1. A computerized method of analyzing a sensory-input field containing three or more distinct classes of objects, said method comprising: representing the field as a 2-dimensional array of elements in which (a) each element represents a portion of a single object in the field, (b) all of the elements representing the same class of objects are assigned a single classification value, and (c) each of the three or more classes of objects in the field is assigned a different classification value, scanning each individual element in the array systematically with a 2.times.2 window containing the element being scanned and three adjacent and connected window elements, where each of the adjacent window elements has been previously assigned an object label which uniquely identifies an object containing such adjacent element, determining the classification value of each individual element being scanned, matching the classification values in the 2.times.2 scanning window with one of fifteen same/not-same case patterns which indicates which of the elements in the window have the same classification values, and which have unique values, irrespective of actual classification values, from the same/not-same case pattern associated with the 2.times.2 window, assigning the element being scanned an existing object label or a new object label, storing the object labels determined for each of the scanned elements, and by said scanning and assigning, identifying each separate object in the field by a separate object label.