Intersensory discrimination of signal duration using visual and auditory signal

Atkinson, R. C.

Patton, R. M.

Tanner, T. A., Jr.

English

NASA Technical Reports Server

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-, * h ,  * .  I 
a Paper t o  be presented at 
Flor ida,  May 11-14, 1964 
, 
i L 4 , i  1 1 I . t  + i * I.: I > 
Aerospace Medica Association Meeting, M i a m i ,  
Trieve A. Tanner, Jr., B O D o  
R. Mark Patton, Ph,D. 
Ames Research Center /p/s/f 
R. C. Atkinson, Ph.D. 
Stanford University 
The quant i ty  of experimental. data t h a t  have been obtained i n  the  
a rea  of t i n e  discrimination i s  surpr i s ing ly  meager compared t o  the 
information avai lzble  i n  other psychophysical areas.  A t  l e a s t  p a r t  
of t h i s  infomation-lag can be a t t r i bu ted  t o  a lack  of agreement con- 
cerning the nature of the  perception of time, 
t rea ted  at times as  a dimension of the  other  sense modd i t i e s  aqd at 
Time perception has been 
times as though it involved a separate sense. Lack of information 
concerning the  cen t r a l  physiological mechanisms associated with time 
perception has contributed t o  the problem. Thus, for exzzple, while 
resezrchers ha-Te bves t iga t ed  such a t t r i b u t e s  of the  v isua l  s t i m u l u s  
as in t ens i ty  end hxe, the d i s c r i d a t i o n  of the  duration of the stimulus 
has been avoi"ud,zs thou& it involved a separate sense mode, 
Most of the research concerned with time d i sc r imba t ion  has employed 
auditory s t h u l i ,  
be d i s c r h i n a t e d ,  o r  ,auditory cl icks  have been used t o  m r k - o f f  "empty" 
Pure tones have been used t o  denote the  L?terval t o  
time i n t e r v d s ,  A fev s tudies  have invest igzted the discrimination of 
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v i sua l  durations. To the extent t h a t  t he  s tud ies  using v i s u d  and 
auditory stim.li a re  corparable in  design, t h e i r  r e s u l t s  are i n  general  
agreement, 
and A t  = the  difference threshold, i o e o ,  t h a t  increment i n  t i m e  t h a t  
For exmple,  the Weber Fract ion A t / t  = K (where t = t,& 
-J' I ' 
i s  discriminated with a probabi l i ty  of .n), seems t o  hold at about 1:lO 
f o r  durations i n  the  region of one t o  two seconds. 
Essent ia l ly  no data  have been presented t h a t  are  the result of 
d i r e c t  cornparisons of v i s a  and audi tory s igna l  durations. The present 
study xas designed t o  supply information concerning such cross-modality 
compaisons, I n  t h i s  study, v i s u d  and auditory s ignals  were presented 
f o r  both i n t e r -  and intra-modality comparisons of duration, using a 
s tmdard  two-choice, forced-choice experimental. design. 
Subjects,- The experimental subjects  were twelve male college 
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freshmen and sophomores, ranging i n  age from seventeen t o  tsrenty-two 
years. All were f r e e  from at l e a s t  gross  v i sua l  o r  auditory impairment 
as de ten ined  by an inTormal interview. 
Apoar~tv.s.- The subjects  sat i n  a dimly l igkte6,  soxnd attenuated 
room, vearing easphones, 
were mounted on a display panel i n  f r o n t  of t he  subject,/sho;in i n  
Figure 1, 
A 7nm diameter lens ,  and tm p x h  buttons,  
2.3 
The push buttons were used t o  record the  subject's response. 
The acdi tory s ignal ,  a lOOOEz (cps)  tone was presented kkrough the  
earphones (Permoflux, D4S-17) at a moderate bu t  c l ea r ly  discriminable 
l e v e l  of i n t ens i ty ,  
presented through the earphones at a considerably lover i n t e n s i t y  than 
A white noise ( lOOKHz,  l o w  pass )  bzckground was  
- .  - *  
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t h e  tone. 
tube (Sylvania, F U l 3 l C ) ,  w a s  mounted behind and w a s  viewed through 
The l ight source f o r  the v i sua l  stimulus, a glow-modulator t 
c 
the  lens  en t h e  panel, Both the l i g h t  and the  tone were gated by 
a so l id  s t a t e  switch, 
Procedure,- Each of the  twelve subjects  was  t es ted  f o r  a t o t a l  of 
24 experimental sessions, each session consis t ing of 512 trials. On 
each t r ia l  two sigqds of unequal durations were presented; t h e  first 
sign33 W L ~ S  longer on one-half of the trials, shor te r  on the  other 
half .  The subjec t ' s  t ask  w a s  t o  judge which of the  two s igna ls  ws 
longer by pressing one of the  two response switches on the  display 
panel, 
Three d i f fe ren t  pairings-of -durations w e r e  investigated: 0.5s 
(seconds) with 0 . 6 ~ ,  1,Os with lols, and 1.5s with L ~ S ,  (hereaf te r  
these pair ings w i l l  be designated by the  base durations, 0,5, 1.0, and 
1.5, respect ively) .  The incremental duration was constant a t  0.1s. 
Only ore of the  th ree  base durations was  presented d m i n g  a s ingle  
experixental  session; thus, the 24 sessions consisted of e ight  sessions 
with each of the three  base durations. 
Each s igna l  consisted of a l i g h t  o r  a tone, so t h a t  on any given 
trial th2 subject  was presented e i t h e r  two lights (Sw), two tones (S,), 
a tone followed by a l i g h t  (SAv), o r  a l i g h t  followed by a. tone (SVA)" 
A trid. begm with the  onset of the background noise and ended with 
i t s  o f f se t ,  The sequence of events on the  trial and t h e i r  durations were 
as follows: noise d o n e  ( ready  period),  1,Os; noise plm first  signal, 
X E R O  XERO X E H O  
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. .  . .  . .  
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varied duration; noise done ,  0.8s; noise  plus second s ignal ,  var ied 
duration; noise d o n e  (response period), z o o s ;  no noise ( i n t e r t r i a l  
i n t e rva l ) ,  2 . 0 s ~  
The eigl?t types of trials, consisting of  the four  s t h u l i  (%, 
and SvA) times the  two orders of s igna l  duration ( f i rs t  o r  ‘AA’ ’AV’ 
second s igna l  longer)  were presented throughout a given session i n  a 
sequence t h a t  w a s  randomized within blocks of 128 trials, with 16 of 
each of the  t r i a l - types  i n  each block. 
RESULTS AND DISCUSSION 
I n  Figures 2, 3 ,  znd 4, each da ta  point  i s  an averag- of the  
perfcmaqce of the twelve subjects. 
of a correct  response, Pr(Rc), p lot ted over t he  e ight  sessions f o r  
each of the f o u r  s t i m u l i ,  
the  data f o r  one of the t h e e  base durations. 
base duration conf o m s  with previously published r e s u l t s  showing t h a t  
t he  difference threshold f o r  two audi tory sign_als is  approximately 
one-tenti; oii base durations near one second. The evidence i n  Figure 2 
t h a t  performmce becomes more accurate as the  increlrental dwa t ion  
becomes l z g e r ,  r e l a t i v e  t o  the  base duration (as A t / t  becoaes l a r g e r ) ,  
i s  a l s o  consis tent  with the r e su l t s  of previous research. 
Figure 2 shows the  probabi l i ty  
Each of the three  graphs i n  F iewe  2 displays 
The SM curve f o r  t h e  1.0 
Disc-inination of s igna l  duration w a s  most accurate when two 
auditory s igna ls  were compared, 
is  higher than the other curves over each of the sessions,  
evidence of the  superior accuracy i n  judging two azdi tc ry  sigrnals i s  
given by individual  subjects’  d a t a ,  
performed S e s t  t o  SAA, with each base duration, as follows: 
For each base durztion the  SAA curve 
Additional 
O f  t he  twelve subjects,  a majority 
nine with 
X F P O  . - _. - 
. C  
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0.5 ( p <  .001), t en  with 1,O (p<  .001), and e ight  with 1.5 (p  =e .0024). 
Kext most accurate seem t o  have been judguents conparing 'the 
% durations of two v i sua l  signals'. For the  0.5 base duration the  
curve steads c o q l e t e l y  above e i ther  the E+A or SAv curves The, 1,O 
and 1.5 graphs, ho-dever, show tha t  t h i s  super ior i ty  decreased as t h e  
base duration became longer (as A t/t becomes smaller) .  
The accuracy of performance when both s igna ls  were presented t o  
the  s m e  modality, (S,u S,), w a s  compared with the  accuracy of 
per fommce when the  si&nals were presented t o  d i f f e ren t  I-o?sl-ities 
( SAv 'd SvA) Again, considering the  performance of ir, c t s ,  
a majority perfomed b e s t  t o  S 
follows: 
nine with lo5 ( p  = .,14>+ 
Sw, with each base duration, as 
twelve with Oe5 (p<.002), eleven with 1.0 (p  = .006) and 
Figure 3a, Fr(ft I SAvuSvA), shows for each of the  three  base 
duratiocs,  the probabi l i ty  of a judgment t h a t  t he  13sual s igna l  w a s  
longer, ??r(%- >, given a s t b u l u s  requir ing a cross-nodality coaparison, 
SAv or S 
than the auditory i n  each session with the  O.5-base dxration. 
s ider icg  the  individual subjec t ' s  da t a  (0.5 base duration),/ele-Ten 
The f igure  shows tha t  t he  visual s igna l   as judged longer VA 
Con- 
f o r  
of t he  twelve subjects the  probabi l i ty  of judging t h e  v i sua l  sip-al 
longer t.hm %he Euditory was above 0.5 (p< .006), With base &nat ions  
1,O and la?, the bias toward judging the  v i sua l  s igna l  as longer 
d imin i shdo  With the le? duration t'nere i s  a suggestion t h a t  the  
b i a s  ' rss been reversed; over SLY of the 1ia-t sessions,  the probabi l i ty  
of judglsg the  v isua l  s igna l  longer i s  l e s s  than O e 5  2nd only four  of 
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the  tvelve scbjects  judged the  v isua l  s igna l  longer more of ten  than 
the  auditory. 
The re la t ionship  between P(%) and base duration holds, regardless  
of the order of presentation of the v i s u a l  md auditory s ignals .  This 
i s  shown by Figures 3 and 3c which present Pr(X, I S ) ard Pr(% 1 SvA),, AV 
F i g a e s  4a arid 4b present Pr(Rll S ) and Pr(% S,), t he  w 
probabi l i ty  of judging the  f irst  s igna l  longer than the second, given 
Sw ard S respectively.  I n  these two cases, where s ignals  of t he  
same modality a re  compared, there  i s  an order e f fec t .  
these s t inu lus  conditions, it will be seen t h a t  Pr(R..) decreases as 
t h e  base durztion increases ( i e e e ,  as A t / t  becomes smaller) .  
other words, as t he  discrimination became more d i f f i c u l t ,  there  was an  
increesicg tendency f o r  the  second stihulus t o  be reported as longer. 
It w i l l  be noted t h a t  t he  0,5 probabi l i ty  l i n e s  of Figures 4a and 4b 
represent xrrbiased performance with respect  t o  the order of presentation, 
The responses t o  S and Sa are  arranged d i f f e ren t ly  re lz t i - re  t o  the  Oe> 
prob3bi l i ty  l i ne .  
t o  respond t o  the  second s igna l  as longer. 
t o  SM, hoxever, the  shor te r  base durations =e a l w r ; s  associated with 
a grea te r  t h m  0,5 probabi l i ty  of judging the  f i r s t  sigrml. as longer, 
I n  addition, there  i s  an apparent tendency f o r  t he  respccses t o  S 
converge t o w a d  0.5 probabi l i ty ,  i.e., f o r  b iases  t o  respocc? more often,  
e i t h e r  t o  the f irst  o r  second signal, t o  disappear. 
does not occur i n  the case of responses t o  S 
PA' 
For both of 
I n  
w 
I n  the former czse there  i s  virtudl7 always a b i a s  
In  the czse of responses 
to AA 
This phenonenon 
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To conclude, the  r e s u l t s  of this study have given evidence of 
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the  following: 
1, Compxative judgements of s igna l  duration =e more 
accurate when the  two s ignals  are presented t o  the  s m e  sense 
modality t h w  when comparisons must be made across mcdalit ies.  
I n  oddition, comparisons seen t o  be more accurate when t h e  two 
s iga l s  are  auditory than when they a re  visual .  
2, Additional analysis showed t h a t  within the  range of 
durations investigzted (005 t o  l05 seconds) the  tendency t o  
judge the  v isua l  s igna l  t o  be longer than the  auditory seems 
t o  increase as the incremental duration becomes a l a rge r  portion 
of the  base duration. 
3. Where s ignals  t o  the sane nodal i ty  a re  c c q a e d ,  the  
probabiliity of the  f irst  signal being chosen is  a function of 
nt/t 0 
4, It is  suggested tha t  any theory which intenzed t o  
r e l i t z  the  judgment of time t o  s ignal  duration nust t z k e  i n t o  
accoant the  sense modality stimulzted by the signal a s  wel l  
a s  i t s  duration, 


Inter-sensory Judgments of Signal Duration

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