Hoerl & McCormack's (H&M's) model of temporal cognition is based on two parallel systems: (1) a primary system available to any sentient creature (i.e., the updating system) and (2) a cognitive-based system available only to humans (the reasoning system). Furthermore, according to the model, the reasoning system would be accessible only to children from about the age of 3 years, although this access would remain partial until the age of about 5 years. However, the model did not mention the potential implication of emotion in either of these systems. Therefore, we try to broach how emotion could affect these two systems separately among humans (because the literature on the emotional interference in time perception is scarce among animal studies).

According to the model, the updating system would include a simple timer accessible to any creature, allowing them to measure duration between two events, or to monitor time passing by after a specific event. This timer appears to fit the timing mechanism – the scalar expectancy model – proposed by Gibbon et al. (Reference Gibbon, Church and Meck1984), which was first validated among animals, and further supports the validity of this timer mechanism in the model. According to this timer model, a pacemaker-like mechanism emits pulses, which are recorded in an accumulator, the emission starting at the beginning of an interval and finishing at the end of it. The accumulated pulses are then compared to previously stored pulses, facilitating decision-making. Interestingly, a modification of this model, the attentional gate model (AGM) (Zakay Reference Zakay2000) accounts for the emotional interference. According to the AGM, two potential processes would be at stake in the presence of emotional stimuli: an attentional effect and an arousal effect. The attentional effect could either redirect the attention of the individual on time (i.e., as the individual “avoids” the emotional stimuli) or distract the individual from time (i.e., as the individual is “attracted” by the emotional stimuli). In this case, the individual could either underestimate the duration (i.e., as she or he records fewer pulses as a result of distraction) or overestimate the duration (i.e., as he or she records more pulses as a result of their increased attention towards time). In relation to the arousal effect, the effect would be uniform across the situations because the arousal would lead to an increase in the pulse rate, thereby leading to an overestimation of the duration.

Concerning the model's reasoning systems, the explanation of emotional interference is more complex because this system regroups several distinct processes governing temporal cognition. Briefly, this system, compared with the updating one, is supposed to include information about the world not only as it is in the present, but also as it was in the past and may be in the future. Therefore, a creature able to use this system should be able to order events that occurred in the past, plan a future task in the correct order, and discriminate the recency of past events. Although the literature on these specific processes is scarce, research tends to point toward a disruptive effect of emotion, diminishing the ability for one to use this system. Indeed, Huntjens et al. (Reference Huntjens, Wessel, Postma, van Wees-Cieraad and de Jong2015) showed that when presented with highly arousing pictures depicting a story (i.e., either positively or negatively valenced), participants had a harder time ordering them in chronological order. Furthermore, it has been found that experiencing a traumatic event can lead to a disrupted narrative of the event (e.g., among abused children; see Miragoli et al. Reference Miragoli, Camisasca and Di Blasio2017), which is supported by studies showing a disruptive effect of negative emotions on episodic memory (Bisby et al. Reference Bisby, Horner, Bush and Burgess2018). Furthermore, traumatic events would tend to bias the temporal order of the event preceding and following the event itself (Byrne et al. Reference Byrne, Hyman and Scott2001).

Interestingly, the separation between the updating and reasoning systems is relatively close to the separation between absolute and relative dating (Shimojima Reference Shimojima2002). Absolute dating is when an individual uses the stored memorised date of an event to judge how much time has passed since the event, whereas the subjective timing refers to an approximation made without the use of the exact date. Shimojima (Reference Shimojima2002) demonstrated that although his participants knew the exact date of an event, and therefore the exact time that had since passed, they felt subjectively more or less time had passed since that event, indicating a discrepancy between the absolute and relative dating. Furthermore, Shimojima (Reference Shimojima2004) also demonstrated that emotionally charged events (i.e., whether negatively or positively valenced) would lead to discrepancies between absolute and relative dating, further supporting the disruptive effect of emotion. It is noteworthy that H&M's model mentions that discrepancies have been observed between the reasoning and updating systems, which could be supported by Shimojima's study (2004). These assumptions are also partially supported by the effect of emotion on episodic memory because it has consistently been reported that emotional events (Bowen et al. Reference Bowen, Kark and Kensinger2018; Kuriyama et al. Reference Kuriyama, Soshi, Fujii and Kim2010; Phelps & Sharot Reference Phelps and Sharot2008), as well as the spatiotemporal context of these events (Schmidt et al. Reference Schmidt, Patnaik and Kensinger2011), are more vividly remembered. Therefore, the absolute dating of such emotional events would be highly precise (i.e., the context being remembered more intensely), whereas relative dating would suffer from the telescoping effect (i.e., the tendency to underestimate the time passed since a distant memory; see Shimojima & Koyazu Reference Shimojima and Koyazu1999; Thompson et al.Reference Thompson, Skowronski and Lee1988), leading to a discrepancy between the two types of dating (i.e., resembling the discrepancies broached in H&M's model).

In this commentary, we have demonstrated that emotion could be incorporated as a major variable in H&M's model. The research outlined appears to fit in almost seamlessly for both systems in the model, although further research is required to fully explain how emotion and the reasoning system interact. Interestingly, the interaction between emotion and temporal cognition provides more explanation of the model's discrepancies between the two systems.