Approaches o the Srudy ofBehavior Behavior can bc dctued rs dre way ar arimrl responds o srim- uli in its enviromrcnt. A stimulus might bc as simple as detec- tion ofthe presencc f f<x)d n the enlironmcnt. n rhissense, a bacterial ell "behaves" lv moving oward highcr conce,rcm tions of, sugar n its surrouDding mednun. This lxhavior is verv simple nd is well suitcd o rhe ife ofbactcria, alloving these rganisms o tive and reproduce. \" rnir|lrl, rohrd. h r 1 uccupied iFercnr.r\ ron,nenrs rnd ficed diverse roblcms har affected hcir surrival Dd re- production. heir ne*ous slstems nd behavnrrorconitandy becrDre more complex. Ncnrus sr,stems ercive and process information and trigger adxptive rocor esponses, vhich e see as patterns f behavior Behaviot's two components are its immediate qause and its eyolutionary origin Itrt crn talk about animil beh:rvn,r n nvo diflerclt ways. irst, rvc minht ask r-o ir all vorls-that is, how the animal senses, ncivc Detworks, r internal statc provide a physiolosical :rsis for thc behavior. he "how" of behavior s a question abort praximat ,trilti|n. To anih'zc rhe proimdte cause f behav- io1 se nighr lreasLrre ormone evels or record he inpulse activiF of neurons n the animal. .or onrnple, a male songbird nlay snlg during dre breeding cason ecause f an increased lere1 of thc steroid sex hormonc estosterone, vhich binds o receptors n the br:rin nd triggtrs he prodnction ofsongi rhis erphmtion r.ould describc he pro:rimate ause f the male br ,1, 'ng. llrZr a behalior evolved an investigation fits adaptilc value is a question conccming Lbj,Mte u L . tian. To studv thc ultimate cause f I behavior, 'e attempt o dcternine horv t inllucnc.d he ani'n 's sunnd or reproductivc uccess. rnrle bird siDqs o defend territorv FrD orher mrlcs and o actract a cmilc with \drich to reproducei his s the ultinraer or evo- l:Li,,rrr. <rpLn:rior br hc,,,d1(\ o, Jli/J ,,n. The sudy of behar rr has a d a ong historv ofconn oveny. Onc source of controveny has been he quesrion f whethcr behrvnlr s dercrnined norc bj.an indilidurllsgenes r bl its lellrning nd experieDce.In thcr s.ords, s bcharior he esult of mturc (nlsnnct) r nurnrre cxpdence)? n thc past, his ques- tion was considered n eithcr/or proposition, rurrr now roon s s n Jigure 4.1 TNNATtr .GG-RoLIING RtrsloNsF rN .;F ssE. hc series fnryorents rscd bv r goose o retncvc N egg s r iixed act,on rnern. ()ncc It detects hc sign sdlDulus in thh case, n egg ou6 c ihe esr), he soosc ocs drough the ortirc scr ofnovelnenrs: rrilleltenditsneck td d the egg, ecr nP, dnd n)llthc ceg back nto thc ncsr ith r slde-to-sidc orion ofirs neck whilc he egg n tuckerl cncafi ns bill. 1116 t.nVIII-"1"y .,,i h.ht,,i- that i tinct and experience oth phy significant oles, olicn interactiry in compl€r war,s o producc drc final beh;rr or. Innate bebavior does not require learning Earlv esearch n the 6eld ofanimal behrvn,r ncused n behav- iord patterns hatare ah-avs xhibited mcnlrcrs ofr species ir rcsponsco a particrlar stirnuluq hat is, thel'appered to be instinctivc, or innate, behaviors. Bccause behrvior is olicn stereog?ed appenring n the same way n different ndnidu, als of r qrecics), hese early esearchers rg"ued hrr ir nrst be b$ed on prcsctpaths n rhe nenous systcn.In their .ie$, hcse paths are structured iolr genetic lucprints and cause nimals to show cssentinlly he same bchavnrr ron the first time it G produced hroughout heir ivcs. These esearchers ased ieiropinions on bchavn,rs uc h as cgtaetieval bygeese. ecsc ncubate heir eggs n a nest.lf a goosc notices hrt rn egg has been knocked ut of thc nest, it will cxtend ts Deck oward hc cgg, get up, and roll the eg g back nto the nest ith a side-to-side orior ofits ncck vhile thc cgg s nrcked beneath ts ,ill (figure 5+.1). Evcn {the eg g is rcmoved during etrieval, he goose ornpletcs he behar-ior, rs if driven b1' a program released by dre nitirl sight of the egg Egg retrieral behrvnr is triggered bl, i sign stimulus, the rppcarance frneggoutoftie nest. A componert fthe gooset ncFous svstem, he innatc rcleasirg mechanism, provides he neural nscructions or the motor progrrn, or ixed action pat- tem, involved r egg rcnieul. \'lore generally, he sign srimulus is r sigu.l n the cnvironDrent hat riggcn a behavior. he ir- nare elersing mechanisnl s he sensorl mechanisn hat detects thesignal, mcl he ucd action :rftemis hc stcreorvped ct. One interesting aspect of sign srimuli is th:t $ey lrc often not €ry specific; n sorne simations, vide varietv of ',brrcr. ill nggr r rrrrd acrion ,ncrn. ,,r errrrrple. , * . $-ill attenpt to roll basebrlls nd even lcer cans acLilto their nesrs. Moreovcr, once rhe objects arc in rhe nest, hc g<rxe recogDizes hrt thev are not eggs nd emoves hernl A similar cramp)e s provided by nrle sticUebicL ish. During the brccdnrg eason, maies dcvcl<,p right red col<,r ation on their undcrsides. eritorirl males eact aggrcssirclv to the rpprorch ofolher nales, perfi,rnring m rggressivc li s * * l
