Autism contains a wide spectrum of behaviors and conditions that typically present as difficulty with social skills and communication, as well as repetitive behaviors. There are many characteristics of autism that are relatively well-known -- such as making repetitive movements like hand-flapping or rocking (stimming), having delayed speech, and fixation on certain objects -- and there are many characteristics of autism that aren't as well-known.

No person on the spectrum is the same; two toddlers may engage in completely different behaviors and be at two different points in their development and both be diagnosed with autism. Likewise, two adults with autism may be at completely different points in their lives in terms of independence, motor skill development, and social skills.

It's called a spectrum for a reason.

Here, we want to explore some of the lesser-known characteristics of autism. Some of these behaviors are closely linked to each other, and some may be surprising. Every person on the spectrum won't display all these traits, but being aware of them can be helpful in preventing misunderstanding and, in some cases, avoiding danger.

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Inappropriate laughing or giggling

Plenty of children go through phases where they laugh inappropriately -- it's part of developing social skills and appropriate responses. However, if that phase doesn't end, it can be a lesser-known characteristic of autism.

Inappropriate laughing can be caused by a lack of communication skills, sensory sensitivity, or difficulties with high-level thinking and judgment. Someone with ASD may respond with laughter to a serious situation because they are focused on one aspect of what is happening or something in their head, or simply because that's their default response.

Dr. Rastall, a Seattle Children's psychologist, urges parents to understand what is driving the behavior to better understand how to resolve it. It could be that the person wants to communicate, avoid a task, get attention, get something they want, or help process a situation they find uncomfortable.

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Lack of fear toward danger

This particular symptom can be frightening for loved ones, and also be a bit confusing. How can someone with ASD experience heightened anxiety and terror from something as harmless as a butterfly, yet have no fear of running right into traffic?

It's likely due to where their focus lies and their awareness of their surroundings. The sound and sudden movement of a butterfly flapping its wings nearby may pull an autistic person's focus immediately if they have a heightened sensitivity to sound and sudden movement. Conversely, the whizzing of cars going by may be drowned out by an autistic individual's focus on getting to a specific point.

Moving toward danger can also be triggered by a reaction to stimuli. For example, if an autistic child was startled and overwhelmed by a butterfly, he may start running away and simply not stop, because his only focus is getting away.

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Contradictory sensory issues

People with ASD can be hypersensitive or under-sensitive to specific stimuli, and when it comes to pain tolerance, the spectrum is, again, wide, and at times, seemingly contradictory.

For example, some may have an insensitivity to pain while also having high sensitivity to certain noises. This may be due to lack of body awareness paired with an ability to intensely focus on one thing. That kind of focus can make something like sudden pain from a burn or cut barely noticeable, while they may have a much lower threshold for other sensory stimuli like harsh sounds.

However, some people with ASD may have a very low pain tolerance. In one study, researchers looked at the brains of patients anticipating and experiencing pain in an MRI machine, and the results confirmed their hypothesis that the participants were hypersensitive to pain.

It also may be that people with autism feel pain more strongly, but have difficulty communicating it, so it presents as if they feel no pain.

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Intense compassion and empathy

One theory about autism is called the "Intense World Theory." It hypothesizes that people on the spectrum aren't deficient in empathy, but rather, they experience so much empathy and compassion that they have to shut down to deal with it or avoid it. People with autism live in a world that is constantly bombarding them with sensory input and they are too overwhelmed to parse the information coming at them or understand the patterns they see.

However, this theory has had little support in terms of research. To learn more about this, check out our article here.

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Better connection to animals than people

Many people on the spectrum are able to bond very easily with pets and other animals. They may be able to interact more easily with animals because there are less social norms and niceties to be aware of, and animals generally provide unconditional love. This could also support the intense world theory, since individuals with ASD may withdraw from social situations because of too much empathy -- something they don't have to worry about with animals.

Temple Grandin proposes that her own connection to animals was easier because she thinks in pictures. This eliminated any language barrier between her and animals.

Another reason why people with autism may bond easier with animals than people is that they tend to see the detail rather than the big picture -- so they may pick up on small cues from animals that allow them to understand them better.

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Lack of personal space

Knowing how close to stand to another person or if it's acceptable to touch them is a social skill, something those with ASD may struggle with. Not understanding common social cues (as well as not being aware of their own body movements and place in space) can mean a person with ASD invades another person's space without realizing that it is not socially acceptable or that the person is uncomfortable.

Additionally, some people with ASD may engage in socially inappropriate physical behavior with others, such as standing very close to, touching, or hugging strangers, because they need sensory stimulation or deep pressure.

Lack of personal space can be especially concerning if an autistic person is approached by someone else and is not able to distinguish between a welcome touch or an inappropriate one.

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Lack of impulse control

A lack of impulse control in an autistic individual can be triggered by a variety of things: certain foods, caffeine, sensitivities to lights and sounds, a new person or item in their vicinity, or a need to partake in a repetitive pattern (i.e., if they see buttons, they must push every single one).

This lack of control can lead to behavioral issues at home, school, or work, and monopolize the attention of those around them. And having their impulses thwarted could end up causing meltdowns or shutdowns.

Impulsivity is also a sign of ADHD, which is commonly diagnosed alongside autism. To learn more about these two comorbid disorders, check out our article here.

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Gastrointestinal problems

Many people on the spectrum have stomach problems. Researchers aren't sure whether this is a cause or symptom of the disorder, but the comorbidity is common -- about 45% of people on the spectrum experience it. Constipation, diarrhea, stomach aches, food allergies, and intense sensitivities to the texture, smell, or taste of certain foods can all point to gastrointestinal problems. Many people with autism have very selective food preferences; sometimes these sensitivities improve with age and sometimes not.

One study found that gastrointestinal issues could be caused by stress. The individuals in the study with gastrointestinal problems were given a stress test, and experienced a sharp increase in the stress hormone cortisol during it. Stress can wreak havoc on the digestive system. Learn more in our article here.

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Odd or unnatural posture

Many children with ASD engage in movements that may seem strange, and an odd posture or gait is commonly noted. This may be due to differences in the inner ear and vestibular system; because those with autism have difficulty orienting themselves, they may actually be afraid of movement and therefore engage in strange postures to compensate for that. Or, they may overcompensate by spinning around or engaging in other intense movement to purposefully alter their vestibular system.

Other odd movements an autistic individual may engage in include:

Dyspraxia: This is a comorbid disorder that can affect gross and/or fine motor skills. Learn more in our article here.

Stimming: Short for self-stimulatory behavior, this is a set of repetitive movements or sounds that people with ASD (and neurotypicals) may engage in to help calm themselves down, express themselves, or process something. Learn more in our article here.

Toe-walking: This refers to a person's preference to walk on their toes or on the balls of their feet as opposed to using the entire foot. Learn more in our article here.

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