Are you worried if your son or daughter line up toy? For instance, your son may line up his truck or cars, sometimes it is normal for kids to line up toy but the abnormal thing is that if your son or daughter thrown severe tantrums when the order of the toys being change.
Lining up toys or other object can be considered one symptoms of Autism Spectrum Disorder (ASD). Children with autism play with toys in unusual way such as lining up cars or trucks and getting upset when there is a disruption in the order or alignment of the line of the toys. It is alright for the kid to line up toys but throws a tantrum when one car or truck out of order or move toys from one place to another should be intervene.
Also, Lining up toys or object can be considered as symptoms of obsessive compulsive disorder. Obsessive compulsive disorder (OCD) is a disorder of the brain that greatly affects the behavior and causes anxiety for those are affected. Individual with OCD experience obsession that upset them.
For autistic children, lining up toys may provide them with comfort and sense of control in the world because for them the world is difficult to understand and navigate. Also, it is a way to control their environment.