Products that contain bismuth can temporarily turn your tongue black, according to Atlas of Adult Physical Diagnosis. Other Causes If you have a black tongue, then you could have a fungus called Aspergillus niger growing on the surface of your tongue. If you have too much bacteria growing in your mouth, it could cause your tongue to appear black and hairy, according to the Mayo Clinic.
In addition, a child is said to have a cognitive delay and/or a learning disability when they are performing at least two grade levels below their peers. For example, a third grade class is learning their multiplication tables, but a student with a cognitive delay would be performing math on a first grade level.
The warning signs: 1  Your child is delayed in more than one area. For instance, she's 15 months old and hasn't uttered a word or taken a step, and she seems to be wrapped up in her own world, or she doesn't turn to look at you when you enter a room or say her name. 2  The delay is two months or more from the norm.