Mayim Bialik, PhD, (starting since mid-season 4) – a woman selected by an online dating site as Sheldon's perfect mate after Raj and Howard secretly set up an account using Sheldon's information, prompting Raj to comment, "We finally have proof that aliens walk among us!"Amy is from Glendale and is a fan of Little House on the Prairie. She and Sheldon initially have many similar traits, though after befriending Penny and Bernadette, Amy eventually becomes more interested in social and romantic interaction and is more socially aware than Sheldon. Once she and Sheldon meet, she becomes, as Sheldon puts it, a girl who is his friend, but not his "girlfriend". Their relationship slowly progresses up to the point where Sheldon considers her his girlfriend and tells her that he loves her. Amy's sexual frustration in her relationship with Sheldon is a recurring topic in the series. Amy also believes she and Penny are best friends ("besties", as she puts it), a sentiment that Penny does not share. Penny eventually becomes a real friend, overlooking Amy's Sheldon-like qualities. Amy's admiration for Penny has at times bordered on physical attraction. Amy has a PhD in neurobiology, and frequently uses monkeys in her research and experiments. Amy decides to break up with Sheldon in the season 8 finale, becoming increasingly frustrated with his quirks. Bialik herself has a doctorate in neuroscience.