Every day we encounter hundreds of typefaces or fonts (I’m using these two terms interchangably — apologies to typology anoraks), but most of us would be hard pushed to name any of them beyond perhaps the default computer ones like Arial. But they are subtly influencing us all the time, nudging our sensibilities behind the backs of the very words they represent.

“Typography is very manipulative,” Neville Brody, a leading graphic designer, admits. “The choice of a font will tell you how you’ll react emotionally to the information before you’ve even read it. It’s an invisible level of communication. It’s to do with context, association and memory.”

There is a gender divide in typographical taste, according to Dr Aric Sigman, a consultant psychologist, with men preferring more rectilinear fonts and women favouring rounded ones. This could be purely cultural conditioning. Dr Sigman has studied the emotional impact of fonts and is convinced that they constitute a “second dialogue”. After analysing stern letters from bank managers, he concluded that they are “increasingly using fluffy, friendly fonts in a vain attempt to humanise their message”.

Font experts in the type-obsessed world of advertising advise against such obvious clashes between meaning and typography. “I hate it when banks talk to youths in yoofy typefaces,” says Julian Vizard, of the St Lukes agency. “It’s like William Hague turning up at the Notting Hill Carnival in a baseball cap.”

The problem is that there are too many fonts to choose from and it’s all too easy for computer users to go typographically berserk. It’s estimated that there are now 50,000 fonts available and Brody says this explosion is motivated by the commercial need to manipulate consumers: “If there was no manipulation in typography, there’d only be one typeface.”

There was only one typeface when Gutenberg developed the first printing press in the 15th century, simulating the ornate ecclesiastical hand of the scriptorium. The subliminal message of the original Gothic or Black Letter fonts was clear: the words were God and the words were with God.

In the 16th century a new and more elegant style was needed to enshrine classical thinking, resulting in so-called Roman typefaces. In the 17th and 18th centuries, fonts became more graceful, no longer doing obeisance to monastic script, and dominated by high-profile designers such as John Baskerville. He was a celebrity in his own right (“Have you read Baskerville’s Virgil?”) and was deeply eccentric. A staunch atheist and rationalist, he insisted on being buried upright in his own garden.

Fonts are often named after their designers (Caslon, Bodoni, Zapf); occasionally after the places that inspired them (Chicago, New York, Monaco, Geneva, Harlow . . . yes Harlow) and sometimes after authors (Byron, Shelley and, more recently, Richler). Many fonts have names purely intended to evoke their image: Neopolotik, Stormtrooper, Incywincyspider.

Their titles may be confusing, but, thankfully, all fonts can be simply divided into two categories: Serif and Sans Serif. Baskerville’s fonts had obvious “serifs” which projected from each letter and pointed the reader forward, the word serif being derived from schreef which is Dutch for “dash”. We had to wait until the 18th century for Modern fonts, with straight, pencil-thin serifs, designed by Didot and Bodoni.

Then, in 1816, the now-familiar Sans Serif style first appeared, “sans” meaning “without” in French. Sans Serif fonts have no serifs at all, resulting in a clean, modernist line. Sans Serif typography dominated the 20th century, with a blip in 1930s Germany, when the Nazis revived the medieval Fraktur style.

In 2005 we appear to be suffering from font overload. In the past year, I’ve changed my e-mail font from Arial 12 Black (a “rubbish font” according to Brody) to Tahoma 10 Blue, as someone told me that small fonts are more authoritative. But a CV consultant then informed me that I’m an “obvious Trebuchet”.

Perhaps I should opt for Times New Roman, which has been the most widely used font on earth since it was designed by Stanley Morison in 1932. It was specifically devised for The Times newspaper to combine cool classical elegance with legibility and a hint of the modern.

Morison was a mostly self-taught traditionalist and friend of sculptor-typographer Eric Gill. After analysing classics such as Bodoni and Gill’s Perpetua, inspired by the writing on Trajan’s column, he decided that The Times required a font demonstrating “strength of line, fineness of contour and economy of space”.

A special Times font committee was set up, including the Surgeon Oculist to His Majesty’s Household. They read articles in several typefaces and reported a “freedom from fatigue after a long session” with Times New Roman.

In a publicity pamphlet, the newspaper put the emphasis on modernity and easy legibility, arguing that it would “increase the comfort of reading” in 20th-century environments such as “cars and aeroplanes”. The Times continues to use a descendant of Morison’s font, called Times Classic. The original Times font is still hugely popular in publishing and has now replaced Courier on US diplomatic documents.

Graphic designers either love it or hate it. To Brody, Times New Roman is the chintz of print. “It’s as ugly as hell. It’s like an ugly relative who knows all the rules and comes round and tells you where to put everything.”

Intriguingly, though, it’s only adults who get themselves worked up about all this. In a recent survey of 250 children, 99 per cent of them didn’t notice fonts at all. But growing up, you quickly develop font memories and prejudices. It’s thought that CVs with inappropriate or preposterous fonts are rejected within 30 seconds. As February 14 approaches, do not write your Valentines in fonts reminiscent of government documents, bills or letters from the Inland Revenue, and, unless you want to look like a sad fop, avoid Comic Sans at all costs.

Off I go again. Font geeks like myself are united by only one thing: violent phobias against particular typefaces. Most of us have got it in for cuddly Comic Sans. It is, in my view, the typographical equivalent of bindweed and ought to be eradicated from polite society and confined to comic speech bubbles.

Font fanatics revel in such draconian diktats and delight in factions and fracas. We luxuriate in the typographical Babel that bombards us. So, to ruffle the pro-Comic Sans lobby, here’s one of my favourite jokes: A Comic Sans font walks into a pub. And the barman says: “Sorry. We don’t serve your type in here.”

Ian Peacock presents From Arial to Wide Latin, BBC Radio 4, Friday, 11am