Reply to
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.
2. Lawick, H. van
& Lawick-Goodall, J. van (1971) Innocent
Killers.