A POSSIBLE ANSWER UNFOLDS

X must believe Y to be to be responsible for something which violated
one of X's motives, e.g. X believes Y did something X disliked, or
that Y failed to do something X wanted done.

This is not sufficient, for X might merely regret the occurrence, or
forgive Y, and not be angry.

For X to be angry, his belief must interact with a motive-generator
to produce a new motive: he must want to do something to violate one
of Y's motives.

X's new motive need not be selected for action: it need not become an
intention, for instance because X is afraid of the consequences of
acting on it, or disapproves of vengeance.

Alternatively, execution of the intention may be postponed.

This is not yet enough. X may have the desire, but put it out of mind,
and calmly get on with something else, and in that case he would not
be angry.

Anger involves a fairly intense, desire to do something to Y: the
desire should frequently 'request attention', so it will frequently
come back into X's thoughts, making it hard for him to concentrate on
other activities.

This aspect of anger and other emotions makes essential use of
'interrupt' mechanisms which can be shown to be desirable within any
intelligent animal or robot with multiple motives in a complex and
partly unpredictable world.

For rational anger, the desire to harm Y must not be one which X would
have had in any case.

The new desired it must arise out of the belief that Y has violated
one of X's motives:

E.g. the desire to harm Y should be redirected to Z on learning that
it was Z, not Y, who was responsible.

Further, X must to some extent regard Y as a responsible agent who
intended to do what he did.

This sort of anger is possible only in animals able to represent
others as having beliefs, motives, etc., and capable of suffering.

More primitive species might merely respond with violence to violators
of their motives.

Some humans are like this.

Unconscious or irrational anger is possible too, and would require
some of the conditions to be modified.

In irrational anger X's desire to harm Y might not be linked into X's
cognitive mechanisms in such a way that it disappears when it is
discovered that Y was not the cause of the violation of X's motive.

Some of the states and processes might be conscious, others
unconscious.

In particular, even if the information about internal processes is
accessible to self-monitoring processes, the monitoring routines need
not have the descriptive resources to characterise what is happening
accurately.

Besides producing mental disturbances i.e. constantly intruding into
X's decision making, anger may also produce physical disturbances,
such as sweating, shaking, feelings of tension, tendencies to perform
violent actions, such as stamping, thumping objects.

These are sometimes related to mechanisms required for survival and
achievement of complex goals.

For instance, it is sometimes necessary suddenly to reorganise the
movements of hands, arms, legs, etc.

However, it is not necessary that anger involve any such physical
effects. If X satisfied all the other conditions he could rightly
describe himself as being angry, even very angry, despite not having
the physical symptoms.

The anger might then be described as 'cold' or 'cold-blooded'. Yet the
feeling could be strong, insofar as it constantly intruded into
thoughts and decisions, and insofar as X strongly desired to make Y
suffer, and suffer a great deal.

What does all this imply about the information processing mechanisms
in typical humans?

Which other organisms are capable of being in these states, or in
various subsets of those states?

At what stage in biological evolution did anger first become possible?

Can a fish be angry with another fish?

We can ask similar questions about many other mental states and
processes.

Can a goldfish long for its mother?

If not why not?