 Psychologists have recently begun studying event perception and its neural basis (e.g., Zacks and Tversky 2001; Zacks, Tversky, and Iyer 2001; Zacks et al. 2006). The underlying question behind this line of research is whether events play a role in how we cognitively structure and remember changing states of affairs and how they are represented. Zacks, Tversky, and Iyer (2001) use an analogy from the domain of objects to the domain of events to define an event as a “segment in time at a given location that is conceived by an observer to have a beginning and an end” (p.30). They claim that “the ability to identify the parts of events and their relationships constitutes a distinct perceptual process” (p.30) which they call event structure perception. Just as an object is an ontological primitive in the spatial domain, so an event is an ontological primitive in the spatio-temporal  domain.[9]  Objects are recognized by shape, color etc. and have boundaries in space. Analogously, events have boundaries in time, but are also bounded in space. An event of buttering toast, for instance, happens at a particular time, but also in a particular location in space and is therefore spatially bounded. Continuing the analogy, both objects and events can be identified and categorized using hierarchical relations. 