Mather et al. beautifully describe the neuronal mechanisms likely to account for an arousal-based modulation of selectivity phenomena in attention and memory. In addition to previous emotion–cognition models focusing on the competition between emotional and neutral stimuli, the GANE (glutamate amplifies noradrenergic effects) model also aims to explain how arousal resolves the competition between neutral stimuli. In this context, I propose a complementary perspective.

I argue that the GANE model explains mainly the mechanisms underlying the processing of emotional stimuli, whereas co-occurring effects on the processing of neutral stimuli may be interpreted as side effects of a contextualization process targeting the emotional stimulus. The empirical evidence Mather and colleagues present suggests that arousal-based amplification or inhibition of neutral input is heavily constrained by the spatiotemporal relationship between an emotional stimulus, which is the driving source of arousal, and neutral stimuli constituting the sensory context. I claim that effects of emotional stimuli on proximal neutral ones are a signature of stimulus contextualization in favor of a disambiguation of emotional stimuli. Indeed, for the perceiving agent, emotional stimuli are often characterized by significant ambiguity (cf. Duval et al. Reference Duval, Moser, Huppert and Simons2013). For example, the recognition of an arousing facial expression may be context dependent (cf. Barrett et al. Reference Barrett, Mesquita and Gendron2011).

The valence and the discrete emotional category of an arousing stimulus are not completely inherent features of the stimulus, but they are also constituted by the context (including neutral stimuli) in which the arousing stimulus is embedded. Therefore, the processing of an emotional stimulus benefits from an amplification of salient neutral stimuli standing in an optimal spatiotemporal relationship to the emotional target stimulus. It appears beneficial for the human organism that emotional stimuli are not processed in isolation from rather neutral context information. Amplifying the processing of otherwise prioritized neutral stimuli in the presence of an emotional stimulus creates a context that facilitates the appropriate classification and encoding of the properties of the emotional stimulus. Indeed, the context seems to be routinely encoded during emotion perception (Barrett & Kensinger Reference Barrett and Kensinger2010). In this sense, the arousal-based mechanisms outlined in the GANE model cannot be generalized to settings in which emotional stimulation is rather negligible. However, based on this perspective, two aspects may help to further improve the conceptual framework of the model and its validity:

First, I propose that the GANE model would benefit from a more explicit distinction between internally and externally located sources of emotional arousal (cf. Kaspar Reference Kaspar2013; Kaspar & König Reference Kaspar and König2012). The current model addresses primarily the latter type, namely, sensory stimuli located outside of the perceiving agent, whereas internal forms of emotional arousal refer to the agent's current emotional/mood state. While the arousing power of external stimuli is tied to the stimuli and, hence, places tight spatiotemporal constraints for an amplification or inhibition of the neutral surrounding, arousal elicited and maintained by internal thoughts of the agent might be more easily linked to any neutral stimulus. Of course, an internally located source of emotional arousal might be elicited by an external source, but some residual arousal (i.e., mood) continues for a while after source offset. Indeed, excitation-transfer theories (Bryant & Miron Reference Bryant, Miron, Bryant, Roskos-Ewoldsen and Cantor2003; Zillmann Reference Zillmann, Cacioppo and Petty1983) propose that the residual arousal from a stimulus can be transferred to a subsequent stimulus, whereas the emotional valence of the stimuli may differ. If residual arousal can actually be tapped by a stimulus other than the original in this way (still to be shown), we can extend the validity of the GANE model by implementing a multisource approach to arousal-biased information processing.

Second, the model neglects the valence aspect of arousing sources being of central relevance, not only from the perspective of disambiguation tendencies. It seems that the arousal and valence ascribed to a stimulus are not completely independent features (cf. Kaspar & König Reference Kaspar and König2012), whereby negative (vs. positive) stimuli show a tendency toward higher arousal (Ito et al. Reference Ito, Cacioppo and Lang1998; Kim & Hamann Reference Kim and Hamann2007). Thus, negative stimuli may have a higher potential to ignite neuronal hotspots and to fine-tune priority signals. This bias is plausible from an evolutionary perspective, as it is more prejudicial to miss a potential threat than to miss a potential reward. Thus, across different scenarios, external negative (vs. positive) stimuli may elicit stronger modulation effects on neutral stimuli being in an optimal spatiotemporal distance, whereas a negative (vs. positive) mood state might have more long-lasting effects because of more residual excitation.

Indeed, the location (internal vs. external) and valence of the arousing source have a critical influence on attention and memory processes. For example, younger adults showed an attentional preference and better memory performance for negative stimuli compared with positive stimuli, and this bias was more pronounced when participants had been in a positive (vs. negative) mood (Kaspar et al. Reference Kaspar, Ramos Gameiro and König2015). Thus, internal and external sources of emotional arousal may show specific interactions depending on their valence. With respect to the GANE model, negative stimuli presumably have a higher likelihood to bias perception and memory when they are in strong contrast to emotional background noise within the perceiving agent. However, preferences for positive over negative information have also been reported for younger adults in specific circumstances (Becker & Leinenger Reference Becker and Leinenger2011; Parrott & Sabini Reference Parrott and Sabini1990; Schwager & Rothermund Reference Schwager and Rothermund2013), indicating more complex mechanisms of the processing of emotion-laden stimuli than delineated in an exclusive arousal-based model.

Finally, in this context, the GANE model suggests a brain-based explanation for the very reliable information processing bias toward positive (vs. negative) information in older adults (Reed et al. Reference Reed, Chan and Mikels2014). Mather and colleagues proposed that arousal may not increase selectivity similarly effectively among older adults because of age-related changes in the locus coeruleus–norepinephrine system. If so, negatively valenced stimuli may gradually lose their high arousing potential across the life span, facilitating controlled attentional shifts toward positive stimuli at an older age (cf. Hahn et al. Reference Hahn, Carlson, Singer and Gronlund2006; Knight et al. Reference Knight, Seymour, Gaunt, Baker, Nesmith and Mather2007). Thus, the GANE model adds a brain-based explanation for this age-dependent change in biased competition that is discussed mainly in terms of the socioemotional selectivity theory (Carstensen et al. Reference Carstensen, Fung and Charles2003) emphasizing age-related changes in emotion-regulation motivation.