For the sake of clarity, "boneless" and its derivatives will be used in this document only in relation to things within SCP-3181, and should not be understood as synonymous with a lack of bones.

SCP-3181 prior to containment.

Item #: SCP-3181
Object Class: Safe
Special Containment Procedures: SCP-3181 has been purchased by the Foundation and its exterior remodeled such that its SEP index is 0.1, minimizing public interest.1 Remote surveillance is performed from an office building that shares SCP-3181's parking lot.
Description: SCP-3181 is a small building in the business district of ██████, Oklahoma. Within the confines of SCP-3181, the concept of "boneless" is distinct from the lack of bones: something can be boneless despite possessing bones, and the lack of bones is irrelevant to whether something is boneless. Furthermore, any object, event, location, information, etc. can be sensically described as "boneless" or "not boneless". Standard anti-cognitohazard precautions do not affect SCP-3181's anomalous property, indicating that this is not a perception-altering anomaly, but instead some other phenomenon.2 No unusual physical phenomena have been detected in or near SCP-3181.
Almost all humans possess an intuitive understanding of bonelessness while inside SCP-3181; however, they will define the term with its conventional definition (lacking in bones), despite the two properties objectively having no correlation. As a result, the actual meaning of "boneless" is unknown. Subjects experience a level of cognitive dissonance that prevents them from carrying this to its logical conclusion; for example, while a subject might identify an animal as boneless, and believe that bonelessness implies the lack of bones, they will interact with the animal as though they believe it to possess bones. Objective assessment of the situation can only be performed outside of SCP-3181, though this prevents the recognition of bonelessness.
When provided with the same information about something, 98% of subjects will agree on whether it is boneless, provided they are given enough information to make the judgment, and the thing is inside SCP-3181. Visual information alone is sufficient to identify bonelessness in 65% of cases (or 40% when color information is withheld), while a further 20% can be confirmed boneless via touch; in all remaining cases, some combination of the two is necessary.
Relatively intelligent animals can usually be classically conditioned to differentially respond to boneless stimuli. Additionally, an artificial neural network has been trained to differentiate between boneless and non-boneless images with a 71% success rate, though it will only perform better than chance while it is inside SCP-3181.
The following generalizations have been made about bonelessness:

Any two things that are mostly identical will either both be boneless or both be non-boneless. The probability of two things sharing the same bonelessness status decreases as differences accrue between them.
All non-boneless things (except for food products) have a similar boneless counterpart, which can be conceptualized and often created. The reverse is not true — several boneless things are dissimilar from all known non-boneless things.
A subject's ability to render something boneless is proportional to their will to accomplish the task, and only weakly proportional to their skill at the acts necessary to do so.
Somewhere between 10% and 40% of all things are boneless, depending on how "things" are quantified.3
Boneless things are considerably more desirable than comparable non-boneless things. Canines are unique in preferring non-boneless things.
Ordained priests of any Christian denomination are always boneless. Other humans are almost never boneless.
Things that appear angry, insufficiently clothed, or internet-connected are more likely to be boneless.
Temperature is irrelevant to bonelessness unless it results in an obvious qualitative change.
Food products are never boneless.

While other hypotheses have been made about bonelessness, the statistical methods necessary to evaluate these hypotheses have not been agreed upon; those present in this document are those that are understood as true by consensus of SCP-3181's research team, or that are considered relevant enough to include provisionally. Appendix A (Download PDF - 218.0 MB) contains a list of all things for which bonelessness status is known.
SCP-3181 developed its anomalous property in January of 2018; while unusual references to bonelessness in SCP-3181 date back to January 17, the overall low frequency of these reports suggests that the anomaly could have manifested earlier. SCP-3181 came to the Foundation's attention after SCP-3181 began to receive negative reviews in several online aggregators, with customers complaining that employees refused to serve them boneless food.
A thorough examination of SCP-3181 found no abnormalities that could account for its anomalous property. Despite SCP-3181 serving as a fried chicken restaurant immediately prior to containment, none of the garbage cans contained any bones.

Footnotes
1. In practice, objects with an SEP index of 0.5 or lower are almost never consciously noticed unless the observer has received specialized awareness training or is already interested in the object.
2. SCP-3181 has been tentatively described as a Intersemantic Complexity Zone, though this classification is not yet sufficiently well-characterized to contribute to understanding SCP-3181.
3. Notably, almost none of the physical objects present inside SCP-3181 at time of recovery were boneless.

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