Before coronal consonants, this produced Alderney, alter, bald, balderdash, bold, cold, false, falter, fold, gold, halt, hold, malt, molten, mould/mold, old, palsy, salt, shoulder (earlier sholder), smolder, told, Wald, Walter and wold (in the sense of "tract of land").
In 2012, a researcher from the University of Nebraska at Kearney published a study reviewing research that had been done using the songbird as a model for autism spectrum disorders, noting that the neurobiology of vocalization is similar between humans and songbirds, and that, in both species, social learning plays a central role in the development of the ability to vocalize.