I have tried making this(showQuotes) into a function and calling the function in between the curly brackets but they didn't work either?

	// Show quotes from DB
	var showQuotes = $('#single').load('quote-get-single.php');
	setInterval(function(){ showQuotes },3000);
When I insert the whole of the jQuery code in the curly's it works. How can I make this work with a var or a function ? or what is the correct way to do this.