Mahr & Csibra's (M&C's) proposed communicative function of episodic memory as a tool for discourse and for memory accuracy detection in others is a novel contribution to our understanding of the function of episodic memory. However, the original function of episodic memory is to enhance personal survival, only part of which can be understood with regard to interpersonal function. Although humans are inherently social, and the ability to gain trust and interpret the trustworthiness of others is certainly important to our survival, we suggest that the emotional modulation on the episodic memory system, specifically related to appraising the significance of events to the self, developed to navigate first the physical and then the social world.

Episodic memory changes as a function of self-centered appraisals, which derive from personal significance and drive emotional experience. M&C suggest that our ability to encode rich, detailed descriptions of an event function as a way to provide evidence to others of the veridical nature of our memories. However, the vividness of events varies according to the way in which the memory was individually and idiosyncratically encoded. This is in part related to variation in genes' altering neurotransmitters regulating bodily sympathetic (e.g., blood pressure and heart rate) and neural stress-arousal systems. We have shown that the ADRA2b polymorphism regulates the experience of arousal during encoding, determining first what is likely to be attended and perceived and only then later remembered (Todd et al. Reference Todd, Müller, Lee, Robertson, Eaton, Freeman, Palombo, Levine and Anderson2013; Reference Todd, Ehlers, Müller, Robertson, Palombo, Freeman, Levine and Anderson2015).

The expression of these genetic arousal modulatory influences on episodic memory also interact with specific emotional appraisals and defensive and appetitive reactions. Emotional arousal increases vividness of recollection; specifically, negative emotional arousal is associated with greater detail in recognition memory, and positive emotional arousal at encoding results in greater recollective memory (Gomes et al. Reference Gomes, Brainerd and Stein2013). Yet when arousal is controlled, negatively valenced stimuli increases gist memory (Bookbinder & Brainerd Reference Bookbinder and Brainerd2017) – episodic memory, therefore, is altered later on as a function of an individual's internal state and interpretation of stimuli at the moment of encoding. Within negatively valenced responses, disgust appears to have a stronger grip on attention and memory than anxiety (Chapman et al. Reference Chapman, Johannes, Poppenk, Moscovitch and Anderson2013). The specific and varied influence of emotional states and appraisals at encoding clearly change the nature and strength of memory. Each of us wear genetic and emotional experiential lenses that filter experience in unique ways to modulate the character of episodic memory. Whereas some of us may remember for the sake of benefits to others, many of us remember to save our bodies and ourselves.

Encoding of events in relation to the self, and specifically in relation to survival, even without elevated emotional arousal, has potent influences on episodic memory. Irrespective of emotional state, the appraisals an individual utilizes, whether related to meaning or self-relevance, alters the magnitude and quality of their recall. These may originate from life-or-death appraisals. Indeed, the central tenet of adaptive memory is that our memory systems evolved with a preference for fitness-related information, demonstrating that episodic events related to our survival are associated with greater recall than other episodic events (Nairne et al. Reference Nairne, Thompson and Pandeirada2007). The prevalence of false memories varies in a similar way. Negative emotional memories, as well as neutral events processed in relation to one's survival (Otgaar & Smeets Reference Otgaar and Smeets2010), are associated with higher vividness and higher rates of false memory (Brainerd et al. Reference Brainerd, Stein, Silveira, Rohenkohl and Reyna2008). False memory does not occur only in situations where one is to serve as witness or is engaged in discourse to aid in collective memory, as would be expected by M&C's characterization of episodic memory.

ADRA2b polymorphisms regulating brain norepinephrine extends beyond individual differences in emotional arousal and healthy memory to the formation of traumatic memories and posttraumatic stress disorder (Todd et al. Reference Todd, Palombo, Müller, Robertson, Eaton, Freeman, Levine and Anderson2014). Biological predispositions in conjunction with traumatic experience can alter how one sees, appraises, and remembers the world. People who have experienced traumatic events differ in their views of self and world based on how they appraised the event at encoding (Sutherland & Bryant Reference Sutherland and Bryant2008). Internal appraisals of situations alter an individual's beliefs about past events and self-concept in lasting ways that hold true over time (Startup et al. Reference Startup, Makgekgenene and Webster2007). Critically, these shifts in viewpoint are also often associated with a reduction in interpersonal interaction and discourse (e.g., McFarlane & Bookless Reference McFarlane and Bookless2001). The nature of intrusive memories following trauma is inherently personal; in its vivid re-experiencing, it is common for people with posttraumatic stress disorder to be uncomfortable discussing these experiences with others (e.g., Cook et al. Reference Cook, Riggs, Thompson, Coyne and Sheikh2004). Vivid recollection in trauma is associated with sharing less, not more, limiting what is transmitted collectively.

Although highly emotional and traumatic experiences may reflect a broken episodic memory system, they might also serve to illuminate the origins of episodic memory. What we have learned from the neurogenetics of emotions and traumatic memory is that episodic memory likely originates first in preserving the integrity of one's physical body, and that has expanded to include the mental self. Only thereafter may it have been co-opted broadly for the purposes of preserving the fabric of the collective social self.