Hair grows faster on the sides and slower on the top of your head. This might be as basic as keeping track of your sleeping habits. Because of the pressure on the scalp, whatever side you sleep on will have a greater blood flow. This will help the hair on that side grow faster. Some people claim they can tell which way their hair grew by looking at it in the mirror. If some of it grew out sideways then it's likely to grow out that way too. This is because the direction the hair grows gives us information about how our head is shaped. If most of it grew out one way but a little bit another, this means your head is not exactly symmetrical. Other things such as genetics and health conditions may also play a role in how fast or slow certain areas of the head grow. The hair on top of the head tends to grow slower because there's less blood flow up here. The skin gets thicker so more oxygen needs to diffuse into the skin to reach the hair follicles. This takes time so growth is slower than on the sides of the head. People with oily skin tend to have faster growing hair on their heads because oil helps hair grow. This is because oil makes your hair feel softer and therefore goes further when you wash it.