i6ia 



HANDBOOK OF PHYSIOLOGY 



NEUROPHYSIOLOGY III 



matches, and after it has eaten a spider, it begins 

 picking up the moss. 



In ethology, the systematic study of species-specific 

 behavior [cf. Tinbergen (486)], attempts are made to 

 assess internal states or "moods' in animals by survey- 

 ing the range of equivalent reactions to varied 

 dummies as stimuli (Attrappenversuche). Thus, mobbing 

 reactions in small birds can be elicited by balls of 

 feathers on a stick. The resulting observations are 

 sometimes interpreted as if they suggested the exist- 

 ence of particular schemata or kernel perceptions 

 which act as releasers of particular behavior sequences 

 [IRM, "innate releasing mechanisms'], for example 

 those of courtship, especially in birds [see Huxley 

 (232)] or of predator recognition (486). There is con- 

 troversy about the generality of some of the observa- 

 tions [cf. HirschW al. (216) and Tinbergen (487)], and 

 particularly about the innateness of the reactions. 

 The most radical claim in this respect is implied in 

 other recent descriptions of bird orientation. For the 

 warbler, a night migrator, Sauer (412) has reported 

 accurate orienting reactions to stellar constellations 

 (including the artificial constellations in a plane- 

 tarium), and this in birds which had been reared in 

 isolation and without any previous exposure to the 

 starry skv. 



Phenomena of animal camouflage provide strong 

 indications for similarity in pattern vision among dif- 

 ferent vertebrate species [cf. Thayer & Thayer (480)]. 

 There, the principles of perceptual grouping (272, 

 537) turn into rules for concealment, as in the con- 

 struction of hidden figures (142, 164, 165). Experi- 

 mental proof for the efficacy of protective coloration, 

 or cryptic attitudes (93) is available in a few species, 

 for camouflaged insects as prey (85) and fish and birds 

 as predators (4")8, 554). The evidence suffices to 

 establish that these concealing features act at least as 

 strongly for lower vertebrates as they do for man, 

 indicating that perceptual principles involved in 

 grouping and in camouflage antedate the evolution of 

 the human nervous system. Some species differences, 

 however, might lie in the relative ease with which 

 concealment can be overcome, conceivably, lower 

 forms arc less able to override t h<-si ■ factors I >v selective 

 attention, but evidence on this point is sparse. 



This review (it pattern perception in children and 

 subhuman forms reveals the fragmentary state of our 



information. The available methods have not been 



used sufficiently to establish valid comparisons be- 

 tween species. It is often forgotten that the same 



species that can be shown to react t < > broadlv sche- 

 matic stimuli in some situation (as stressed b) the 



ethologists) can also be trained, in the laboratory, to 

 make refined perceptual distinctions. 1 " Even within a 

 given species we usually lack systematic studies de- 

 fining both the extent of equivalence (generalization) 

 and of discrimination. These limitations will become 

 still more obvious when we turn to a review of pattern 

 perception in the higher invertebrates. Does percep- 

 tion in these forms differ as much from that in the 

 vertebrates, as the differences in the nervous systems 

 of the phyla would suggest? 



higher invertebrates: cephalopods. Studies of 

 pattern vision in higher invertebrates with large 

 image-forming eyes (such as the octopus) again sug- 

 gest a rather puzzling similarity in visual organization 

 between these forms and vertebrates. Experiments in- 

 volving successive discrimination [cf. Boycott & 

 Young (57, 58)] and transfer to equivalent patterns 

 (461 ) have revealed few differences, except that an 

 octopus trained to go to an upright triangle will 

 transfer this reaction to a rotated triangle. This is not 

 found in rats (301) nor in pigeons (4881, although it 

 does appear in monkeys (3581, chimpanzees (14b) 

 and children (146). Furthermore, Sutherland (459, 

 460) showed that the octopus seems virtually incapa- 

 ble of discriminating oblique lines (\ vs. 1, even 

 though it learns promptly to tell a vertical (j) from 

 a horizontal ( — ) line. 



This specific difficulty in discriminating mirror 

 images prompted Sutherland to postulate a neural 

 scanning mechanism in the octopus, whereby shapes 

 are classified as follows. The visual impulses are led 

 into an array of cells arranged in rows and columns, 

 and the total excitation is counted separately in 

 columns and rows. Reaction to shape is then deter- 

 mined by ratios of horizontal to vertical excitation, a 

 mode of determination which would make horizontal 

 and vertical maximally discriminable, and oblique 

 lines not at all (4,1) l' 1 ' \s Sutherland himsell 



pointsout, Lashlev (301) had noted a similar tendency 

 to confuse mirror images in rats. 



Quite recently, Rudel (unpublished observation- 

 has shown that normal children below age -i\ have 



10 That these discriminations are not only the product of 

 artificial settings is indicated by the role of individual recogni- 

 tion among birds in the maintenance of pecking orders I fis- 

 turbances in the pecking order ol chicks (Leghorn fowl an 

 most readily induced by changes around the head 01 by abrupt 

 changes in body coloi If the changes are gradually introduced, 

 they have no effect see Guhl >v Ortman (174 



"The same mechanism would account lor equivalent re- 

 actions to identical shapes of different sizes, .1 1 eaction found for 

 the octopus 1 jfii 1, pigeon |88 rat |0i and monkey (1159). 



