Studies of Zen Buddhist Monks
In a study that attracted much attention among meditation and biofeedback researchers during the 1960s, Akira Kasamatsu and Tomio Hirai, physicians at the University of Tokyo, studied the EEG changes exhibited during meditation by Zen teachers and their disciples (forty-eight in all) from Soto and Rinzai centers in Japan. For experimental control, they studied the EEGs of twenty-two subjects with no experience at meditation. They made EEG recordings; recorded their subjects' pulse rates, respiration, and galvanic skin response; and tested their responses to sensory stimuli during meditation. The recordings on the Zen monks were made during a weeklong retreat, or sesshin, at a Zendo, except for a few tests at the experimenters' laboratory. The Zen teachers and their most experienced students exhibited a typical progression of brain-wave activity during meditation, which Kasamatsu and Hirai divided into four stages:
* Stage 1: Characterized by the appearance of alpha waves in spite of opened eyes.
* Stage 2: Characterized by an increase in amplitude of persistent alpha waves.
* Stage 3: Characterized by a decrease in alpha frequency.
* Stage 4: Characterized by the appearance of rhythmical theta trains (Kasamatsu and Hirai, 1966).
Not all four stages were evident in every Zen practitioner, nor in any of the controls, but a strong correlation existed between the number of stages a given student exhibited and that student's length of time in Zen training. This correlation was supported by a Zen teacher's evaluation of each student's proficiency. The teacher ranked the students in three levels, without seeing their EEG records, and his rankings correlated well with Kasamatsu and Hirai's assessment of their EEGs.
The Kasamatsu-Hirai study also revealed significant differences between four Zen masters and four control subjects in their response to repetitive click stimuli. Like the Zen masters, the controls exhibited a blocking of alpha when a click sound first occurred, but they gradually became habituated to such stimuli so that their brain-wave activity no longer responded when a click was made. The Zen masters, however, did not become habituated, but continued to exhibit blocking as long as the stimuli continued. This finding indicates that Zen practice promotes a serene, alert awareness that is consistently responsive to both external and internal stimuli (Kasamatsu et al., 1957; Hirai, 1960; and Kasamatsu and Hirai, 1963).