deprivation level s used in this experiment do not enhance performance in the ... Burgess Pub. Co., 1962. Bryan , ~1. ~1. ... New York: John Wiley. & Sons, 1953.
Bl!owu sslon
The apparent dis crepancy be twee n the pre s ent s tudy and the previous studies which indicated th at driv e summa ti on occurs in the water escape ta sk can probably be exp la ined on the ba si s of the comple xi ty of the tasks us ed . The s tudie s by Mor ey (1934) and Braun et al (1957) used ma ze s . The s tudy by Levine et a l (1959) ca nnot be so s imply explained , since th ey too u sed a s traight runway. It will be r ecalled that th ey ran th eir Ss in water a t room temperature , and they used pretrial shock to " a ctivate" the animals . ltha s been shown in the pres ent study that s wimming wa s not at an asymptote in th e warmer temperature, so it is reaso nab le that more ac tivate d animals could perform fa ster. The effec ts of pre-trial shock a re ap pa rently greater than the effects of 72 hr . pre-trial food deprivation. It r emain s to be s ee n wheth er shoc k prior to s wim ming will enhance swimm ing s peed in 150 C water. It seemed appa rent that by the sec ond day lea rning was comple te and performan ce was the only variable
A method of measuring brain lesions ROGER K. THOMAS, JR. AND L. J. PEACOCK UN IVE RSIT Y OF GE ORGI A
Abstract It was not ed tha t the mo st frequ ently u s ed method of mea suring brain lesions is probably the planimeter . The plan im et er method is ti me cons umi ng and pl animeters a r e not r eadily a vailable to mo st psychologi sts . The dot gr id method was de s cribed and r ecommended for its savings in effort and expe nse with negligible sacr ifice of accuracy . Problem Ca r tographe rs (Robi nson, 1953) and for e ste r s (Spurr, 1948; Ave ry , 1962) have dev is ed se veral methods of de termining the a r ea of ir r egul ar fi eld s. Psychologists someti mes need to determine irregular a reas as in the case of cor tical abla ti ons . The majority of psychologists using rats as Ss hav e employed La shl ey brain di a grams (1929)·to de te r mi ne th e a mount of corte x r emoved . The mo st frequent method u s ed is that of determining a rea with a planimete r. Thi s is a prefe r red method for its accuracy, but it is time consum ing , and the pla nimete r is an expens ive ins t ru me nt . Some psychologi sts have us ed weight appor tioning m ethods, but thi s is very ti me consuming and ha s le s s accuracy. An alter na tive to both the s e technique s that psychologi sts have appa rentl y overlooked is the dot grid metho d . This i s inexp en sive, quick an d accurate. There a re oth er technique s ava ilable for a r ea determination, but th e pre sent writers wish to des cribe and recomme nd the dot grid method . )Il"hod Avery (1962) not ed th at dot grids ca n be pu rchased or imp ro vised inexpen sivel y. One commercially a vailable dot grid wa s pr epared and de scribed by Br yan (1943), and this can be purcha sed at fore stry supply hou s e s . A dot grid can be im provi sed by marking a transparent 184
th en being studied . It mu st be concluded that th e depriv ation lev el s u s ed in th is exp e riment do not enhanc e pe rformance in the wate r escape runway; howeve r , th e data conc er ning the numb er of times the food was ta ke n indica te d that the food had different value in the two temperature condi tio ns . Speci fi cally, the food was sought le s s after th e experience in th e colde r water, ind icating the rats were mo r e "conce r ne d" with oth er thin gs afte r being in the cold wate r . It should be r e called that after the first day the ani mals were les s deprived , and it could be that inc r easing the deprivation period prio r to th e second and third experimental days would produce different r e sults . References Braun , 11 . W., wedektnd , C . E ., & Smuds k i. ,I. F. The effec t of an i rr ele vant dri ve on maze learning in t he rat. J . CTp . P sy c ho l . , 1957, 54 , 148- 152. L evine , S., Staa ts , S. A . , & F rommer , G . Dri v e summat i on i n a wate r maze . F su ch o ] , I1cp. , 1959, 5, 30 1-304. ~Io rey . R H. Swimmi ng spee d of ra ts as a fun ct i on of t he pre sen c e or absence of sound J . co mp . P sy c ho I .. 1934, 17. 329-354.
shee t of aceta te at 1/16 in inte r va ls ; thu s the grid conta ins 256 dot s per s quare in. Greater or les s accuracy ca n be obtain ed by decreasing or inc reasing the spacing of the dots. The dot gr id i s placed over the ce rebral cor tical portion of the La shley diagram and the num ber of dot s falling within the figure are counte d . Three r eadings are r ecommend ed to assure accuracy; an ave r age of the readings may be taken in the event they do not agree. Bryan (1943) r ecommended counting eve r y oth er dot that falls on th e bound ary lin e, but th e pres ent writers suggest equa l accuracy will be obtai ned by counting a ll dot s on the line of the brain di agram and on the lin e dem arcatin g th e lesion . The number of dots in the le sion divid ed by the number of dot s in th e brain di agram gives the pe r cent of cortex which ha s been remov ed . Bhwusslon
Abe ll (1939) r eported tha t the dot grid meth od ha s 1.84% e r r or compared to planimeter contr ols . It was not pos sible to dis cern fr om Abe ll 's s tudy what his dot grid int erval was . It is pos si ble that the er r or is le s s in the dot gr id spacing de s cribed he r e (i. e. 256 dot s / sq in). In any eve nt , a two per cen t er r or is quite tol erabl e when th e advantages in ti me, effort and expe nse a re cons idered. References Abell, C. A . A met hod of estimating area i n irregularl y sha ped and brok en fi gures J . Forc s t ru , 1939, 37 , 344-345 . Av ery , T . E . I nt erp ret ati on of aeria l ph o t ogra ph s . Mi nneapoli s: B urgess Pu b. C o. , 1962 . Bryan , ~1. ~1. Ar ea det ermi nations wit h the modified acre age grid . J . F ore stry , 1943, 4 1, 764- 766. L ashl ey , K . S. Bra in mechani sms and i nt ellig ence. Ch i c ago: University of Chicago Pr ess , 1929 . Robinson , A. II . E l e ment s of cartogra phy . New York: J ohn Wil ey & Sons , 1953 . Spurr , S. II . A eri a l pho t ograp hs in f ores t ry. P ress , 1948.
New Y ork : Rona ld
P sy ch on . Sci ., 1965 , Vol. 3
