Learning the pentatonic positions is an imperative endeavor for any guitar player. All of the great guitar players over the past half-century have used these scales; some players, like Eric Johnson for example, are almost exclusively pentatonic users. A simple way to fatten up your pentatonic vocabulary with little effort is learning how to connect the positions effectively; in this case, we are dealing with groupings of four notes and connecting two adjacent positions.
One advantage to playing the guitar is the ability to choose where you want to play a given note. In the tablature below, we are opting to stretch into the adjacent pentatonic position when playing groups of four. For those who see things more visually, as I do, we are lessening the vertical aspect and opting for a longer horizontal approach; we are also condensing two groupings of four to two strings instead of three. Less string jumping is always desirable, and if we were to maintain one position playing groups of four, we would eventually run into a group of four which travels three strings and has the bottom and top string only carrying the burden of one note respectively. This is inefficient and can really bog down the speed in which you can express a pentatonic phrase.
There is one minor catch to employing this technique, and it's the abandon of traditional fingering. In the jazz realm, most of the players bar fourths and roll their fingers to avoid making a double stop sound. When playing pentatonics in groups you inevitably encounter fourths. With this technique every note gets an independent finger, and although this method can be awkward at first I assure you it makes barring fourths look compromising.
Let me assess the technique and fingering behind the first exercise. It is replicated in the later examples as well.
Example one deals with the minor pentatonic scale and it's adjacent position. Both scales are given, and it would be wise to start seeing pentatonic scales side by side, two at a time; even more if you can handle it. Looking closely at the first group of four exercise, we see that the fingering is immediately different. We are playing the first minor third with a 1&3 fingering as opposed to a 1&4; we are preparing ourselves for the stretch to come. The first group of four in A minor is A, C, D and E, which is played on the E and A strings. The second group of four (C, D, E and G) will be changed. The E string has only one note in the second grouping (the C on fret #8), and the G string which would normally be played on the D string is moved horizontally onto the A string and played on fret #10. This is what now constitutes two groups of four, or 8 notes. See how we are covering those 8 notes on only two strings now?
The difficulty lies in the way we are going to finger and navigate the next sections moving upwards. We are using a 1, 2 & 4 fingering for the D, E and G notes on the A string. The next group of four starts on D on the A string, we will play D and E (a major second) with the 1 & 3 fingers and then G and A with the same exact fingers on the D string. This fingering reveals itself when we fret the A note (an octave from our beginning) with the third finger and then drop our middle finger down to play the E note on the A string a fourth below. This isn't a constant, we didn't employ this method for the first two groups because our minor third fit a different fingering but when playing fourths it is favorable to use the third finger for the higher string and drop down a fourth using your second (middle) finger. This will take some getting used to and isn't the easiest thing to explain without demonstration. Take refuge in the fingerings given and you will see the benefit of the seemingly demented fingerings. Shawn Lane used this method because it increased his dexterity and speed, and we all know what a monster he was. There is also the video I've uploaded which demonstrates the examples being played at a moderate tempo. It can be found under: Keith Whalen - Groups of four and the middle finger.