Question: In what year was the developer of the psychological theory "Field theory" born?
Context: In mathematics, class field theory is a major branch of algebraic number theory that studies abelian extensions of local fields (one-dimensional local fields) and "global fields" (one-dimensional global fields) such as number fields and function fields of curves over finite fields in terms of abelian topological groups associated to the fields.  It also studies various arithmetic properties of such abelian extensions.  Class field theory includes global class field theory and local class field theory. String field theory (SFT) is a formalism in string theory in which the dynamics of relativistic strings is reformulated in the language of quantum field theory.  This is accomplished at the level of perturbation theory by finding a collection of vertices for joining and splitting strings, as well as string propagators, that give a Feynman diagram-like expansion for string scattering amplitudes.  In most string field theories, this expansion is encoded by a classical action found by second-quantizing the free string and adding interaction terms.  As is usually the case in second quantization, a classical field configuration of the second-quantized theory is given by a wave function in the original theory.  In the case of string field theory, this implies that a classical configuration, usually called the string field, is given by an element of the free string Fock space. In physics, an effective field theory is a type of approximation to (or effective theory for) an underlying physical theory, such as a quantum field theory or a statistical mechanics model.  An effective field theory includes the appropriate degrees of freedom to describe physical phenomena occurring at a chosen length scale or energy scale, while ignoring substructure and degrees of freedom at shorter distances (or, equivalently, at higher energies).  Intuitively, one averages over the behavior of the underlying theory at shorter length scales to derive what is hoped to be a simplified model at longer length scales.  Effective field theories typically work best when there is a large separation between length scale of interest and the length scale of the underlying dynamics.  Effective field theories have found use in particle physics, statistical mechanics, condensed matter physics, general relativity, and hydrodynamics.  They simplify calculations, and allow treatment of dissipation and radiation effects In mathematical physics, "constructive quantum field theory" is the field whose objective is to establish existence theorems for models of quantum field theory.  Such theorems were proved in the 1960s and 1970s for quantum field theory models in two and three dimensional space-times in the papers by James Glimm, Arthur Jaffe, Irving Segal, Edward Nelson, and others.  The main goal of constructive quantum field theory, an existence proof of non-trivial quantum field theory models in a four dimensional space-time, has not been reached.  In the meantime, the theoretical physics community came to believe that the current state of the art quantum field theory models are merely effective models rather than fundamental theories, whose mathematical status is of little practical relevance, and interest in constructive quantum field theory has waned. In mathematical physics, covariant classical field theory represents classical fields by sections of fiber bundles, and their dynamics is phrased in the context of a finite-dimensional space of fields.  Nowadays, it is well known that jet bundles and the variational bicomplex are the correct domain for such a description.  The Hamiltonian variant of covariant classical field theory is the covariant Hamiltonian field theory where momenta correspond to derivatives of field variables with respect to all world coordinates.  Non-autonomous mechanics is formulated as covariant classical field theory on fiber bundles over the time axis ℝ. In mathematics, geometric class field theory is an extension of class field theory to higher-dimensional geometrical objects: much the same way as class field theory describes the abelianization of the Galois group of a local or global field, geometric class field theory describes the abelianized fundamental group of higher dimensional schemes in terms of data related to algebraic cycles. Field theory is a psychological theory (more precisely: Topological and vector psychology) which examines patterns of interaction between the individual and the total field, or environment.  The concept first made its appearance in psychology with roots to the holistic perspective of Gestalt theories.  It was developed by Kurt Lewin, a Gestalt psychologist, in the 1940s. Kurt Lewin (September 9, 1890 – February 12, 1947) was a German-American psychologist, known as one of the modern pioneers of social, organizational, and applied psychology in the United States.  Exiled from the land of his birth, Lewin ( ) made a new life for himself, in which he defined himself and his contributions within three lenses of analysis: applied research, action research, and group communication were his major offerings to the field of communication. In theoretical physics, Hamiltonian field theory is the field-theoretic analogue to classical Hamiltonian mechanics.  It is a formalism in classical field theory alongside Lagrangian field theory, and has applications in quantum field theory also. Information field theory (IFT) is a Bayesian statistical field theory relating to signal reconstruction, cosmography, and other related areas.  IFT summarize the information available on a physical field using Bayesian probabilities.  It uses computational techniques developed for quantum field theory and statistical field theory to handle the infinite number of degrees of freedom of a field and to derive algorithms for the calculation of field expectation values.  For example, the posterior expectation value of a field generated by a known Gaussian process and measured by a linear device with known Gaussian noise statistics is given by a generalized Wiener filter applied to the measured data.  IFT extends such known filter formula to situations with nonlinear devices, non-Gaussian field or noise statistics, dependence of the noise statistics on the field values, and partly unknown parameters of measurement.  For this it uses Feynman diagrams, renormalisation flow equations, and other methods from mathematical physics.
Answer: 1890