Those complex sets are great for stimulating certain types of spatial reasoning, perseverance, and fine motor skills. My four year old went from 'building a tra

Those complex sets are great for stimulating certain types of spatial reasoning, perseverance, and fine motor skills. My four year old went from 'building a tractor (60287) with dad helping' to 'building 5+ kits all by himself'. The kits don't stop him from just building his own stuff either. The two forms of play seem complimentary.