The cognitive response to grief can be as varied as the Emotional and Physical responses covered earlier.
Initially, the cognitive response is disbelief. I'm not talking about denial, although that can occur if the disbelief persists. But the flat-out rejection of the horrific news is typically the first cognitive defense against grief, especially if the news is sudden. The grieving person believes the death absolutely could not have happened--did not happen. Usually accompanied by shakes of the head and repetitive "no's" even as his or her mind assimilates the new, life-changing information.
Denial in the most severe form can be the person going about their life as if the person never died. This is rare, though, and usually the bereaved exhibits signs of denial like inability to make decisions about a casket or funeral service. Their mind just hasn't yet fully grasped the idea that the loved one is gone, so they will put off even thinking about it at times by distracting themselves with senseless activities.
The mind might want to dwell on particular intrusive thoughts about how the deceased died, or what they were going through/feeling right before they breathed their last. This preoccupation isn't unhealthy in and of itself, but if not tempered with other positive thoughts of the deceased, it could easily slip into a morbid fascination. Other normal cognitive responses are confusion and difficulty organizing thoughts. A bereaved person might have a much harder time making themselves understood.
Maybe the more interesting aspects for writers of the grieving mind would be how the mind can play tricks on us. It's not unheard of for a grieving person to have a sense of the presence of the deceased. It doesn't have to be that they actually think the deceased is still living, and it doesn't have to be some inherently spiritual idea that the soul hasn't gone to heaven because of "unfinished business." (Think Patrick Swayze in Ghost.)
The grieving person might have auditory or visual hallucinations, which is still a cognitive response because it's origin is in the brain. It doesn't mean they are crazy, although they might think that they are. (For an example of this, read Bonnie Grove's Talking to the Dead.) On the other hand, the bereaved might find a strange sort of comfort from this after-death connection, and assign "spiritual or metaphysical explanation to the phenomena, which can help the bereaved to cope with the loss" (Worden, 1991).
Next week, we'll conclude the facets of grief series with a post about the behavioral response associated with grief. Hope to see you tomorrow for the weekly free association chain we do here on Fridays!