tropotaxis
noun
tro·po·tax·is ˌtrō-pə-ˈtak-səs 
ˌträ-
: a taxis in which an organism orients itself by the simultaneous comparison of stimuli of different intensity acting on separate end organs
Word History
Etymology
borrowed from German Tropotaxis, from tropo- tropo- + -taxis -taxis
Note: The term was introduced by the German biologist Alfred Kühn (1885-1968) in Die Orientierung der Tiere im Raum (Jena, 1919), pp. 9-10: "In der Tropotaxis stellen sie [die meisten frei beweglichen Tiere] sich in einem Reizfelde symmetrisch ein so, dass rechte und linke Seite gleich stark von dem Reiz getroffen werden." ("In tropotaxis they [most freely motile animals] situate themselves in a stimulus field symmetrically, so that the left and right sides are affected by the stimulus with equal strength.")
First Known Use
1926, in the meaning defined above