Two of the biggest toy makers in history are making changes to their product lines. Mattel, maker of the Barbie doll, is adding curvy, petite and tall dolls to try to address an issue it may have connecting with young girls. LEGO is introducing a mini figure that uses a wheelchair. Rebecca Hains, professor of advertising and media studies at Salem State University in Massachusetts, and Wharton marketing professor Americus Reed recently appeared on the Knowledge at Wharton show on Wharton Business Radio on SiriusXM channel 111 to discuss the strategy behind these new product lines and what it could mean for the companies. An edited transcript of the conversation appears below. Knowledge at Wharton: Why hasn’t this kind of toy development happened before? Rebecca Hains: I think we’re at a really interesting cultural point in which social media has given consumers such a strong voice that they are being heard by brands and decision makers in a way that is really unprecedented.…