Where does mirror collide?

Lacan's 1949 The Mirror Stage as Formative of the Function of the I named a developmental moment in which a young child, seeing its own reflection, identifies with that whole image before it has full motor control of its body. In this account the reflected image supplies a felt unity that the infant does not yet possess from the inside, and that identification is treated as a founding step in the formation of the ego. The referent here is a psychoanalytic claim about how the self is constituted through an outside image, not a class of neuron in the brain or a geometric partner of a manifold.[1]

Unit

One developmental episode of identification with the mirror image, described qualitatively

Recovery means

Not applicable

Measured by

Not operationalised as a metric; described through clinical and theoretical interpretation of child development

In string theory, mirror symmetry is a correspondence that pairs two geometrically different Calabi-Yau manifolds so that a string theory built on one is physically equivalent to a string theory built on the other. Lerche, Vafa, and Warner's 1989 Chiral rings in N = 2 superconformal theories first identified the algebraic structure, two distinct rings whose interchange points to such a pairing; Greene and Plesser's 1990 Duality in Calabi-Yau moduli space then constructed explicit mirror pairs, and Candelas, de la Ossa, Green, and Parkes's 1991 A pair of Calabi-Yau manifolds as an exactly soluble superconformal theory used one manifold to compute quantities on its partner. The referent is a formal duality between abstract six-dimensional shapes, not a reflection a child identifies with or a firing cell in the brain.[2][3][4]

Unit

One matched pair of Calabi-Yau manifolds related by the duality

Recovery means

Not applicable

Measured by

Established mathematically by matching Hodge numbers and physical quantities, and used to compute one manifold's invariants from the other

A mirror neuron is a nerve cell that fires both when an animal performs a particular action and when it watches another individual perform the same action. di Pellegrino, Fadiga, Fogassi, Gallese, and Rizzolatti's 1992 Understanding motor events: A neurophysiological study first reported such cells in the premotor cortex of the macaque monkey, and Rizzolatti, Fadiga, Gallese, and Fogassi's 1996 Premotor cortex and the recognition of motor actions characterised the system and gave it its name. The referent is a measured firing pattern in single brain cells, not a psychoanalytic image of the self or a geometric pairing of manifolds.[5][6]

Unit

One neuron's firing recorded during both performed and observed action

Recovery means

Not applicable

Measured by

Recorded by single-cell electrophysiology, counting spikes during executed versus observed actions