Rains of other organisms (129). Experiences we label and talk about as fear are not directly tied to the circuits that detect and respond to threats (see Nonconscious Conditioned Fear in Humans), and are not reliably correlated with body responses elicited by threats (130). Claims by some that animals must have conscious feelings because of the continuity of behavior across species (61?6) assume that behavior and conscious feelings are coupled in the brain. However, if this not the case, and it does not NS-018 cost appear to be, we cannot use information about defense responses to tell us whether animals are experiencing fear. Lloyd Morgan long ago warned against “humanizing the brute,” arguing that just because scientists necessarily start their exploration of animal behavior from their own subjective experiences does not justify the attribution of similar experiences to other animals (131). This kind of attribution is desirable, he says, when we interact socially with other humans but questionable when trying to understand animal behavior. Assumptions about unobservable subjective states are more complex than the assumptions about unobservable entities of physics or astronomy (128, 132).2874 | www.pnas.org/cgi/doi/10.1073/pnas.I am not proposing that animals lack conscious feelings. I just do not think that this is an issue that can be resolved scientifically, as Tinbergen also implied in the opening quote. We are on safe ground when we compare observable RWJ 64809MedChemExpress SB 203580 variables across species (defense responses elicited by threats). We can also be confident when we assume unobservable variables (feelings of fear) in other people, because all people have brains with the same functions and because we can compare notes with each other verbally. However, whether other animals feel fear when threatened is another matter. Different species have different brains, and even when the same brain areas and circuits are present, these do not necessarily perform the same exact functions. Also, as we have seen, responses elicited by threats are not telltale signs of fear, even in humans. Nevertheless, as I discuss below, we can learn quite a bit that is relevant to human feelings from studies of animals without making any assumptions about consciousness. Some will surely counter that this is too limiting. However, if we do not limit the discussion, confusion inevitably results. Those who observe our field lose track of what we are studying and what it means and are left to draw their own conclusions, which are understandably based on their everyday understanding of fear. Going forward, we need clear terms and concepts to advance the field. Coming to Terms with Fear There is a really simple solution to these problems. We should reserve the term fear for its everyday or default meaning (the meaning that the term fear compels in all of us–the feeling of being afraid), and we should rename the procedure and brain process we now call fear conditioning. So what should fear conditioning be called? There are two viable options. Pavlov’s original term, “defense conditioning,” is one. This expression reflected Pavlov’s focus on stimulus substitution–transfer of control of the defensive reflex from the US to the CS. Whereas the CS does come to control defensive freezing, this is not the same response elicited by the US–the US elicits jumping, flight, and other responses (9, 51, 57). Pavlovian aversive conditioning instead is more appropriately conceived of as involving a process in.Rains of other organisms (129). Experiences we label and talk about as fear are not directly tied to the circuits that detect and respond to threats (see Nonconscious Conditioned Fear in Humans), and are not reliably correlated with body responses elicited by threats (130). Claims by some that animals must have conscious feelings because of the continuity of behavior across species (61?6) assume that behavior and conscious feelings are coupled in the brain. However, if this not the case, and it does not appear to be, we cannot use information about defense responses to tell us whether animals are experiencing fear. Lloyd Morgan long ago warned against “humanizing the brute,” arguing that just because scientists necessarily start their exploration of animal behavior from their own subjective experiences does not justify the attribution of similar experiences to other animals (131). This kind of attribution is desirable, he says, when we interact socially with other humans but questionable when trying to understand animal behavior. Assumptions about unobservable subjective states are more complex than the assumptions about unobservable entities of physics or astronomy (128, 132).2874 | www.pnas.org/cgi/doi/10.1073/pnas.I am not proposing that animals lack conscious feelings. I just do not think that this is an issue that can be resolved scientifically, as Tinbergen also implied in the opening quote. We are on safe ground when we compare observable variables across species (defense responses elicited by threats). We can also be confident when we assume unobservable variables (feelings of fear) in other people, because all people have brains with the same functions and because we can compare notes with each other verbally. However, whether other animals feel fear when threatened is another matter. Different species have different brains, and even when the same brain areas and circuits are present, these do not necessarily perform the same exact functions. Also, as we have seen, responses elicited by threats are not telltale signs of fear, even in humans. Nevertheless, as I discuss below, we can learn quite a bit that is relevant to human feelings from studies of animals without making any assumptions about consciousness. Some will surely counter that this is too limiting. However, if we do not limit the discussion, confusion inevitably results. Those who observe our field lose track of what we are studying and what it means and are left to draw their own conclusions, which are understandably based on their everyday understanding of fear. Going forward, we need clear terms and concepts to advance the field. Coming to Terms with Fear There is a really simple solution to these problems. We should reserve the term fear for its everyday or default meaning (the meaning that the term fear compels in all of us–the feeling of being afraid), and we should rename the procedure and brain process we now call fear conditioning. So what should fear conditioning be called? There are two viable options. Pavlov’s original term, “defense conditioning,” is one. This expression reflected Pavlov’s focus on stimulus substitution–transfer of control of the defensive reflex from the US to the CS. Whereas the CS does come to control defensive freezing, this is not the same response elicited by the US–the US elicits jumping, flight, and other responses (9, 51, 57). Pavlovian aversive conditioning instead is more appropriately conceived of as involving a process in.
