Where does specificity collide?

In diagnostic testing, specificity is the proportion of people who truly do not have a condition that a test correctly labels as negative: it is the true negative rate. It sits opposite sensitivity, which is the true positive rate, and the two are read together from the same confusion matrix of true and false positives and negatives. Altman and Bland's 1994 note Diagnostic tests 1: sensitivity and specificity defined the pair and warned that neither number alone tells you how useful a test is. A test can look excellent on one measure while failing badly on the other, and moving the decision threshold trades one against the other, which is what a ROC curve traces. This is a property of a classifier scored against a known truth, not of a molecule, a memory, or a word.[1]

Unit

Proportion of true negatives correctly identified, from 0 to 1

Recovery means

Not applicable

Measured by

Computed as true negatives divided by all who are truly negative, using a test scored against a gold standard, and plotted with sensitivity as a ROC curve

In immunology and biochemistry, specificity is how selectively a molecule or an immune response acts on one particular target rather than others: an enzyme acting on its substrate, or an antibody binding its antigen. The selectivity comes from complementary shape and chemistry between the two partners, so a small change in the target can sharply reduce binding. Koshland's 1958 paper Application of a theory of enzyme specificity to protein synthesis argued that the enzyme is not a rigid lock but changes shape as the substrate binds, an induced fit that helps explain why some substrates react and closely related ones do not. Here specificity is a physical property of molecular recognition, measured by how much a binder prefers one target over another. It is unrelated to a test score, a memory cue, or the reading of a noun phrase.[2]

Unit

Relative preference of a molecule for one target over others

Recovery means

Not applicable

Measured by

Assessed by binding and kinetic assays that compare activity or affinity across the intended target and near relatives, such as cross-reactivity panels

In the psychology of memory, encoding specificity is the principle that a cue helps you recall something best when it matches the way that thing was encoded at the time you learned it. What was stored, and the conditions under which it was stored, set which cues will later work. Tulving and Thomson's 1973 paper Encoding specificity and retrieval processes in episodic memory showed that a cue strongly associated with a word could still fail to prompt recall if it did not match how the word was originally studied. The claim is about the fit between encoding and retrieval, not about how selective a symptom is for a disorder, which is a separate clinical use of the same word. This is a property of remembering, not of a test, a molecule, or a phrase.[3]

Unit

Degree of match between retrieval cue and original encoding

Recovery means

Not applicable

Measured by

Studied in recall experiments that vary whether cues present at retrieval matched those present at encoding, comparing recall rates across conditions

In linguistics, specificity is a property of noun phrases that separates two readings of an indefinite: whether the speaker has a particular thing in mind or not. The sentence I am looking for a book can mean one particular book the speaker wants, the specific reading, or any book at all, the non-specific reading, and the words alone do not settle which. Fodor and Sag's 1982 paper Referential and quantificational indefinites argued that an indefinite like a book can behave either as a referring expression pointing at one thing or as a quantifier ranging over many, capturing this split. Specificity here is about reference and meaning in a sentence, marked in some languages by grammar and left ambiguous in others. It has nothing to do with a true negative rate, molecular binding, or a memory cue.[4]

Unit

Whether a noun phrase picks out a particular referent or not

Recovery means

Not applicable

Measured by

Diagnosed through scope tests and interpretation judgments that show whether an indefinite refers to one intended thing or ranges over any, sometimes marked by grammatical means