Two children playing with jigsaws. Toys such as this are helpful in studying a child's cognitive and reasoning skill development. This is the ability to recognise shapes and patterns, and to use trial-and-error logic to fit the pieces together. The first jigsaws may only have six pieces with a very simple pattern using primary colours. As the cognitive and reasoning skills increase over many years, the child will be able to construct jigsaws with progressively more pieces and with more convoluted patterns and subtler colours.