Confronted daily by our screens, we frequently overlook sensory modalities beyond auditory and visual input. Nevertheless, these senses remain perpetually engaged. When we heighten our awareness, we discern the varied textures of objects, the muscular tension in our shoulders, or the delicate softness of freshly baked bread.
Upon waking, the invigorating sensation of toothpaste on our gums might be apparent, followed by the auditory and tactile experience of running water in the shower, the fragrant notes of shampoo, and subsequently, the enticing aroma of a freshly prepared coffee.
While Aristotle posited the existence of five primary senses, his cosmological views, which included the notion of the world being composed of five fundamental elements, are no longer accepted. Contemporary scientific inquiry suggests that humanity may possess a far greater number of sensory faculties, potentially numbering in the dozens.
The vast majority of our lived experience is inherently multisensory. Our perception is not compartmentalized into distinct visual, auditory, olfactory, and tactile streams. Instead, these sensory inputs converge simultaneously, contributing to a cohesive and unified apprehension of our environment and our internal state.
Our tactile perceptions can significantly influence our visual interpretations, just as visual cues can modulate our auditory processing. For instance, the olfactory profile of a shampoo can alter one’s perception of hair texture; the scent of roses, for example, can render hair subjectively silkier.
Similarly, the aroma of low-fat yogurts can enhance their perceived richness and viscosity on the palate, even without the addition of further emulsifying agents. The olfactory perceptions experienced within the oral cavity, subsequently rising to the nasal passages, are demonstrably influenced by the rheological properties of ingested liquids.
My long-standing research associate, Professor Charles Spence from Oxford’s Crossmodal Laboratory, has indicated that his neuroscientific counterparts estimate the number of human senses to be between twenty-two and thirty-three distinct modalities.
These encompass faculties such as proprioception, which grants us an awareness of our limbs’ spatial orientation without requiring visual confirmation. Our sense of equilibrium is also contingent upon the vestibular system located within the inner ear, in conjunction with visual input and proprioceptive signals.
Another notable sense is interoception, which allows us to register internal bodily signals, such as subtle elevations in heart rate or the sensation of hunger. We also possess a sense of agency, the feeling of actively controlling our movements, a perception that can be compromised in individuals who have experienced strokes, sometimes leading to the erroneous belief that their limbs are being moved by external forces.
Furthermore, there is the sense of ownership over one’s body parts. Stroke survivors may, in certain instances, experience a dissociation from their limbs, feeling as though they do not belong to them, despite the retention of sensory feedback.
Some of the conventionally recognized senses are, in fact, complex integrations of multiple sensory inputs. For example, the sensation of touch encompasses pain, temperature, pruritus (itch), and various tactile stimuli. When we engage in tasting, we are actually experiencing a confluence of three sensory modalities: touch, olfaction, and gustation (taste), which collectively contribute to the complex flavor profiles we perceive in foods and beverages.
Gustation inherently involves the detection of basic tastes such as saltiness, sweetness, sourness, bitterness, and umami (savory) via specialized receptors on the tongue. However, the perception of flavors like mint, mango, melon, strawberry, or raspberry presents a different scenario.
Our tongues are not equipped with specific receptors for raspberry, nor is raspberry flavor a simple amalgamation of sweet, sour, and bitter. The perception of fruit flavors does not adhere to a straightforward “taste algebra.”
These nuanced flavors are apprehended through the synergistic interplay between the tongue and the nasal passages. Crucially, it is olfaction that accounts for the predominant contribution to what we commonly refer to as taste.
This phenomenon does not pertain to the inhalation of ambient odors. Instead, volatile aromatic compounds are released during mastication or sipping, subsequently ascending from the oral cavity to the olfactory epithelium via the nasopharynx at the posterior aspect of the throat.
Tactile feedback also plays a critical role, serving to unify gustatory and olfactory sensations and to shape our predilections for specific textures, whether it be the preferred consistency of eggs or the decadent, yielding richness of chocolate.
Visual perception is demonstrably influenced by our vestibular system. Consider the experience of observing the interior of an aircraft cabin while the plane is stationary on the ground, and then again during its ascent.
The perception may shift, with the forward section of the cabin appearing elevated relative to your position during the climb. This visual distortion arises from the combined input of sight and the signals from your inner ear canals, which indicate a backward tilt. What you “see” is a construction informed by both visual data and vestibular cues.
The domain of sensory perception offers a fertile ground for extensive research, with philosophers, neuroscientists, and psychologists collaborating at the Centre for the Study of the Senses at the University of London’s School of Advanced Study.
In 2013, this esteemed center inaugurated its “Rethinking the Senses” initiative, spearheaded by my late colleague, Professor Sir Colin Blakemore. Through this project, it was elucidated that modulating the auditory feedback from one’s own footsteps can alter the subjective perception of body weight, making it feel lighter or heavier.
We also discovered that audioguides within the Tate Britain art museum, which adopt a persona whereby the model in a portrait addresses the listener directly, significantly enhance visitors’ recall of visual details within the artwork. Furthermore, it was determined that the ambient noise of aircraft operations interferes with our capacity to perceive taste, thus explaining why tomato juice is often recommended for consumption on flights.
While our perception of saltiness, sweetness, and sourness is diminished in the presence of white noise, the perception of umami remains largely unaffected. Given that tomatoes and tomato juice are particularly rich in umami compounds, the ambient noise of an aircraft cabin can actually amplify their savory flavor profile.
At our recent interactive exhibition, Senses Unwrapped, held at Coal Drops Yard in London’s King’s Cross, attendees have the opportunity to explore firsthand the intricate mechanisms of their senses and understand why their operation may diverge from common assumptions.
For instance, the size-weight illusion is demonstrably illustrated through a display of curling stones of varying sizes. Participants are invited to lift each stone and ascertain which feels heaviest. The smallest stone typically elicits the perception of greatest weight, but upon subsequent placement on a balancing scale, it is revealed that all stones possess identical mass. This discrepancy highlights the cognitive influences on sensory perception.
However, a multitude of phenomena constantly surround us that underscore the profound complexity of our sensory apparatus, provided we take a moment for mindful observation. Therefore, on your next excursion into the outdoors or during the enjoyment of a meal, consider pausing to acknowledge the remarkable synergy of your senses working in concert to facilitate your rich experiential perception.
