Table 1.

Clarification of our terminology

Terms	How the terms are used in this article	Species-specific aspects
		Animals	Humans
Emotion primitives	Functional and adaptive properties, such as approach or avoidance behaviors which are observable, and which are expressions of internal brain (or emotion) states	Simple organisms can show emotion primitives as these have clear survival functions	Also humans can have emotion primitives
Survival functions	A subcortical defensive survival circuit centered on the amygdala which initiates defensive behaviors in response to threats	Present in all vertebrates
Emotions	Emotions are “bioregulatory reactions” that prepare the organism for adaptive behavior. They can exist without feelings and are unconsciously influencing behavior more than we think, and possibly more so than feelings do	Via observation of the expressions or by taking physiological measures, animal emotions can be inferred	Without being aware of it, emotions can have a large impact on humans behavior and decisions
Feelings	Feelings are the mental representations or cognitive interpretations of the physiological changes that occur during an emotion	We suggest experiential similarity between related species, but for the moment animal feelings remain inaccessible	Generally seen as what people verbally report as their subjective experience of emotion, although, for reasons outlined in the text, this may not be accurate
Evolutionary parsimony	When related species show similar behavior under similar circumstances, this is likely driven by similar psychological processes	A difficulty is that there is no hard line or golden standard that states when species are closely related enough
Cognitive parsimony	The simplest possible cognitive process should be assigned to observed behaviors	This is applied most often when interpreting the behavior of nonhuman animals	This is seldomly applied when interpreting human behavior