The media item comes from the Discovery Channel, a noted environmental supporter and scientific supporter. However, the narrator does use sensationalist and non-objective language at times to increase interest in the item. The excerpt also contains Dr David Eagleman from the University of Texas, a leader in current research into the biological basis of synaesthesia. Eagleman has developed a standardised scoring system of synaesthesia and is co-authoring a book on synaesthesia. He is a reputable source, who has high competence in communication.
The target audience seems to be educated persons with little or no knowledge of the field. The video aims to be entertaining rather than educational, making statements such as "...some peoples' minds are so different, that their perceptions are literally turned upside-down.", even though their perceptions are not actually "upside-down", rather one perception elicits another.
The video goes on to artificially colour the frozen chicken that the subject is selecting with the colour that the taste purportedly elicits, even though it is not the visual perception of the foods but the taste that elicits the colours. The video is attempting to provide the audience with an insight into what the experience would be like for the synaesthete, but incorrectly attributes the colours in this way.
Dr. Eagleman, the expert in the video, provides relatively rudimentary explanations of the theoretical aspects of the condition. He explains the first theory, known as Cross Activation, by describing the different sensory regions of the brain as "neighbouring countries" with "porous borders". He then describes the theory concerning the pathways of inhibitory and excitatory neurons, known as Disinhibited Feedback, which Dr. Eagleman favours. According to disinhibited feedback theory, neural activation from sensory input reaches higher order cortical areas, which feed back to primary sensory areas. If this feedback is not sufficiently inhibited, it may cause excitation in other sensory modalities (Grossenbacer & Lovelace, 2001). While his explanations may be over simplified, it is appropriately pitched for the layman audience. It is also good that the professional acknowledges there are competing theories and that the phenomenon is not completely understood, and delivers a less sensational explanation than the general feel of the programme.
However, Dr Eagleman also suggests there may be a genetic component to synaesthesia, and likens it to the gene for eye colour. It is unlikely that such a complicated condition would be the result of a mutation in a single gene. Indeed, there are many different types and combinations of synaesthesia, and even people with the same type may not have the same experiences under the same conditions. This suggests a very complex genetic component, if in fact there is a genetic component at all. Shaun reports he first started experiencing the illusory colours when he was eight years old. This could suggest environmental causes, rather than genetics.
It is difficult to know if Shaun is being completely truthful about his experiences. He reports that both gustatory and auditory inducers elicit coloured visual concurrents. Grapheme-colour, lexical-gustatory, and audition-colour synaesthesia appear much more frequently in the research literature than gustatory-colour synaesthesia. While occasional case studies of gustatory-colour synaesthesia do exist (see Downey, 1911), it seems strange to use this type of synaesthesia as the primary example in the video. Furthermore, Shaun goes to (seemingly) extreme measures to obtain coloured illusions that he likes, frequently mixing chicken with icecream for dinner, even though he also reports to have normal gustatory function. This makes it seem possible that Shaun could be exaggerating his condition, perhaps to obtain media attention, although it is difficult to know for certain.
Overall, the excerpt uses language that is easy to understand and explores the extremes of the patient's condition. Even though it is slightly sensational, it still provides a reasonably accurate representation of synaesthesia and explains the current theories behind the condition without bias or misrepresentation. It is also interesting how they use special effects to represent synaesthesia from the synaethete's perspective, providing insight into the basis of this perception disorder.