We talking animals have a unique perspective on what it means to be sentient. For us, any nonverbal awareness is always already implicitly informed by our linguistic abilities. We don’t have to mentally say words to ourselves; language-based understanding unconsciously permeates our elementary perceptions of things.
Nonetheless we share nonlinguistic perception with all animals, and also share emotion and Aristotelian “imagination” with many of them. This kind of “imagination” is an organic production and experiencing of “images” that can play a role somewhat analogous to that of thought based on language in shaping responses to things. I won’t worry for now exactly what an “image” is. Animals clearly anticipate events and consequences that are not immediately present to sensation, based on some kind of experiential learning. This seems to be related to what some of the Latin scholastics tried to explain in terms “natural signification”.
The most obvious interpretation of this kind of imagination is by a kind of analogy with sensation. We and other animals remember sensations that are no longer present, and imaginatively anticipate sensations in advance. This seems to imply somehow imagining certain things to be true, but without any explicit discursive reasoning. What is truth for my puppy?
I think emotion may be a big part of the answer. Emotion is in part a kind of spontaneous valuation of things. Specialists in human social psychology have found that simple emotional valuations of different things are surprisingly good statistical predictors of what ways of combining them people will regard as realistic or unrealistic, or true or false. I’m inclined to speculate that many animals live mainly by this kind of emotionally based valuation and classification (see also Ethos, Hexis; Parts of the Soul; Reasonableness; Feeling; Emotional Intelligence; Aristotle on the Soul; Aristotelian Subjectivity Revisited; Vibrant Matter).