7-21; 0 Vth-

without written permission fkom ti:e pulisherr

sbacher’s account of d istorti

e assumed that ju

_.. -.. _____ _ _

is study was carried out as p rt of a project under the s hall. The author is now at Indiana niversity,

17

ide n$U periods (2333 and ter than steady illuminati

e ore sent study attempts to tesi these opposing predictions.

52 second-jxar ysychuiog~j students at ;,$I ustr~~~a. Students in this course do not re

aaive with respect to th:: SS with uncorrected visual effects were excluded from

c line 12 cm lo e of 2 1 cm fro

t line 3 cm long and 0.4 cm wide. Illumina- lobes mounted in series obes were mounted to

side of the slot, thereby preventing a direct view of the filaments

ft 1. and the center Sine was *auied tkaou

e iachonletsr shaft

st the center line t

djustmknts were made

ere made for each with the arc being

20 GORDON STANLEY

adjustment during wl:hich time E recorded for the ae.xt jpresMtt+BtiHL

East result and prc=

inz;tructed ‘to keep fixat dot in the center so see the arc-line out of hen the

shutter first opens the center line will #be less bright (brighter) th &e outside: line. You will be required to increase (decrease) the bri ness of the center line so that it matches the brightness of the outside arc-line,1 To do this you will have to turn this knob with your right

and (E places Ss hand on concealed kno incre turning to the left decreases th f&P. our adjustments as quickly as you can. satisiied. that the center line is equal in brightness to the outside arc line, please in&ate. On some occasions you may find that arc is not homogeneous in brightness i.e. one section may appear brighter than another. (A long trail often occurs in movement condi- tions.) 1In !~c;hi. eases please match to the brightest section of the arc.’

&StiLTS APJ?) THSCUSSION

Table 1 shows the group median 2 brightness adjustments made under each exp&nentaI condition (stationary olnd rotating at 30, 45, $8 and 75 rpmj for both arc luminances (63 and 100 ft IL).

in i.ntez+preting this table it should be recalled that the S adjusted the center line to the values, shown a:$ the task required was to mat

TABLE 1 Grcrug~ median brightness adjustments under eachl experimental c:ondition

srm of arc .-- -------- ---

Apparent brighitness

63 ft 1. std. 100 ft ‘I. std. Stationiary ................. 100 ft 1. 126 k 1.

rprrl .................. 316 ft 1. 447 ft 1. I-pm .................. 348 ft 1. IIt $7 ft 1. qm .................. 447 ft 1. 631 ft 1. rpm .................. 500 ft 1. 891 ft 1.

tC.ionary. ................ 126 ft 1. ft 1.

2 ed%n rather than mean values were used Beck se the 30 point scale W #IS vi dud in to equal inte:nsity intervals.

APP ss A RC3 ThING ARC-LINE

EFERENCES

istortion in the perception of real movement. 9. cxp.

57. Light adaptation and brightness enhancement. Percept.

RTLEY and R. EWELL, 1963. Effects upon bright- gth of the null interval separating

es: Sensory implications for the Alternation J. Psychol., 56, 99-406.