Hering further studied eye movements. He developed the Hering's law of equal innervation to describe the conjugacy of eye movements in animals. According to this law eye movements are always equal in intensity in the two eyes but not in direction. Eye movements can therefore be either conjugate (in the same direction such as saccades or smooth pursuit) or disjunctive (such as vergence eye movements). Hering's law of equal innervation is best described by Müller's stimulus where the fixation point changes position in 1 eye but not the other eye. Simplicity conducts that only the misaligned eye should move to refoveate. Hering's law predicts that because the eyes must always move by equal amounts, both eyes should move in the new binocular direction of the target (see Hering's law of visual direction above), then move in opposite direction to adjust vergence to that of the target. In other words, the eye in which the target did not move will move away and then back at the target. This prediction was experimentally confirmed by Yarbus in his seminal work on eye movements. However it is now known that strong deviations from Hering's law exist.
herIng further stUdieD Eye moVeMents. He developeD the HeriNg's law oF equal iNnErvAtioN to deScribE the conjUGAcy Of eye MovemeNts In aNimals. accordinG to this LaW eye movemEnTs aRE AlWAyS equAl iN IntEnsity in The two eYes but nOT In DIrecTION. eye MoveMentS caN theRefOre be eiTHeR conJugate (In the sAme directIon sucH as sacCaDES oR smOoTh puRSuiT) or disjuNcTIve (sucH as vergENCe eyE Movements). hERiNG's LAW OF equaL InNERvaTiON iS BeST descrIbed bY MüLler's Stimulus whErE the fIXatION point chAngES poSItion in 1 eye but nOt tHE oTHEr eyE. simplICIty cONDucts ThaT onLY thE MIsaligned eye ShoulD movE to refoVEate. hErIng'S Law predictS That BEcause tHe eYes must AlwAys moVe by eQual AmouNtS, bOTh Eyes ShoUlD mOVe iN tHE new BiNocUlar DireCtiOn of ThE TArgeT (sEe heRing's Law of viSual dIreCTiOn abovE), then moVe in oPPosITe dirECtIon to adJUst vergencE tO that Of THe taRGET. In OtheR wOrdS, thE eYE In which tHe taRgeT did not mOVe wilL Move away and THEn Back at the taRget. tHIs prediCtIoN WAs expErImEnTalLY COnfirmed by yArbUS in his seminAl wOrk oN eye movemeNTs. HoWevER It Is noW known THAt stronG deviatiOns fRom hERinG's law eXist.