Allan - Is There a Constant Minimum Perceptual Duration!

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Qua rterly Journal of Experimental Psychology 1976) 28, 71-76

IS THERE A CONSTANT MINIMUMPERCEPTUAL DURATIONL O R R A I N E G. A L L A N

Department of Psychology, McM aster University, Hamilton, O ntario, CanadaIt has been suggested in the recent literature that all stimuli briefer than a criticalduration have identical perceptual durations. Relevant simultaneity, reaction time,temporal order and duration discrimination data are discussed, and new data arepresented. It is concluded that the relationship between the physical duration ofa stimulus and its perceptual duration is not yet understood.

IntroductionEfron 197oa,b,c,d,1973)has extensively investigated th e relationship betw een t hephysical duration of a brief stimulus an d its perceptual duration. I n his experi-m ents th e observer is required to m ake simultaneity judg em ents about two events.He has concluded that for stimuli which are briefer than a critical durationapproximately 5 ms), perceptual offset latency increases as stimulus durationis decreased. T h e result is a constant perceptual duration. T h e duration of theperception of a brief stimulus has some fixed minimum which does not becomesho rter regardless of how brief the physical stimu lus is. So m e aspects of thesimultaneity data obtained by Haber and Standing 1970)are also consistent w iththe minimum duration hypothesis.A constant minimum perceptual duration has implications for performance inan offset reaction tim e task, for temporal ord er discrimination, an d for jud ge m en tsabout duration. If perceptual offset latency were a n inverse function of stimulusduration, one m ight expect to find that th e reaction time to stimulus offset is alsoan inverse function of stimulus duration. Neither t he offset reaction time data ofRobinson 1 9 7 3 )nor of Briggs and Kinsbourne 1 9 7 2 )supp ort this expectation.Fo r brief stimu li, offset reaction tim e is best described as independent of stim ulusduration.Consider a temporal order discrimination task where the first stimulus is pre-sented for d ms, followed t ms later, by a second d ms stimulus. If there is aconstant p erceptual duration, tmin, the n for com binations of d = k , where k isa constant, one would expect no variation in temporal order discriminationperformance, for k < mln. Data reported by T ho r and Spitz 1968) ndicate thatord er discrimination performance is no t constant for a con stant value of d .If the perceptual duration of brief stimuli is constant and independent ofstimulus duration, the n discriminations between stimuli briefer th an th e min im umperceptual duration cannot be based on perceptual duration. Allan and Kristof-

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72 L. G ALLANferson ( I 974) reviewed a nu m be r of duration discrimination studies w hich indicatetha t discrimination performance is inde pen de nt of detectable man ipulations of theenergy dimensions of brief stimuli. T he y concluded that the available durationdiscrimination literature suggests that the discriminations are based on temporalinformation rather than on other cues which were also available. It could beargued tha t th is conclusion is inconsistent with t he m inim um duration hypothesis.It should be noted that while the data of the two observers reported in Efrons1970 simultaneity studie s provide strong sup port for th e min im um durationhypothesis, perceptual duration is no t precisely constant Efron, 1973, p . 724)for either of the two new observers in the 1973 study. Also, while un de r oneexperim ental condition t he data of H ab er an d Standings 1970) one observer wereconsistent with the minimum duration hypothesis, under the other conditionsthe data were not.

I n sum , the main support for the m inimum duration hypothesis is providedby the simultaneity studies. T h e available reaction time data an d temporal orde rdata are inconsistent with expectations generated by the minimum durationhypothesis, and the conclusions of Allan and Kristofferson 1974) have yet tobe reconciled with th e m inim um duration hypothesis. It appears, then, that therelationship between stimulus duration and perceptual duration is not yet estab-lished. Asa first step, replication of Efrons basic finding was attempted. Th es e resultsare presented i n this brief note.A series of studies to investigate this relationship was undertaken.

MethodThree observers participated in this experiment. Two of the observers,LA (the author)and ABK, knew of Efrons results. The third was naive with respect to the psychologicalliterature, and was paid for his services.The procedure was similar to that used in Efrons (1970U) auditory offset-onset simul-taneity experiment. The observers task was to adjust the temporal relationship betweenthe offset of a 72 dBwhite noise burst and the onset of a 500 ms, 72 dB, 2000 Hz tone so thatthe two events were simultaneous. He was seated in a dimly illuminated, IAC soundattenuated chamber. Each hada rise-decay time of 2.5 ms. Stimulus presentation and timing, and response recording were

under the control of a PDP-8/S computer.At the beginning of the trial the two stimuli were presented so that there was an obviousgap between the offset of the noise and the onset of the tone (from 150 to 190ms in 10 mssteps, randomly determined). On succeeding presentations the gap was shortened by10ms steps until the observer reported that there was no longer a gap between the noiseoffset and the tone onset. The two stimuli were then presented so that the tone onsetobviously occurred prior to the noise offset and on successive presentations this overlap wasshortened by 1 ms steps until the observer reported that there was no longer an overlap.Thus, on each trial there were two response measures: D1,he temporal offset/onset intervalin milliseconds at which the transition from a gap response to a no gap response occurred,and Dz he interval at which the transition from an overlap to a no overlap response occurred.Positive values of D and D2 ndicate that the transition occurred when the noise offsetpreceded the tone onset, negative values the reverse. The mean of the two measures, D,was also determined for each trial.Ten values of noise duration, d , were used 10, 0, 50 70 90 110, 150, zoo, 300 and500 ms). There were 10 rials per session, each value of doccurring once during a session in

The noise burst and the tone were presented dichotically.


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74 L. G ALLAN

-40

100 200 3 4 500d

FIGURE.observer. (a) Observer A . B . K . (b) Observer L . A . c ) Observer J.R.Th e mean valu e of D in milliseconds as a function of noise duration, d for each

function of d , with slope - I . For values of d larger than the critical value, theslope should be 0. I t is clear from Figure I that for all three observers the slopeof the decreasing portion of the function is considerably larger than -I .to be larger than 5 .

For each observer the mean value of 5 ver the 10 alues of d is larger than themean value of D 54.17vs. 49.42, 9.67 vs. 2.89, -4.22 vs. -11.67 for observersABK, LA and JR, respectively). T h e value of th e temporal interval betweennoise offset an d tone onset at which the transition from one response to anotherresponse occurs depends up on whether th e series is descending gap to overlap)or ascend ing overlap to gap).F r o m T a b l e I i t can be seen tha t the standard deviations o,,a and o are notsystematically related to d .

Inspection of Tab le I reveals that the re is a tendency for

Discussionan d stimulus duration observed in this experimentcan be taken to demonstrate that for brief stimuli perceptual offset latency in-creases as stimulus duration is decreased. However, the results do not support

T h e relationship between

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PERCEPTUAL DURATION 7

th e prediction tha t stimulus duration plus offset latency yields a constant per-ceptual duration.Robinsons 1973) data can be interpreted to demonstrate that perceptual offsetlatency is constant an d indepen den t of stimulus duration. I n order to integratehis data with Efrons, he suggested that more than one temporally distinctrepresentation of stimulus offset occurs in th e nervous system p. 282 .Another possible explanation of the discrepancy between the simultaneity dataand the offset reaction time data is that D s not a good measure of perceptualoffse t latency. T h is possibility is suggested by the different values of El and E2th e variability in th e form of th e function am ong th e three observers in th e presentstudy, and the lack of similarity between these functions and Efrons functions.T h e simultaneity data are generated in experim ents employing psychophysicalmethodology which is known to produce changes in performance which oftenreflect variations in response strategy, and data which are difficult to replicateacross laboratories. I n fact, in discussing his own data, Efr on 1 9 7 0 ~ ) onsidersthe possibility that his results could be interpreted as a systematic change in theobservers criterion for simultaneity which is induced by changing the durationof th e first stimulus. H e concluded that T he re is no evidence available whichsup po rts th e view th at su ch a mathematically regular change in subjective criteriain this psychophysical experiment could have been induced by variation of thedura tion of th e first stimulus p. 53). While it is true that there is no directevidence to indicate that Efrons results are determ ined by criterion changes, thereare data in t he literature which show th at changes in criterion do occur as a functionof stimulus changes, and that the nature of the change is highly variable amongobservers Allan, 1968; Kinchla a nd A llan, 1970; Kinchla and Smyzer, 1967). I na recent article Swets 1973) has brou ght together evidence to show that . . h eeffects of biasing factors on t he rep ort have often been viewed as properties ofthe discrimination process, with the result that incorrect conclusions have beendrawn about the nature of perception p. 991). Given the possible roleof changes in criterion as a function of stimulus duration, it would be wise infurthe r studie s of th e relation between stimulus duration an d perceptual durationto u se psychophysical me thods which allow one to evaluate th e role of criterionchanges.In sum, the failure to reproduce the basic Efron result in the present study,the doubts raised about the minimum duration hypothesis by the reaction timedata and by the temporal order discrimination data, and the difficulties of recon-ciling the duration discrimination literature with the minimum duration hypo-thesis, suggest that the existence of a constant minimum perceptual duration hasno t yet been established. T h e relationship between the physical duration ofa stimulus and its perceptual duration is not yet understood and merits furtherinvestigation.

This research was supported by Grant A8260 from the National Research Council ofCanada. I would like to express my appreciation to A B. Kristofferson for his participationas a subject in this experiment, and for his insightful comments during dicusssions concernedconcerned with this research program.


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76 L. G . ALLANReferences

ALLAN,L. G. 1 9 6 8 ) . Visual position discrimination: a model relating temporal andspatial factors.

ALLAN,L. G. and KRISTOFFERSON,. B. 1974) . Psychophysical theories of duration dis-crimination.BRIGGS,G. G and KINSBOURNE, M 1972). Visual persistence as measured by reactiontime.EFRON, . 1 9 7 0 ~ ) . The relationship between the duration of a stimulus and the durationof a perception.EFRO N, . 197ob) . The minimum duration of a perception. Neuropsychologica, 8 57-63.EFRON,R. 1 9 7 0 ~ ) . Effect of stimulus duration on perceptual onset and offset latencies.

EFRON,R. 1 9 7 o d ) . The measurement of perceptual durations. Studium Generale ,EFRON, . 1 9 7 3 ) . An invariant characteristic of perceptual systems in the time domain.

Pp. 713-36. New York:Direct estimates of the apparent duration of a

Visual movement perception: a comparison ofPerception and Psychophysics, 8 ,Per-

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Temporal discrimination as a function of totalRevised manuscript received 10 ebruary 1975

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Quarterly Journal of Experime ntal Psychology, 24 3 8-25.Neuropsychologica, 8 , 37-55.

Perception and Psychophysics, 8 , 23 I .23 5-61.In KORNBLUM,. (Ed.), Attention and Performance IV.Academic Press.flash.sensitivity to vertical and horizontal movement.399-405.ception and Psychopliyysics, 2, 219-29.and Psychophysics, 13 81-3.ington), 182, 90-1000.presentation time.

HABE R, . N. and STANDING,. G. 1970) .KINCHL A, . A. and ALLAN, . G. 1970).Canad ian Journal of Psychology, 24 216-29.

KINCHLA, . A. and S M Y Z E R ,F. 1967).ROBINSON,. E. 1 9 7 3 ) .SWETS, A. 1 9 7 3 ) .THOR,. H . and S P I T Z ,H. H. 1968) .

A diffusion model of perceptual memory.Reaction time to the offset of brief auditory stimuli.

The relative operating characteristic in psychology.

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Allan - Is There a Constant Minimum Perceptual Duration!

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