Temporal Grouping

Time perception is articulated into structures in the strict sense of the term. Perceived elements are arranged in an orderly fashion by grouping factors, and this provides evidence that time perception does not consist solely in locating events according to their before/after succession in physical time. The early study of temporal grouping factors is Bozzi and Vicario (1960) (cf. Deutsch, 2013). A sequence of four pure tones is presented, for instance C₄ (262 Hz), B₅ (988Hz), C # ₄ (277 Hz) and C₆ (1046 Hz), which are cyclically alternat­ed without any pause between them. If each tone’s duration amounts to 200 msec., a single succession of alternating higher and lower tones is perceived. If duration is diminished to 50 msec., one hears two clear-cut distinguished tonal lines that are distant in the tonal space. The higher-pitched tones are grouped together in a tonal line that gives rise to a high-pitched trill. The lower-pitched tones are grouped together in a tonal line that gives rise to a low-pitched trill. Trills are perceived as simultaneous sounds that develop independently of and stand out against each other. This shows that phenomenal time is a form of qualitative ordering of events. At optimally short durations, the grouping fac­tor of temporal proximity is replaced by the factor of tonal proximity. Thus the one-dimensional order of the succession is changed into the ordering of tones into two parallel tonal lines. It is noteworthy that the tonal lines preserve the nature of perceptual objects in general, that is, their phenomenal continuity. Trills are smooth and unitary. It is impossible to hear the pauses between the tones of each line that should correspond to the places left empty in the suc­cession by the tones grouped in either one of the trills (this phenomenon is akin to what one perceives in the well-known “scale illusion,” cf. Deutsch, 1975).

The evidence that time perception is founded on phenomenal structures accounts for the acoustic tunnel effect and the amodal completion in time (Vicario, 1960, 1980). If a sound, for instance a tone, a piece of a melody or a spoken fragment, is presented for at least 1-2 seconds, then is replaced by a noise for 200-700 msec., and then by another sound that is qualitatively iden­tical to the first for 1-2 seconds, subjects hear one and the same sound that persists through the noise, which is heard as a momentary disturbance some­how covering the sound. The sound is so perceptually present as a complete auditory object that it appears partially occluded by the noise, while subjects hardly believe that the noise does not actually contain the sound. Of course there are conditions necessary for this phenomenon to occur. The noise must differ from the sounds by at least 40 dB, otherwise it does not appear as a tun­nel through which sound passes and subjects hear first a sound, then an inter­ruption due to the noise and at last a new sound. The noise must not extend below 0.1 or beyond 0.7 sec. If the noise is too short, it cannot cover the sound that is perceived as if it were wholly present, while the noise is localized else­where. If it is too long, there is no continuation or completion of the sound. It is stopped by the noise, at whose end it is heard to start again.

This phenomenon has a specific temporal extent that functions as a kind of inherent feature for it to occur. It is equivalent to the greatest duration of the noise that allows for the completion of sound behind it, which amounts to 1.2 sec. This temporal feature is optimal if the first and second sounds do not last fewer than 100 msec. Given this time value, the temporal structure induces subjects to connect the sounds that differ more in pitch from the first, so that the phenomenon does not take place.

Source: Calì Carmelo (2017), Phenomenology of Perception: Theories and Experimental Evidence, Brill.