Introduction

Back in the Mid Bronze Age, an unexpected aha moment prompted Phoenician turquoise miners to use Egyptian hieroglyphs to write words in their own language. Their "experiment" gave origin to the first alphabet, which evolved into many modern alphabets, including the Roman letters used to write the present article. The new acquired possibility of representing the somewhat abstract but numerically limited sounds of a language, instead of an infinite number of concepts or words, was a game changer in the history of writing. However, as the systems morphed from icons into symbols, they lost their mnemonic strength. 
Language representation is not an easy endeavor. The flow of speech is perceived acoustically as a multitude of distinct audible vibration waves that propagate in the air. Different civilizations have devised distinct systems to represent language by means of visual signs. In order to address the semiotic nature of those systems we need to shortly refer to Peircean Semiotics, the theory of signs. According to him, there are three types of signs: symbols, icons and indices. 
Symbols are signs that are culturally constructed, need to be agreed upon, and then memorized by its users.  The Roman letter m is a symbol;  its relation to the sound it represents is arbitrary. Icons, conversely, are signs that resemble the object they represent. The ancient Chinese character for rain was iconic, easy to learn, because it looked like rain. Its logic was not based on representing the flow of speech per se, but concepts expressed by it. 
Indices, or indexes, however, follow a different logic. They are not arbitrary but do not resemble the referent either.  They are signified by posing a direct link between them and the object they represent. Uniskript signs are indexical because they refer to speech sounds, which are waves, by pointing to the articulatory features that produce them.
The three different types of signs are illustrated in the chart below, with an arrow indicating a continuum of abstraction from left to right.
 
          
In terms of learnability, symbols are more difficult to learn because they are arbitrary - they have to be rote memorized. Icons, on the other end of the continuum, are more intuitive because they visually resemble the referent. The problem in using icons to represent language is that thousands of icons are necessary to cover all possible words in a given language. Besides that, abstract concepts and grammar are not always easy to represent iconically. An indexical system, however, like uniskript, combines the easiness of a pictorial system with the economy of an alphabetic system. This versatility explains why people learn uniskript so much faster than Roman letters, on one end, or Chinese characters, on the other.
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The chart below illustrates what kind of shapes are used for each one of the phonological features considered relevant for a consonant in a given language. The technique employed to generate alphabets, called 4-Questions Technique, prompts the developer with a set of questions and a number of alternative answers for each one of the features.
After answering each one of these four questions, the analyst will have arrived to what we call the proto-uniskript alphabet, and will undergo a process of elimination of redundancy. 
Additionally to the above referred indexical nature, uniskript signs are also sensory congruent. Each shape incorporates some of the cross-modal correspondences previously established in the literature of sound symbolism. Saussure's claims that there is no link between a thing and its name constitute the basis for one of the most fundamental assumptions of the modern linguistics: the arbitrariness of the linguistic sign (1959).  Nevertheless, the debate about sound-shape-meaning symbolism is at least as old as Plato's 400 BC work called Cratylus. In this famous dialogue with Hermogenes, Cratylus hypothesizes that the movements of the mouth and tongue during the production of a sound somehow resemble some correlate semantic concepts. According to him, [r] would be naturally related to 'motion, rapidity' while [o] would naturally point to 'roundness'. Later, Sapir's research (1929) demonstrated that English speakers systematically associate the back vowel /a/ with 'largeness', but the front vowel /i/ with smallness. According to Monaghan et. all (2014-1):
"It is a long established convention that the relationship between sounds and meanings of words is essentially arbitrary—typically the sound of a word gives no hint of its meaning. However, there are numerous reported instances of systematic sound–meaning mappings in language, and this systematicity has been claimed to be important for early language development."
The phenomenon of sound-shape symbolism was explored also by Köger. His seminal experiment (1929) showed that most Spanish native speakers matched the nonword maluma with rounded shapes, and takete with angular shapes.  The experiment, later called "kiki-bouba effect", was replicated across a wide range of unrelated languages and showed that people tend to match words and such figures far more often than chance would predict.