Decelerative Perceptual Anomalies

Decelerative Perceptual Anomalies are conditions in which an observer's subjective time perception diverges measurably from the Standard Chronometric Index (SCI) while the observer's physical rate of motion, respiration, and record-keeping remains unchanged. They are the most thoroughly administered of the Tower's perceptual complaints and the least thoroughly understood. The governing procedural document is the Manual of Perceptual Hygiene, which classifies such anomalies under Schedule B and requires that every episode longer than eleven minutes be logged in a Perceptual Dilation Log countersigned by a floor warden or, in stairwells, by the next competent person ascending.

The defining ratio is the temporal dilation factor, written d, being the quotient of subjective duration by SCI duration. Anomalies below d = 1.05 are considered atmospheric and are not reported; anomalies at or above d = 1.2 fall within the assessment schedule of the Office of Perceptual Assurance, which denominates their cost to the observer in Perceptual Scrip at a rate fixed by Standard Attenuation.

Classification

The Manual recognises three grades. Grade I anomalies are confined to a single sense and typically resolve when the observer looks away, coughs, or is addressed by name. Grade II anomalies affect two or more senses consistently and require the observer to submit a Form 12(b) within the same working day. Grade III anomalies persist across changes of floor, and their suffering observers are removed to a Decelerative Perceptual Anomaly Zone until the zone warden certifies return.

The grades are not sequential in practice. The Academy of Perceptual Absences recorded in its Third Survey of Unreliable Intervals (1411) that 63 per cent of admitted Grade III cases had first presented as Grade I, while 9 per cent presented at Grade III with no prior report at all, the observers in those cases having believed the effect to be "a quality of the afternoon" (Academy of Perceptual Absences, Third Survey, fol. 208r).

Instruments and the Chronophage Candle

Field verification is by Chronophage Candle. The candle burns at a rate calibrated to the SCI; where an observer's account of elapsed time exceeds the candle's consumption by more than the tolerance of the grade, the anomaly is confirmed and the candle is retired with honours and a notation. The OMA maintains nine hundred and forty candles in active circulation and has never explained where they are made.

Observers are reminded that a candle must not be carried into a lacuna, since the absence of a perceptual field will register on the instrument as an anomaly of the candle rather than of the observer. The resulting paperwork is identical and the candle cannot be reused.

The Winter Dispute of the Fourth Recension

Scholarly disagreement on decelerative anomalies is old and, in one instance, unresolved by any means short of a Concordance. Concordance 17, Annex C, Paragraph 4 holds that an anomaly is established by the sustained testimony of two observers of good standing, the second observer need not have witnessed the same interval. The Fourth Recension of the Manual of Perceptual Hygiene (Annex C, Para. 4, amendment of 1422) holds instead that testimony is admissible only where both observers were present in the same interval and recorded it independently, on the reasoning that two witnesses to different slow afternoons have not witnessed the same slow afternoon.

"Where the interval is not shared, the anomaly is not shared, and the second witness is a witness to nothing."

— Fourth Recension, Annex C, Paragraph 4, marginal gloss

The conflict has produced a class of cases known informally among wardens as "paired silences," in which two clerks experience dilation in adjacent rooms and neither report can be entered against the other. The OMA's standing instruction, issued in the winter of 1419 and never formally withdrawn, is to enter both reports and strike neither, "pending the reconciliation of Annex C with itself."

Decelerative anomalies and perceptual paradox

Decelerative anomalies are frequently confused with Perceptual Paradoxes, and the confusion has procedural consequences. A paradox is a property of a location and is handled by Perceptual Safeguarding; a decelerative anomaly is a property of an observer and follows the observer out of the room. Where the two coincide, the OMA's practice is to treat the location as the senior party and to detain the observer only if the dilation factor continues to rise once the paradox has been sealed. Perceptual Contamination is also sometimes pleaded, generally without success, by observers who wish their logs expunged.

Auditory presentations are referred to the Auditory Anomalies register rather than to Schedule B, though the distinction is not always clear to the reporting clerk. The Report on the Acoustic Properties of Floor 331 records a case in which a bell heard at dilated rate was entered under three separate headings over two days before a warden resolved the matter by striking out the duplications and the clerk's name.

Management and the observer's obligations

The observer's obligations are few and strictly enforced. One must sit down, note the time by any means not dependent on the self, and remain in place until the interval closes or a warden arrives. One must not attempt to measure the anomaly by walking its length, a practice that has produced no useful data and several useful injuries. One must not consume Perceptual Scrip during an episode, since the Script issued against a confirmed anomaly is denominated in the anomaly's own duration and cannot be assessed until the episode has ended.

Perceptual Fade is the principal complication, occurring in roughly one episode in thirty, generally in observers who have previously spent time in a Stack of Unmoored Perspective. A fainting observer is not to be carried; the interval will follow the body and the paperwork follows the interval.