Anusaya: Reaction: The Follow-on Experience
Or if not 'reaction' proper, the nature of or sort of reaction. Blindness is the anusaya, own-making is the reaction.
In [SN 4.36.6] The Buddha describes how both the common person and the Arahant undergo painful experiences, pleasant experiencess and experiences that are not painful but not pleasant. He then explains that the difference between the two is that the Arahant does not add to his pain by an emotional or 'follow-on' component.
Here I believe we have illustrated a very clear idea of what is meant by 'anusaya' (Woodward's 'lurking tendency'; Bhk. Bodhi and Nanaponika Thera: 'underlying tendency'; Bhk. Thanissaro: 'resistant obsession'.
It is simply put, the emotional (heart-felt) mental attitude that arises subsequent (following after, 'anu') to an experience. The 'follow-on' experience.
Experiencing pain the anusaya is a mental attitude of repugnance. Experiencing pleasure the anusaya is a mental attitude of attachment to plesant sense experience. Experiencing what is not unpleasant-but-not-pleasant the anusaya is blindness.
Blindness as a reaction to experiencess that are not-unpleasant-but-not-pleasant may not be seen by some as 'emotional', but this should be understood as per Websters: emotion 2a: the affective aspect of consciousness, feeling; and b: a reaction of or effect upon this aspect of consciousness. The common person reacts to this sort of experience with the desire to escape it in the experience of pleasure, hence his anusaya is blindness to the outcome.
The way this term is usually translated it has been made into a mystery. 'The Lurking Tendency'. Something remote from 'reaction'. But it is, in simple terms, the reaction and probably should be translated using this term.
Living with the eye-force controlled, beggars,
the heart is releaved from the eye's-consciousness of shapes.
As such, enjoyment is born in the releaved heart.
With joy, enthusiasm is born.
Enthusiastic in mind, the body experiences impassivity.
Impassive in body, pleasure is experienced.
A pleased heart has arrived at serenity.
Serene in heart, things become clear.
Things being clear,
you thus get a measure of living carefully.
SN 4.35.97, Olds translation
See also: SN 4.35.58 where The Buddha teaches a bhikkhu what it is that results in letting go of the Anusaya.
and: SN 4.35.59 where The Buddha teaches a bhikkhu the method for exterpating the Anusaya.
Anusaya. Previous translation suggestions: Bent, bias, proclivity, the persistance of a dormant or latent disposition, predisposition, tendency. Always in bad sense. In the oldest texts the word usually occurs absolutely, without mention of the cause or direction of the bias. EDIT: Previously I put forward the suggestion that anusaya meant the tendency of a habit to present itself time and time again for a long time following the insight into and the breaking of a bad habit. In SN 4.36.006 however we are given a very clear explanation of anusaya as being the follow-on emotional/mental component of the ordinary person's reaction to the experience of sensation.
After all this see:
A dialogue between Venerable Khema and a group of elder bhikkhus concerning identification with the five fuel stockpiles (khandhas).
This is a very instructive sutta told with a wonderful sense of humor. The very important thing to note here is Khema's explanation of how it can be that though one has thoroughly broken the idea of identification of self with the khandhas, there can remain a subtle inclination towards this identification.
"Friends, even though a noble disciple has abandoned the five lower fetters, still, in relation to the five aggregates subject to clinging, there lingers in him a residual conceit 'I am,' a desire 'I am,' an underlying tendency 'I am' that has not yet been uprooted."
There is a difference between being convinced that there is no thing there that is the self and actually seeing what is there as not-self.
Another angle to consider when pondering the meaning of 'anusaya'. This would be more of an underlying tendency than a reaction.