Psychologists agree that some childhood development issues can arrest the usual pathways to forming childhood friendships. It seems to be that getting people to be our friends takes skill which means it needs to be practised. As such, some conditions will mean that these skills take longer to acquire or may never fully develop at all. People with attention deficit or hyperactivity disorders will frequently fall into this category, as will some individuals who are on the autism range of disorders. Autism spectrum disorder tends to make picking up on social norms and cues trickier, which is why it is thought to impact on how many friends someone with such a disorder will have. Equally, some people with Down's syndrome also find making friends tougher than the general population. This is something that is often put down to the later language acquisition that is noted with this condition, but there are competing theories as to why it may be the case.