What's the science?
Subjective feelings are central to everyday human life from forgetfulness to feeling ill or having a good day with a friend. Subjective feeling is the current subjective phenomenological state of an individual. We currently do not have a clear understanding of the organization of inner feelings and where they can be mapped in the body or brain, despite how subjective feelings underlie most aspects of everyday life. Recently in PNAS, Nummenmaa and colleagues generate a map of different subjective feelings using subjective reports of feelings, bodily sensations and neuroimaging data associated with these feelings.
How did they do it?
1026 participants were interviewed and rated 100 subjective “feeling states” ranging from physiological sensations like hunger, to emotional and cognitive feelings like a pleasurable experience or the feeling of trying to remember something. They rated the intensity of these feelings in 4 dimensions 1) the mental experience 2) the bodily sensations associated with these feelings 3) the emotional contribution and 4) the level of control they had associated with these feelings. Participants were shown tokens associated with feelings as a list on a screen and were asked to arrange these feeling states in a box based on their similarity to one another. They were then asked to color on an image of the body where they felt a particular feeling state. They authors assessed how similar these feelings were to one another, how they map out topographically and onto the body, and lastly whether they were associated with patterns of brain activity using neuroimaging data (NeuroSynth: a database of brain activity studies and their associated topics). They performed a “representational similarity analysis” to determine how similar these feeling, body and brain maps were to one another.
What did they find?
The intensity of the mental experiences and bodily sensations associated with subjective feeling states were highly correlated. Almost all subjective feelings were associated with emotion. Less control was felt for unpleasant feelings than for pleasant feelings and for bodily states than cognitive/ mental states. Based on the rating of similarity between feelings, the authors created topographical map of the mental feeling space. Used density-based clustering they found 5 distinct clusters which included positive emotion, negative emotion, cognitive states, somatic states/illnesses and homeostatic states. They then used t-distributed stochastic neighbor embedding to determine how these clusters differed in the 4 dimensions of feeling. Mental involvement and positive vs. negative valence of a feeling were the most important dimensions. Negative and positive emotions were both mapped highly on the vertical scale of mental intensity, demonstrating that the more intense the emotion, the more strongly it is experienced in the mind. On the horizontal scale of emotional intensity, positive and negative emotions mapped on opposite ends of the spectrum. Homeostatic states (like eating), illnesses and cognitive states (like reasoning) were lower on the scale of mental intensity, demonstrating that they are experienced to a weaker degree in the mind. Cognitive processes were mapped towards the positive end of the spectrum of emotion, while illnesses are experienced as negative. Greater control (agency) was felt over positive feelings and cognitive processes, while less control was felt over negative feelings and illnesses.
All feeling states were associated with distinct bodily sensation maps, even for cognitive processes like remembering or reasoning. This mapping of feeling state onto body regions also clustered in a similar way demonstrating a similar organization of feeling states in the body. Lastly, they found that the organization of bodily feeling was associated with the mapping of subjective feelings based on brain activation. This neural organization of feeling states was also associated with the semantic similarity (from words associated with brain activity recorded in the NeuroSynth database). This suggests that there are neural signatures of subjectively felt bodily states associated with feelings. The subjective experience of mental states, however, was not associated with patterns of brain activation.
What's the impact?
This is the first study to map subjective feelings in terms of their subjective experience, their bodily sensations and their location in the brain. We now know that subjective feelings cluster into different types of feelings and that these correspond to distinct maps on the body. These patterns of bodily sensation also map onto brain activity associated with particular feelings. Understanding how we feel things is important for everyday life and for understanding the human experience.
Nummenmaa et al., Maps of subjective feelings. PNAS (2018). Access the original scientific publication here.