How do these different magnitudes interact? From a theoretical perspective, Meck and Church (
1983) proposed the “mode control” model, uniting number and time processing (Gibbon, Church, & Meck,
1984; Meck, Church, & Gibbon,
1985). This model proposes that number and time are represented by an internal clock that consists of “pacemaker”-type pulses which accumulate in a counter. Based on this model, number and duration discrimination rely on a single magnitude system which operates in either the counting or the timing mode (Fetterman,
1993). From an experimental perspective, a number of behavioral (Alards-Tomalin, Walker, Kravetz, & Leboe-McGowan,
2016; Cappelletti, Freeman, & Butterworth,
2011; Cappelletti et al.,
2009; Chun, Lee, Lee, & Cho,
2018; Dormal, Seron, & Pesenti,
2006; Gilaie-Dotan, Rees, Butterworth, & Cappelletti,
2014; Javadi & Aichelburg,
2012; Lambrechts, Walsh, & Van Wassenhove,
2013; Martin, Wiener, & Van Wassenhove,
2017; Tokita & Ishiguchi,
2011; Tsouli, Dumoulin, te Pas, & van der Smagt,
2019) and neuroimaging (Bueti & Walsh,
2009; Cappelletti et al.,
2014; Castelli, Glaser, & Butterworth,
2006; Hayashi et al.,
2013; Javadi, Brunec, Walsh, Penny, & Spiers,
2014) studies provide support for a partly shared processing system for numerosity and time, whereas other studies suggest that numerosity and time are independent and are processed by distinct mechanisms (Agrillo, Piffer, & Adriano,
2013; Agrillo, Ranpura, & Butterworth,
2010).