Julia Simner on tasty words and hearing colours

Episode Summary

Executive Summary: This episode explores neuropsychologist Julia Simner’s research on synesthesia and related sensory differences, showing how unusual cross-wiring of the senses can shape perception, memory, creativity, and everyday life. Simner explains how she diagnoses synesthesia, how childhood and brain development influence it, how it links to autism and misophonia, and why her team is building a “periodic table” of sensory traits to map human sensory diversity.

Main Topics: Diagnosing synesthesia (Priority: 5/5): Simner explains the lab-based and informal tests used to identify synesthesia, including consistency, vividness, and specific letter/number-color associations. Career path shaped by chance (Priority: 4/5): She describes a series of serendipitous swerves—from chemistry to French, then psychology and psycholinguistics—that ultimately led her into synesthesia research. How synesthesia develops (Priority: 5/5): The conversation covers evidence that synesthetic associations crystallize in childhood and are influenced by diet, language, and phonemes rather than just meaning. Brain mechanisms and theories (Priority: 4/5): Simner discusses MRI findings, altered connectivity, neonatal pruning, and the idea that multiple theories help explain synesthesia rather than competing outright. Links to autism, personality, and cognitive strengths (Priority: 4/5): The episode highlights sensory sensitivity as a bridge to autism and notes that synesthetes often show strengths in vocabulary, memory, spatial processing, and creativity. Misophonia, family experience, and practical impact (Priority: 5/5): Simner connects her work on sound sensitivity to her son’s type 1 diabetes experience and describes how research led to diagnostics and exam accommodations for children with misophonia. Mapping sensory diversity (Priority: 5/5): She and colleague Louisa Renault have built a framework resembling a periodic table to organize sensory differences and predict newly discovered traits such as cardiophilia.

Key Arguments: Synesthesia is real, measurable, and diagnosable through consistent patterns over time rather than mere imagination or memory. The phenomenon exists on a continuum, but there is a clear point where subjective sensory cross-talk becomes synesthesia. Synesthetic experiences often develop in childhood and are shaped by early language and diet, not randomly assigned associations. Brain imaging supports the idea that synesthetes have different connectivity and active sensory regions even when only one sense is stimulated. No single theory fully explains synesthesia; developmental, structural, and evolutionary perspectives can all contribute pieces of the puzzle. Synesthesia is associated with a broader sensory profile that can include autism-linked sensory sensitivity and cognitive advantages. Misophonia can have serious mental-health and educational consequences, so it deserves formal recognition and accommodations. A systematic map of sensory diversity can reveal gaps in knowledge and help predict previously unrecognized sensory traits.

Data Points: Estimated prevalence of synesthesia: at least 4.4% - Simner cites screening studies showing synesthesia is more common than earlier estimates suggested. Approximate population ratio: about 1 in 23 people - Used to convey how widespread synesthesia may be. Childhood diet linkage: significant association - James Wannerton’s word-tastes were statistically tied to foods from his childhood diet. Number of children with synesthesia in Simner’s family: half - She says half of her children have synesthesia and the other half have aphantasia. Online hits for cardiophilia: at least 35,000 hits - Evidence that there is a sizable community with a special attraction to the sensation of one’s own heartbeat. Timeframe of son’s diabetes management: six years - Simner describes the long-term burden of her son’s type 1 diabetes after diagnosis. Needle sticks/injections: 15,000 times in six years - Used to illustrate the intensity of her son’s treatment burden. Exam accommodation: first academic year - She says this was the first year students with misophonia could request a quiet exam room.

Pivotal Quotes: "It’s really hard to know what life you’re living." — Julia Simner: On the difficulty of understanding other people’s subjective sensory experience. "I would come away thinking you potentially do have some form of number colour synesthesia." — Julia Simner: Her informal assessment of host Jim Al-Khalili after the synesthesia quiz. "What we’ve created is a kind of periodic table of sensory differences." — Julia Simner: Describing the sensory diversity network and how it organizes sensory traits.

Implications: The episode reframes unusual sensory experiences as measurable human variation, not pathology. It suggests future diagnostics, accommodations, and a broader cultural shift toward understanding and celebrating sensory diversity.