In season 7’s midseason finale, Alicia (Alycia Debnam-Carey) outlined a theory that her fellow survivors – and the viewers – have had trouble believing. She thinks that zombies retain "" of who they were before within their minds. For most of the episode, Alicia spent her time following a zombified Senator Elias Vazquez, convinced that the walker was the . Alicia told Morgan (Lennie James) that she had come to the conclusion that zombies somehow retain their human memories.
Morgan quickly rejected this because he saw first-hand what happened to his family, and especially his son who he wanted to save even after he turned. However, this theory served as the basis of Alicia’s mission in the episode, as it was her opinion that since Senator Vazquez supposedly knew where PADRE was, his zombie would be able to take her to it. Much to her disappointment, Alicia’s plan was ultimately a failure. Instead of taking her where she wanted to go, the senator’s zombie led her straight to Strand’s tower.
Alicia not getting the results she hoped for in was a development that was easy to see coming. Most agreed with Morgan’s viewpoint. However, it’s worth noting there have been various moments in that supported her ideas. In fact, evidence for her theory dates all the way . The franchise’s first zombie – a child – was walking down the street until her gaze fell on a stuffed rabbit. Strangely, she bent down and picked it up. There is no real reason for the zombie to do this – unless Alicia is actually right about how a zombie's brain works.
As mindless, undead creatures whose only impulse is to feed on meat, it doesn’t make sense for a zombie to interact with an inanimate object or express any sense of curiosity in the slightest. The zombie picking up the stuffed rabbit is indicative of the walker displaying child-like traits or acting on a memory from the person’s past. Regardless, either explanation doesn’t fit with established mythology and rules. Though some characters in shows have struggled to come to terms with this on occasion, experience has taught most of them that a person dies completely when they turn.
Another person who believed there was something still running in the brains of the walkers was Hershel. and kept feeding her, and she was nowhere near as aggressive as other walkers. There is also an explanation here that goes beyond retaining remnants of her past life. Most walkers are desperate for something - they want to feed. Hershel was feeding Sophia, so she was less vicious than other walkers. She still attacked, but her lack of aggression might be geared toward her lack of need for sustenance since Hershel kept her fed. The same could be said for Michonne's friends when she first showed up.
There are also the variant walkers that showed up in season 11. While most walkers just lumber around slowly and grab at people to start eating them, seemed more intelligent. They could do things like pick up rocks to use as weapons. This was something not really seen since the first season and the little girl with the doll. That was also the season when Morgan's wife tried to open the front door of her house, something that required some sort of memory, helping Alicia's theory.
