submission - Independent Pilots Association

It is also note'lonhy that, uhile we obsen'ccl a decreâsc in accwac.,r/ on rhe gram:naúcal
reasoniugtask,imparrrrentof th:sperformurce parameter was not ccnparable to thar p;oducod
by a BAC of 0.107â' \ltile this nray a¡ first cont¡adict u\e suggesrion thar in rhis srudv
vulnerability to sustained wakefulncss was, [o E lârge degree, dercrmi¡:cd by rask compiexity. rr
should bc notcd th¡t pa¡ticipa¡fs rr'ete insuucted to concentatc on a;curacy rather rhan speed
when completing the grarnmalcal reasoning task. Thus, our partrcula¡ insrnrcdons ro
puticipants may uplaiu- at least in pan rhis irrcgu.¡ariry. Alremadvely, rhis finding is in lir¡c
with the suggesúon of a narnral 'speed-accuracy tade-off. Sirnil¡¡ resulLr have been obscrred in
5sveral studies, ç'hich repoÍ a cecline i¡ speed of performance, but nor accurac)', when s,leep-
deprived subjects arerequired to pcrform a logical-reasorung task (Ângus and Hcstegrave, 1985;
Webb and Lcvy, 1982).
lnreresunrl¡', this was not the c¡se '¡'ith the vigiJarce task. In rhis ies:rnc:, despite ir--\:ructtcn
to cooccntrate pnmanll'on acct[acy, this componcnr \as shEhtly nore w.nerelle to sleep
deprivation than r¡'as resp.ersc latency The absence of a tade-off on this rask na1, bc eçlaincd
by the diffcrent propenies of the vigilancc and grammatical rcasorung tasks. In accordance u.:lh
the distinction raiscd þ Broadbent (1953). :he laner oirhesc rasks cs be defìncd as arr u¡pêccd
lask, in which the subject cetermi¡es thÈ ral.e Of stjmuli presenurlion In contras(, tbe rigjlsnsç
task can be defined as a paced task, in which stunuli are presenteC a'. a spced controlled by the
experineilcr. ln linc rrith this distrnction, our 6nClng. ar: consisteot r¡'irh thosc of B¡oaJbent
(1953) who observed ùur while a paccd task raprdly detericrateC durin3 ùe exp:rimen'.al pcriod,
in tcr¡ns of spccd, an unpaccd ve¡sio:: of t.re same t-k dr,l, nor