M asato IshidaOsa ka U niversity of E duca tion, Osa ka , J a pa n M auricio R. Papin i Texa s Christia n U niversity, Fort Worth, Texa s, U.S.A.Two exp erim en ts w ith tu r tles (Geoclemys reev esii) exam ined th e overtrain ing extinction effect (O E E ) an d th e overtra ining reve rsal effect (O RE ), u n d er m asse d train ing con d ition s. In E xp erim en t 1, th ree g ro u ps of tur tles received 7, 14, or 21 sessio n s of tr aining in a r u nw ay situ atio n for food reinforcem en t, follow ed by 15 se ssio ns of extinction . E xtinctio n w as faster, th e greater th e nu m ber of acqu isitio n sessio ns. In E xp erim en t 2, the tw o g ro u ps of tu rtles lear ned a sp atial discrim ination for food reinforcem en t either to a criterio n (19 of 20 cor rect re sp o ns es), or to th at criterion plu s 100 add ition al trials of overtr aining. W h en th e validity of th e p osition s w as reve rse d , lear nin g w as faster for th e over tr ained gro u p tha n for th e gro u p tr ained to a criterion . T his eviden ce of th e O E E and the O R E is th e ® r st yet rep or ted for a re ptile. T h e resu lts are d iscu sse d in th e fr am ew or k of com p arative re sear ch on rew ardsc hed u le effects.
Turtles1 trained und er m assed cond ition s show g reater resistance to extin ction after acq uisition w ith partial than co ntinuous rein forcem ent. T his phenom en on, called the partial rein forcem ent extinction effect (P RE E ), w as reported in three studies in w hich several trials per sessio n an d a relatively short intertrial interval (IT I) w ere u sed (Ishida & K itam ura, 1988; M urillo, D iercks, & C ap aldi, 1961; W ise & G allagher, 1964). Shef® eld (1949) sug gested that the P RE E occurs becau se the aftereffects of rew ard an d no n-rew ard becom e part of the stimulu s com plex co ntrolling instrum ental perfor m an ce. Becau se a partial reinforcem ent schedule involves training to respond w hile under the in¯uence of the aftereffects of no n-rew ard, a shift from acquisition to extinction is less discrim inable TH E Q UA RTER LY JO U RNA L OF E XPE R IM E NTAL P SYCH OL OG Y, 1997, 50B (1), 1± 16Requ ests for rep rin ts sh ould be sen t to M . Ish id a, D epartm e nt of Psych olog y, Osaka U niversit y of E ducation , 698± 1, 4-C hom e Asah ig aoka K ash iw ara-C ity, Osaka, Japan 582, or to M .R . Pap ini, D epartm ent of P syc hology, Texas Ch ristian U niversi ty, Fort Worth , TX 76129, U.S.A .The re search rep orted in this article was sup ported by G rant 066100 74 (to M .I.) from the M in istry of E ducation , Jap an. The author s wou ld like to than k Saeko M aeno for colle cting part of the data. 1 In Britain, sem i-aqu atic chelonians are re ferred to as``terrap in s' ' . The name``tu rtles' ' is kep t here for consiste ncy with its prevaili ng use in the literatu re.Ó 1997 The E xp erim ental Psych olog y S ociety for partially reinforced an imals than it is for co ntinuously reinforced an im als. O n the assum ption that stimulus aftereffects decay in time, the car ry-ov...
