title: Capacity limit of simultaneous temporal processing: how many concurrent 'clocks' in vision?
abstract: A fundamental ability for humans is to monitor and process multiple temporal events that occur at different spatial locations simultaneously. A great number of studies have demonstrated simultaneous temporal processing (STP) in human and animal participants, i.e., multiple 'clocks' rather than a single 'clock'. However, to date, we still have no knowledge about the exact limitation of the STP in vision. Here we provide the first experimental measurement to this critical parameter in human vision by using two novel and complementary paradigms. The first paradigm combines merits of a temporal oddball-detection task and a capacity measurement widely used in the studies of visual working memory to quantify the capacity of STP (CSTP). The second paradigm uses a two-interval temporal comparison task with various encoded spatial locations involved in the standard temporal intervals to rule out an alternative, 'object individuation'-based, account of CSTP, which is measured by the first paradigm. Our results of both paradigms indicate consistently that the capacity limit of simultaneous temporal processing in vision is around 3 to 4 spatial locations. Moreover, the binding of the 'local clock' and its specific location is undermined by bottom-up competition of spatial attention, indicating that the time-space binding is resource-consuming. Our finding that the capacity of STP is not constrained by the capacity of visual working memory (VWM) supports the idea that the representations of STP are likely stored and operated in units different from those of VWM. A second paradigm confirms further that the limited number of location-bound 'local clocks' are activated and maintained during a time window of several hundreds milliseconds.
authors.affiliation: Key Laboratory of Adolescent Cyberpsychology and Behavior (CCNU), Ministry of Education, Wuhan, China; School of Psychology, Central China Normal University, Wuhan, China; Key Laboratory of Human Development and Mental Health of Hubei Province, Wuhan, China.
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Key Laboratory of Adolescent Cyberpsychology and Behavior (CCNU), Ministry of Education, Wuhan, China; School of Psychology, Central China Normal University, Wuhan, China; Key Laboratory of Human Development and Mental Health of Hubei Province, Wuhan, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Yang
authors.affiliation: Key Laboratory of Adolescent Cyberpsychology and Behavior (CCNU), Ministry of Education, Wuhan, China; School of Psychology, Central China Normal University, Wuhan, China; Key Laboratory of Human Development and Mental Health of Hubei Province, Wuhan, China.
authors.forename: Yaqian
authors.initials: Y
authors.lastname: Han
authors.affiliation: Key Laboratory of Adolescent Cyberpsychology and Behavior (CCNU), Ministry of Education, Wuhan, China; School of Psychology, Central China Normal University, Wuhan, China; Key Laboratory of Human Development and Mental Health of Hubei Province, Wuhan, China.
authors.forename: Xianfeng
authors.initials: X
authors.lastname: Ding
authors.affiliation: Key Laboratory of Adolescent Cyberpsychology and Behavior (CCNU), Ministry of Education, Wuhan, China; School of Psychology, Central China Normal University, Wuhan, China; Key Laboratory of Human Development and Mental Health of Hubei Province, Wuhan, China.
authors.forename: Zhao
authors.initials: Z
authors.lastname: Fan
mesh_terms: D000293:Adolescent; D000328:Adult; D001921:Brain / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008570:Memory, Short-Term; D008606:Mental Processes / Q000502:physiology*; D055815:Young Adult