or "I won't have to spend time and effort looking for a radar trap." Other psychological advantages could be the sense of being "a good citizen" or "a team player," Green argued.

Another factor that affects how we see the size of the benefits is the perception of danger, which has two elements — hazard and risk. The viewer of the warning sign must take them into account when making the calculation. "If the person believes that there is great danger, then s/he will see a larger benefit in compliance. Conversely, perception of small danger means low benefit and compliance will decrease," he explained.

Lastly, our personal, social, and cultural backgrounds also affect our decision-making. Green explained that even when two people make the same cost-benefit analysis, they could go two different ways — one might ignore the sign while the other doesn't. "People accept different danger levels, have different attitudes about their ability to control danger and are differentially affected by social and cultural norms," the expert added.

So for warning signs to be persuasive, designers should focus more on the psychological factor. Sure, the bright glaring colors and terrifying symbols catch our attention and might stop us from falling into dangerous threats, but harmony between human behavior and design would reduce accidents even further.