In Livewired, David Eagleman proposes that the sensitivity of living beings is essentially the transformation of environmental information into patterns of neural activity, from which the sensation of perception emerges. The nature of the original stimulus is irrelevant; what matters is that it can be decoded by the nervous system that receives it, providing meaningful information about the environment. Natural selection would favor individuals who develop sensory organs specialized in capturing the most relevant information from a particular habitat, allowing them to interact more efficiently with their surroundings, thereby increasing their chances of survival and reproduction. This, in turn, would lead to the gradual refinement of these organs over successive generations.
This process has led to the development of a wide array of sensory organs—or, as Eagleman calls them, peripheral devices. For instance, bats have evolved the ability to detect the shape of their environment through the perception of echoes from sounds they emit themselves, enabling them to thrive in low-visibility environments such as caves. In aquatic environments, certain predators like sharks can detect the electric fields generated by their prey, aiding in their capture. Migratory birds, on the other hand, can—through mechanisms not yet fully understood—perceive Earth’s magnetic field as a kind of natural compass to navigate during long-distance travel in search of food or mates.
As we can see, the variety of sensory receptors found in nature is fascinating. However, these are only the foundation of perception.
Isolated sensory information has very limited utility. Take, for example, the sound your front door makes when it opens. It certainly conveys information, but depending on the context in which this auditory stimulus is perceived, its meaning can vary dramatically, and so will the response to it, which ultimately determines how effectively we interact with our environment. If you hear it at the time your partner usually comes home from work, you will feel and react very differently than if you hear it at 3 a.m. when no one is expected. It is this context that completes the meaning of the stimulus, shaping the subjective experience it evokes and modifying the resulting behavior. In this example, the contextual cue is the time of day, but many contextual factors can alter the meaning (and therefore the subjective perception and response) of an isolated sensory input. Some of these include culture, past experiences, expectations, and the emotional state of the perceiver.
The famous experiment with Pavlov’s dogs illustrates that, beyond humans, other animal species also use context to assign meaning to isolated stimuli. However, given that the human brain is the most complex organ observed in nature, it stands to reason that the sophistication of such influences is far greater in humans than in other species. This results in highly modulated perceptions shaped by subjective, social, and symbolic factors that go far beyond the physical properties of the stimulus.
We now invite you to try a simple exercise to illustrate the complexity and importance of contextual influence on perception. Listen to this piece by pianist and composer Ludovico Einaudi together with a group of friends and/or family:
What did each of you feel?
It is very likely that this auditory stimulus triggered different emotions in each listener. Perhaps someone became emotional remembering a scene from a film in which this piece served as the soundtrack. Someone learning to play the piano might have felt admiration for the complexity of the composition. Another person might have felt sadness, recalling a deceased loved one who enjoyed the song. Someone feeling stressed by work might have remained indifferent, preoccupied with unfinished tasks instead of focusing on the music. Many possibilities exist, but what is certain is that individual context modified perception.
Understanding that all sensory perception is influenced by context encourages us to view subjective clinical phenomena—such as pain or fatigue—from a different perspective. As healthcare professionals, it is essential to consider the patient’s emotional, social, and cognitive environment to better understand how symptoms are experienced and expressed. Moreover, identifying contextual elements that can be modified opens up the possibility of using them as therapeutic tools.
One of the research lines of the UMSS group focuses on deepening our understanding of the influence of these contextual factors in patients with chronic conditions. We hope to contribute to scientific progress and to the dissemination of this knowledge.
References:
1. David Eagleman [Internet]. 2019 [citado 12 de mayo de 2025]. Livewired. Disponible en: https://eagleman.com/books/livewired/
2. Rehman I, Mahabadi N, Sanvictores T, Rehman CI. Classical Conditioning. En: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 [citado 12 de mayo de 2025]. Disponible en: http://www.ncbi.nlm.nih.gov/books/NBK470326/