because their screws don't taste as good

My brother does this.. I ask him why, & he just replies "I dunno." and keeps on biting them. When he was little, we took him to the doctor because he had abdominal pains, and after a few tests, the doctor said he had started chewing fragments of thumbnail off & swallowing them, which upset his digestive system (or was it because the grime under his nails had made him sick.. I cant quite remember) so we had to find ways of making him stop. He's 18 now & still sits on his bed chewing & swalloing bits of his thumbnail though. We never could break the habit, & he's just as bad now as when he was 3. All the grime & dirt on his hands (he's a 2nd year apprentice mechanic & doesnt believe in washing his hands) will surely give him some kind of hepatitis or something I bet.

Oral fixation, and out of habit.

It is just a nervous habit.

Because they're SICK. I have a friend who bites her nails, but with her I think it's more of an insanity problem. (I love you Emily!)

because they don't let others bite their nails. now, watching loved ones biting their toe nails, that's gross.

anxiety or habit.

Nervous habit and a very difficult one to break.

It is a nervous compulsion that becomes a strong habit to break. I love Brad Pit, and I recent photo I saw shows that he bites his nails. I was surprised to see that! You'd be surprised at the number of folks (celebrities) that still do as an adult. I did until one day, as a late teenager, I decided to stop doing it. I think we had a Science class that told us how many germs were under one fingernail and that was it for me. I just stopped cold turkey. Glad I did. Nasty little habit. Beats thumb sucking! LOLO!

Nervous habit I suppose. I never understood why someone would do that. Putting an unwashed part of your hand into your mouth is very unsanitary.

Because it's what I did when I was bored in school...it entertained me somewhat (Wasn't due to my lack of paying attention..I just knew what they were saying already)

Out of habit. And because they come in 5 new flavors.

I did it when I was little because I'd get bored really easily. I stopped when I became a teenager.

Nail biting can be more than just a bad habit. It can be the result of a faulty cingulate system in the brain. Did you know that onychophagia (nail biting) is categorized as an obsessive-compulsive (OCD) spectrum disorder and can be the result of a problematic cingulate system? (The cingulate system is the part of your brain that deals with your ability to shift attention, cognitive flexibility--ability to adapt to change, deal successfully with new problems--adaptability, movement from idea to idea, ablility to see options, ability to "go with the flow", ability to cooperate--shifting attention and with getting stuck in innefective behavior patterns). In a fantastic book I read called Change Your Brain, Change Your Life by a man named Dr. Amen (a clinical neuroscientist, child and adolescent psychiatrist, and medical directer of the Amen Clinic For Behavioral Medicine), he talks about problems with the Cingulate System, which include: --Worrying --Holding onto hurts from the past --Getting stuck on thoughts (obsessions) --Getting stuck on behaviors (compulsions) --Oppositional behavior --Argumentativeness --Uncooperativeness; tendency to say no automatically --Addictive behaviors (alcohol or drug abuse, eating disorders) --Cognitive inflexibility --Road rage --“I would also add oppositional defiant disorder.”~Dr. Amen --Obsessive Compulsive Disorder (OCD) --OCD spectrum disorders: "There is a group of disorders that have been recently labeled obsessive-compulsive spectrum disorders. People with these disorders get stuck on unwanted, repetitive thoughts and cannot get them out of their minds unless they act in a specific manner. According to psychiatrist Ronald Pies, postulated OCD spectrum disorders include: Onychophagia (nail biting) Tourette's syndrom (involuntary motor and vocal tics) Kleptromania Body dysmorphic disorder (feeling that part of the body is excessively ugly) Hypochondria Autism Compulsive shopping (repetitive thoughts like 'I need to buy this one thing! I need to buy this one thing! I need to buy this one thing!') Pathological gambling Chronic pain Addictive disorders Eating disorders (such as anorexia and bulimia--in which there are "repetitive thoughts that significantly interfere with behavior" like '''Im too fat! I'm too fat! I'm too fat!' despite rational evidence to the contrary") Trichotillomania (pulling out one's own hair) If a person's nail biting is a symptom of a faulty cingulate system, an antiobsessive medication might provide relief. According to Dr. Amen (at the time of his writing, in 1998) "there are eight "antiobsessive medications" and more on the way. The current medications that have shown effectiveness with OCD [and OCD spectrum disorders I assume] are Anafranil (clomipramine), Prozac (fluoxetine), Zoloft (sertraline), Paxil (paroxetine), Effexor (venlafaxine), Serzone (nefazodone), Remeron (mirtazapine), and Luvox (fluvoxamine). These medications have provided many patients with profound relief from OCD symptoms. In addition, behavior therapy is often helpful...." I hope this information is helpful, Amy

I don't know, but I've always done it. People like me are just hard-wired to bite their nails.