How did the rats learn to read in rats of nimth?

In "Rats of NIMH," the rats learned to read as a result of their exposure to an experimental environment where they were subjected to enhanced intelligence through genetic modification and environmental enrichment. The protagonist, Nicodemus, and his fellow rats acquired this ability by observing humans and engaging with written materials, demonstrating a remarkable capacity for learning and adaptation. Their newfound intelligence allowed them to develop complex societies and navigate challenges that they faced in the wild.