I came across the what are called the primacy and recency effects in an article on fake reviews.
Consumer psychologist Cathrine Jansson says some sellers might be aware of what is known as the primacy and recency effects. These theories state that people tend to remember the first and last items in a series better than those in the middle.
A little web searching turns up the article Serial-position effect on Wikipedia. “Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst.”
Clearly from the serial-position effect your first and last slides are by far the most important in your entire pitch deck.
What if you only had two slides to convey your entire message to investors? What would be the message on each slide? The graphic? Should these two slides be the first and last slides in your deck? What I’ve noticed is that most entrepreneurs do not pay enough attention to the very first slide in their deck, which typically just lists the name of the company and often the contact information for the founder (which belongs on the last slide, not the first!)
Clearly you need to spend a lot of time on that first slide. That should include coming up with a tagline that summarizes your product in a short and punchy line of text. Secondly you need an impactful graphic that supports your tagline. Try several variations on this slide until your mentors or advisors feel you have nailed it.
Your last slide needs to neatly summarize your pitch supported by a graphic. You may want to repeat your tagline as well.
When presenting give both your first and last slides more time on screen. Speak to those slides! Work on exactly how to open your presentation, perhaps with a venture origin story and how to close it, with why your product will be hugely successful. Keep in mind when doing a pitch at a contest or demo day when you may be one of many presenters that your last slide may stay up on screen until the next presenter gets to the stage. Take advantage of those few seconds with a killer closing slide.
One final point. As I tell my mentees, most people can only remember three things from a presentation. Due to the serial-position effect; the primacy effect will bias them to remember the message from the first slide, the recency effect will bias them to remember the message from the last slide. What other message will all those intervening slides convey that will be memorable?