Among the more specific claims in contemplative literature are descriptions of states of deep concentration, reached through sustained practice, with defined characteristics and a defined sequence.
These have recently attracted attention outside the traditions, including some scientific investigation. It's worth separating what the sources describe from what has been examined.
What the texts describe
The classical accounts describe a series of absorption states, entered in order, each characterised by the presence or absence of particular factors.
The first is described as involving applied and sustained attention on an object, together with rapture and pleasure, and a unification of mind.
In the second, the effortful direction of attention drops away, leaving rapture, pleasure and unification.
In the third, rapture subsides, leaving a more refined pleasure alongside equanimity and clear awareness.
In the fourth, pleasure and pain both cease, leaving equanimity and a purified attention.
Beyond these, the texts describe further states characterised by increasingly abstract objects, which are described in terms that are difficult to convey outside the practice.
The descriptions are notably specific. They list which factors are present at each stage, describe the transitions, and specify what causes a practitioner to fall out of a state.
What the traditions say about reaching them
Consistently, that it requires substantial preparation.
Ethical conduct is treated as a precondition, on the practical grounds that a mind troubled by its own behaviour will not settle. This is stated repeatedly and is generally omitted from modern accounts.
Sustained practice with a single object, over extended periods, typically in retreat conditions with reduced external input.
And guidance from a teacher who has reached the states themselves, since the descriptions are difficult to apply without someone to confirm what is happening.
The traditions also differ among themselves about how deep the absorption must be to count, which is a live disagreement between contemporary teaching lineages and produces some confusion.
What has been studied
A small body of research exists, mostly involving experienced practitioners in laboratory settings.
Studies using brain imaging and physiological measurement with advanced practitioners have reported distinctive patterns during these states, differing from ordinary rest and from other meditative conditions.
Some findings suggest changes in networks associated with self-referential processing, and in measures of attention and arousal.
The limitations are substantial. Sample sizes are very small, because the population of practitioners who can reliably enter these states is small. Practitioners are self-selected and highly trained. And verification depends on self-report, since there is no external test of whether somebody has entered a particular state.
Which means the research demonstrates that something distinctive is happening physiologically, and cannot yet establish much about what.
The pleasure question
An aspect that has attracted particular interest, and warrants care.
The states are described as intensely pleasurable, in terms that practitioners frequently say exceed ordinary experience.
That description has produced interest from people seeking the experience for its own sake, which the traditions explicitly warn against.
The classical position is that these states are instrumental. They are a stabilised condition of mind in which insight practice becomes possible, and attachment to them is identified as an obstacle rather than an achievement.
Texts are quite direct about this, warning that practitioners can become attached to absorption and cease to progress.
Which is worth knowing for anybody encountering the material through contemporary channels where the pleasurable aspect is emphasised.
The accessibility debate
A live disagreement among contemporary teachers.
One position holds that these states require years of dedicated practice and retreat conditions, and that claims of rapid access describe something shallower.
Another holds that they are considerably more accessible than traditionally presented, and that intensive retreats of a week or two can produce genuine access for many practitioners.
Both positions are held by experienced teachers, which suggests the disagreement is partly about definition — how deep an absorption must be to warrant the term.
That definitional problem also affects the research, since studies depend on practitioners' own assessment of which state they entered.
The cautions
Intensive concentration practice is not risk-free, and the traditions include warnings.
Extended retreat practice can produce difficult psychological experiences, and accounts of these exist both in traditional literature and in contemporary reporting.
Practitioners with a history of psychiatric difficulty are generally advised to approach intensive practice with caution and with guidance.
And the general point about teachers applies with particular force here. These are states the traditions considered to require supervision, and the reasons for that are practical rather than merely institutional.
Why it's interesting
Regardless of what one concludes, the material has an unusual property.
Contemplative traditions frequently describe experiences in terms too vague to be examined. These descriptions are specific — they name factors, specify a sequence, describe transitions, and make claims that could in principle be investigated.
Which makes them one of the few areas where traditional contemplative claims and empirical investigation can meet on something more than mutual incomprehension.
That the research so far is thin reflects the difficulty of studying a rare capacity in a small population rather than any absence of something to study.
General information only. Anyone with a history of mental health difficulty should seek advice before undertaking intensive meditation practice.