EXPRESIONES DE UNA CULTURA LOCAL

The o b ject (V* black square) s a t on the end of the runway, but the runway, in stead o f being coqqpletely w liite, was painted black from th e fo o t o f the ob ject to a distan ce 3' away from i t . I t was hoped thus to present the animal with a f a ls e base lin e 3" away from the ob ject, the r e a l base l in e , where the black o b jects met the black flo o r , being in v is ib le . The animals were only accounted to iiave respv ded p o s itiv e ly i f the antennae

w .

were moved before the head reached the a r t i f i c i a l base lih e . Animals which sta rted beating when the toad waa over the base lin e or beyond i t were scored as n eg ativ e,

R esu lts. The r e s u lts are s e t out in Table29 , and the average d ista n ces for the p o sitiv e responses are given.

The m ajority o f the animals responded p o s itiv e ly , showing th at the f a ls e base lin e could m l »ase antenna beating, Most of the animals continued to beat a l l th e vay from the fa ls e base lin e to the o b ject i t s e l f . Several v r ia tio n s in behaviour were observed. Thus a few animals paused before th e base lin e and in one case th e animal then moved cau tio u sly forward w itli the antm nae extended h o rizo n ta lly as i f "ex­ pecting" to tilt a v e r t ic a l o b ject. In a few other cases the animals sta rted beating before the b a se lin e , then paused about 1" p a st i t and

then approached tto o b ject with antennae beating. In most cases the

antennae vere held h o rizo n ta lly w hile beating but in a few cases they were pointed riown at the base lin e . I t seemed q u ite c lea r, however, in a l l the p o sitiv e c a ses, that the fa ls e base lin e was tto stim ulus causing the animals to beat a t such a long distan ce fro a the r e a l ver­ t i c a l o b ject.

Experiment 7 .

I f the base lin e were the only important stim ulus for r elea sin g th e antenna beating th ere was every reason to suppose th at animals walking on a black surface and confronted with a white o b ject would show^ tto response for tto black/w hite base lin e would s t i l l be d is tin c t .

Fig. 18.

Résumé of experiments 4 - 9 fo r studying antenna "beating. Diagramatic views of the v isu al situ a tio n s in these expts. as perhaps appearing to an in se ct walking along the runway. The oblique lin e s represent th e runway in p erspective.

V ertical lin e s represent the edges of v e rtic a l o b jects(th ere beîng no v e rtic a l object in expt. 9 ).

♦ in d icates th a t in th is situ a tio n antenna movements were seen. - in d icates " " " ” ^ antenna movements were seen.

81.

Accordingly t h is was done. The experim ental runs were made w ith a black runway and a w hite rectan gle 4" t a l l by 1" broad. The co n tro ls were o f two kinds ( l ) white ob ject 4” by 1" broad on a white runway and (2) black o b ject 4" by 1" on a white runway (se e Fi. • 1 8 ).

R esults. The re s u lts are presented in Table 30.

Although the nunfcer of animals te ste d was sm all, an extremely curious fa c t was at once obvious. Anl?nal« on a black flo o r confronted with a wiiite object showed no more response than to a white object on a white flo o r, in both cases walking stra ig h t in to the object with the antennae s t i l l e re c t. The sane animals showed perfectly normal responses to tto black object on a white flo o r. The lack of response in the case of white object/will te flo o r was unders Land able since the base lin e was not obvious, but there was no reason to suppose th a t the base lin e where the white O' je c t joined the black flo o r was not v is ib le to the animals. One difference which existed between the situ atio n s "black object/w hite floor" and "white obj ect/b lack floor" was tiia t, since ttie arrangement was se t up a^^ainst a white background, the widte object was not v is ib le to the

animaii, ' only i t s base lin e . Fi&.18 shows the o p tic a l situ a tio n s

diagram raatically. Up t i l l now atten tio n had been focused on the impor­ tance of the base lin e alone, but i t was extremely possible th a t the object i t s e l f played some ro le in releasin g tlie antenna beating. The very f i r s t experiments hau dismissed the actu al siz e of the object as being of any significance but the mere fa c t th a t a v e rtic a l object was v isib le to the animal might be im portant. This was tested in the next

82.

experim ent, E xperim ent 8.

U'dng & will te background and a wnite runway the animals were presented f i r s t w itli a p la in w hite o b ject (4" t a l l and 1" broad) and then witli the same o b ject w ith the add ition o f a narrow black str ip e

( l / l6" wide) on each v e r t ic a l edge.

R e su lts. The«se are given in Table 31. For the most p art the animale walked str a ig h t in to the p la in o b ject w ithout even moving the antennae from th e "erect" p o s itio n . No beating wa« ever observed, the only movement was a low ering o f both antennae to explore th e fa in t base lin e , R’hen the v e r tic a l edges o f the o b ject were picked out in black b eatin g occurred in a great many case®, dipping of th e antennae was al*o observed in ®ome case® combined with b ea tin g , the antennae p o in tin g do\'^nwards and m v in g a lte r n a te ly . '^uiie c le a r ly the v e r tic a l

edges played an im portant part in r e le a sin g antenna b eatin g. The pro-

2

p o r t io n s 14; 36 and 40:10 (T able 31) were compared by the X t e s t and

were found to d iffe r s ig n ific a n tly (P ^ .o l ) .

The importance of the base lin e had now to be re-examined indepen­ d ently o f any v e r t ic a l o b ject ( a l l p r e v io u s experim ents had included

v e r tic a l o b je c ts ).

Experiment 9.

In th is experim ent the animals were made to walk along a long runway o f which h a lf the len gth was white and h a lf black. This wa« placed

63.

were placed on one end and as they walked along to the other end U ieir behaviour was noted. They were t 's t e d botii walking from white to black and in the opp osite d ir e c tio n , AniTnals showing movements o f both

antennae a t tto black/w hite boun iary were scored p o s itiv e . R esu lts. These arn given in Table 32 ,

From them i t i s at once clea r th a t fa r more responses were obtained when the animals crossed from tlie white to tho black tlian when tra v ersin g

the opp osite path. The antenna movements a t the boundary co n sisted in

the antennae bein- brought forward and pointed down a t tiie boundary. This was c le a r ly q u ite a separate respcxise from the normal beating and the word "dipping" was used to describ e i t . In many ca ses, the in s e c ts , when walking from white to b lack, paused b r ie fly about one inch before the boundary and then moved f o r . ard again with the antennae dipping to touch the boundary or c lo se to i t .

The question whLcu had now to be answered was wly there should be more responses when the animals walked from wtdte to black than when walking; from black to w hite. Therm were two p o s s ib ilit ie s , e ith e r

( l ) the black part o f the board was more e ffe c tiv e in relea sin g the

response because i t contracted with the white background (wallsand flo o r ) or (2) the antenna movements were released hy the darkening o f the

v isu a l f i e l d wldch occurred as the animal approached the black part of the runway, but not by the brightening which occurred wtien i t crossed in the opp osite d ir e c tio n . The f in a l experiment arranged to t e s t th is was so designed as to obviate the f i r s t p o s s ib iliV ^nd to t e s t

84.

Experiment 10.

Apparatus. This was simply a white arena 2 f t , in diameter with h a lf tho flo o r made o f black card and h a lf o f wljite. The se ctio n s were la id accu rately edge to edge so th at the boundary was com pletely smooth. An anjjnal was placed in the cen tre of one sid e of the arena and a t a l l black o b ject (8" X 2") placed d iam etrica lly opposite on the other w a ll. To t h is tto animal was a ttra cted and hence was induced to cross the

black/w hite boundary at approximately r ig h t an gles. -»ince the o b ject