Bilateral stimulation refers to stimuli (visual, auditory or tactile) which occur in a rhythmic pattern, alternating between the left and right side.
So, visual bilateral stimulation could involve watching a hand moving from left to right and back again. Auditory bilateral stimulation might involve listening to tones that are heard alternately in the left and right ears.
Tactile bilateral stimulation takes place in the Cats Paw induction. You can also see it at work in the method known as the Butterfly Hug.
Here is how the Butterfly Hug is described in The Anxiety Guide:
• Sit with your back straight. Do abdominal breathing. Imagine you have a little balloon in your stomach that you inflate each time you inhale and deflate as you exhale – slowly, deeply, smoothly.
• Observe what is happening in your mind, emotions and body, just as impartially as you would observe clouds in the sky.
• Cross your hands over your chest so that the middle finger of each hand is placed below your collarbone. The rest of your fingers will touch your upper chest. Your hands and fingers are as vertical as possible (pointing more toward your neck than your arms. You can interlock your thumbs, if you choose.
• Alternate the movement of your hands, right, left, simulating the flapping wings of a butterfly.
• Continue to breathe slowly and deeply, observing whatever is going through your mind and body (thoughts, images, sounds, odours, emotions and physical sensations) without changing, avoiding or judging anything. Observe it like clouds passing by.
Finally, this Video demonstrates Melissa Tiers using bilateral stimulation to assist someone with their anxiety: