I have been reflecting on the nature of technical presentations. The motivations are manifold, the potential audiences are diverse, the expected outcomes varied, and there are so many ways to sink into the quicksand of somnambulant soliloquy.
Addressing the Sleepy
Let's begin with one of the most fearsome challenges – the after dinner speech. There are more difficult audiences, such as a group of restive five year olds coming down from a sugar-induced high, but not many. As dessert and coffee are served, you may well find yourself wondering what moment of foolish weakness allowed you to accept such a speaking invitation. All is not lost if one remembers key rules.
An after dinner audience is neither the time nor the place to attempt feats of technical legerdemain or cite obscure technical references. Rather, anecdotes, levity and (especially) brevity are to be prized above all else. Remember, though, that wit and humor lie in the eye of the beholder. With an after dinner audience, a rambling discourse on the funarg problem, call by name and call by value cannot be ameliorated by a retelling of Nicklaus Wirth's self-deprecating anecdote that Europeans call him by name and Americans by value!
Unlike humor, however, you, as the speaker, are in full control of brevity. If you find yourself struggling to be inspiring or entertaining, be succinct. The clearest sign and most humbling omen that you have failed, beyond the obvious signs of boredom, is when the phrase "in conclusion" silences the scrape of dessert cutlery and inspires expectant and excited looks. Sadly, I have experienced that emotion, both as audience member and as speaker.
Addressing the Curious
At the other extreme lies the technical presentation, the one most familiar to researchers as an oral exegesis of a technical paper. It has its own pitfalls, for both experienced and novice presenters.
For the newcomer, I heartily recommend the late Peter Medawar's delightful book, Advice to a Young Scientist. Although some of his presentation advice is technologically dated, the humor and academic perspective are timeless. I simply note that a modern updating of Medawar's advice would be to use a laser pointer sparingly, particularly if one is nervous, because the existence of trembling hands is wonderfully magnified.
Even in steady hands, an invited presentation should not be a complete regurgitation of a paper's content. Rather, it should eschew details in favor of describing the problem, solution approach, outcomes and implications. Do not read your slides; talk to your audience. Your objective is to make the audience want to read your paper.
Remember that few things strike more fear into the heart of even a technical audience than such phrases as "Combining lemmas 5, 12, and 19, it is obvious that …" If one has to explain why something is obvious, it probably is not. Like house guests who leave while their company is still being enjoyed, one wants to leave the audience excited and curious to know more – not less.
Addressing the Future
Finally, there is the plenary conference presentation or the vision and policy overview. It should inspire and motivate, drawing on research experience and open problems. It is usually neither as detailed as a technical presentation nor as lighthearted as an after dinner speech.
When discussing high-performance computing policy and research challenges, I have often found myself among a cadre of friends who were offering their perspectives on the same issues. In that spirit, my friends, Jack Dongarra (Tennessee/ORNL) and Rick Stevens (Chicago/ANL), have reflected on how frequently memes transit presentation boundaries.
One of us will hear the other describe an interesting idea or effective summary of an idea, morph the idea or slide, incorporate it into our talk, and present it with the others in the audience at another venue. It often passes among us several times, massaged and adapted each time, until none of know its origin, but all are invested in it. More generally, that is how new research ideas evolve and grow.
Public speaking can be great fun. When done well, it is a form of performance art. Enjoy it, and help your listeners enjoy it also!