Reply to Murray Parkes

 

I should like to comment on Parkes' interesting observations on his cat,  and also on the question of why (in the ultimate, evolutionary sense)  people get depressed after the death of a baby.

   The cat who withdraws and refuses offers of nurturance after punishment  or defeat is a reasonable candidate for the role of animal model of human  depression - research on the cat brain has elucidated some of the  mechanisms of human sleep, why should it not do the same for depression?   Is the reaction of Parkes' cat typical of the species?  Is there any  literature on this?

   Is the cat adopting the metaphor of the sick role to express its  depression?  Possibly to competing cats (with whom it interacts in the  agonic mode) it is giving a message such as "I am out of action, and  therefore not likely to invade your territory, but I will defend to the  death this corner of my home territory in which I am cowering."  This is  ritual submission combined with the threat of unritualised "defence of the  nest" aggression. To the home team of the Parkes family (with whom it  interacts in the hedonic mode) it is clearly not using the sick role to  obtain nurturance, which in fact it refuses. But it could be saying, "I am  sick, therefore do not force me out into the competitive arena of life to  fight on your behalf. In particular, do not take me to a cat show, I am  not up to it."  With this message the cat may be transmitting the "off  games, out of action" (as opposed to the nurturance-eliciting) component of  the sick role signal.

   It is interesting that the depressed cat does not give invitations to  aggressive play. This may be due to two separate mechanisms. Firstly, all  the activities of the hedonic mode are inhibited in depression, so that  play is inhibited along with exploration, curiosity, affiliation, etc. Secondly, the threat and attack components of agonic interaction are 

inhibited in depression, leaving only the escape and submission components  active. Aggressive play contains the play element of hedonic interaction  and the attack element of agonic interaction, and so may be inhibited on  both counts.

   The death of a baby does not cause a fall of status or RHP, so why (in  the ultimate sense) does it sometimes cause depression (over and above  grief) in the parents?  The reality of depressive illness after the death  of a baby is beyond doubt. Recently it was brought home to me vividly by a  patient who was so incapacitated by the death of one of her twins that she  was quite unable to care for the surviving twin. That is difficult to  account for in adaptationist terms. Do we know the incidence of depression  following the death of a baby in societies in which death of a baby is a  common occurrence?  Probably the sequence "death - grief - depression" is  not sufficiently fine-grained to distinguish between the death of a  powerful ally and the death of a baby. Evolution could have produced two  different kinds of grief: one following death of an ally which could  trigger depression, and one following death of a baby or other dependant  which could not trigger depression;  but it has not done so, and all grief- induced depression is probably not adaptive.

   In terms of RHP, the yielding hypothesis of depression states that  depression is caused by loss of RHP, and the depression itself leads to  further loss of RHP, like the devaluation of a currency. Depression  following bereavement is a problem for both these propositions. Firstly,  as discussed above, the bereavement does not always lead to loss of RHP;   secondly, it has been thought since Freud's Mourning and Melancholia that  depression following bereavent (mourning) is not associated with lowered 

self-esteem (including, presumably, the RHP component of self-esteem). Is  this still thought to be true?  Has there been measurement of self-esteem  in depressions following bereavement compared to other depressions?  Or can  we say that whereas there is no loss of self-esteem during grief, when  grief triggers depression loss of self-esteem does occur?

   In general, grief is one of the dysphoric emotions which seem to have  evolved as part of the causal chain between stimulus and depressed state,  others being shame, guilt, anxiety, depressed mood (short of depressed  state), disappointment, mental and physical pain, loss of face and the  sense of being insulted or put down. These emotions are the subjective  correlates of intervening processes between stimulus and mood change. I  think what they have in common is the fact that the stimuli or conditions  which cause them are sufficiently often associated with loss of RHP that it  has been advantageous for them to cause the internal reduction of RHP which  seems to be the crucial functional element of depression. Instead of  having:

 

Insult 

            loss of RHP          depressed state 

Death

 

we have:

 

Insult      humiliation

                                 depressed state

Death       grief

 

in which humiliation is the subjective correlate of being put down, and  grief is the subjective correlate of loss of a loved one. Humiliation and  grief share with other dysphoric emotions the capacity for triggering  depression. The only difference is that whereas humiliation is always  associated with loss of RHP, grief only sometimes is. This second model is  less simple and satisfying than the first;  but the only alternative that I  can see is to postulate that the depressed state following loss is an  entirely separate condition not involving changes in RHP.

   Finally, Parkes says that nurturance of the sick is unlikely to be an innate human characteristic. There is a lot of variation, but to my  knowledge genetic studies have not attempted to analyse it. Are more MZ  than DZ twins concordant for nursing?  I do not think that other primates  nurture the sick. In The Chimpanzees of Gombe, Jane Goodall describes  chimpanzees avoiding and throwing stones at disabled conspecifics, treating  the physically ill rather as some humans treat the mentally ill. However,  "Cape hunting dogs....will even take care of the sick and injured animals  for long periods of time" (1, p46, quoting 2). Perhaps this is because (in  the ultimate sense) they share with us hunting, or having a home, or living  on the ground;  hunting, because injuries in the hunt would be too costly  if the injured were not cared for, having a home and living on the ground  because otherwise caring for the sick might just not be practicable.

 

1. Van Hoof, J.A.R.A.M. (1990) Intergroup competition and conflict in  animals and man. In: J. Van der Dennen & V. Falger (eds) Sociobiology and  Conflict: Evolutionary Perspectives on Competition, Cooperation, Violence  and Warfare. London: Chapman & Hall, Pp 23-54.

 

2. Lawick, H. van & Lawick-Goodall, J. van (1971) Innocent Killers. Boston: Houghton Mifflin.