For your consideration, a psychology study as summarized by The Economist in "How dead is dead? Sometimes, those who have died seem more alive than those who have not":
"They first asked 201 people stopped in public in New York and New England to answer questions after reading one of three short stories. In all three, a man called David was involved in a car accident and suffered serious injuries. In one, he recovered fully. In another, he died. In the third, his entire brain was destroyed except for one part that kept him breathing. Although he was technically alive, he would never again wake up.
...each participant was asked to rate David’s mental capacities, including whether he could influence the outcome of events, know right from wrong, remember incidents from his life, be aware of his environment, possess a personality and have emotions. Participants used a seven-point scale to make these ratings, where 3 indicated that they strongly agreed that he could do such things...and -3 indicated that they strongly disagreed.
...the fully recovered David rated an average of +1.77 and the dead David -0.29. That score for the dead David was surprising enough, suggesting as it did a considerable amount of mental acuity in the dead. What was extraordinary, though, was the result for the vegetative David: -1.73. In the view of the average New Yorker or New Englander, the vegetative David was more dead [-1.73] than the version who was dead [-0.29].
...they ran a follow-up experiment which had two different descriptions of the dead David. One said he had simply passed away. The other directed the participant’s attention to the corpse. It read, “After being embalmed at the morgue, he was buried in the local cemetery. David now lies in a coffin underground.”...In this follow-up study participants were also asked to rate how religious they were.
Once again, the vegetative David was seen to have less mind than the David who had “passed away”. This was equally true, regardless of how religious a participant said he was. However, ratings of the dead David’s mind in the story in which his corpse was embalmed and buried varied with the participant’s religiosity. Irreligious participants gave the buried corpse about the same mental ratings as the vegetative patient (-1.51 and -1.64 respectively). Religious participants, however, continued to ascribe less mind to the irretrievably unconscious David than they did to his buried corpse (-1.57 and 0.59).
That those who believe in an afterlife ascribe mental acuity to the dead is hardly surprising. That those who do not are inclined to do so unless heavily prompted not to is curious indeed."
Patients in persistent vegetative state (PVS) may be biologically alive, but these experiments indicate that people see PVS as a state curiously more dead than dead. Experiment 1 found that PVS patients were perceived to have less mental capacity than the dead. Experiment 2 explained this effect as an outgrowth of afterlife beliefs, and the tendency to focus on the bodies of PVS patients at the expense of their minds. Experiment 3 found that PVS is also perceived as “worse” than death: people deem early death better than being in PVS. These studies suggest that people perceive the minds of PVS patients as less valuable than those of the dead – ironically, this effect is especially robust for those high in religiosity.
Ed Yong points to another interesting study, the 2004 "The natural emergence of reasoning about the afterlife as a developmental regularity":
Participants were interviewed about the biological and psychological functioning of a dead agent. In Experiment 1, even 4- to 6-year-olds stated that biological processes ceased at death, although this trend was more apparent among 6- to 8-year-olds. In Experiment 2, 4- to 12-year-olds were asked about psychological functioning. The youngest children were equally likely to state that both cognitive and psychobiological states continued at death, whereas the oldest children were more likely to state that cognitive states continued. In Experiment 3, children and adults were asked about an array of psychological states. With the exception of preschoolers, who did not differentiate most of the psychological states, older children and adults were likely to attribute epistemic, emotional, and desire states to dead agents. These findings suggest that developmental mechanisms underlie intuitive accounts of dead agents' minds