Overview

Charles Tart emerged as a central figure in late-twentieth-century consciousness research by refusing the false choice between scientific rigor and the serious study of anomalous human experiences. His career spanned five decades and integrated three overlapping domains: the experimental psychology of hypnosis and altered states, parapsychological research on ESP and out-of-body phenomena, and the theoretical foundations of transpersonal psychology. Unlike researchers who compartmentalized these interests, Tart developed unified frameworks that treated altered states, psi functioning, and spiritual experience as legitimate subjects for scientific investigation.

His foundational contribution was methodological: he created quantitative, reproducible tools for measuring subjective states that had previously been treated as intrinsically private and unmeasurable. This work established that altered states could be studied with the same rigor applied to any other psychological phenomenon. Simultaneously, he argued that genuine science, as opposed to scientism, the dogmatic assertion that only materialist explanations are valid, could and should investigate parapsychological claims and transpersonal experiences without prejudice.

Life and career

Tart began his career in the 1960s at a moment when hypnosis research was dominated by behaviorist frameworks that treated hypnotic phenomena as learned behaviors or role-playing. He quickly recognized that the field lacked adequate methods for measuring the depth or intensity of hypnotic states. Working with colleagues including Ernest Hilgard at Stanford, he developed self-report scales that allowed participants to quantify their subjective experience of hypnotic depth in standardized, comparable ways. His early papers on hypnotic dreams and the measurement of hypnotic depth established him as a methodologist willing to take subjective experience seriously without sacrificing scientific precision.¹⁰¹¹¹²

In the mid-1960s, Tart began investigating the relationship between hypnotic suggestibility and responsiveness to suggestions in waking states. Working with Hilgard, he demonstrated that hypnotic induction and waking imagination could produce comparable levels of responsiveness to suggestions, challenging the assumption that hypnosis was a unique state with special properties.⁴ This work was foundational to understanding the mechanisms underlying hypnotic phenomena and laid groundwork for later investigations into the nature of consciousness itself.

By the late 1960s, Tart had begun integrating parapsychological research into his program. He edited the landmark anthology Altered States of Consciousness: A Book of Readings in 1969, which became a canonical text in the emerging field of consciousness studies.¹³ This collection brought together leading researchers, including Stanley Krippner, Montague Ullman, and others, and established altered states as a legitimate domain for scientific inquiry. The book’s success reflected a broader cultural moment, but Tart’s curation and theoretical framing gave the field intellectual coherence.

During the 1970s and 1980s, Tart conducted systematic laboratory investigations of out-of-body experiences. He worked with individuals who reported spontaneous OBEs and attempted to study the phenomenon under controlled conditions. His research identified physiological correlates of OBEs in some participants and, in one notable case, found strong evidence that a participant had acquired paranormal knowledge of the laboratory environment during an OBE.³ These studies were methodologically rigorous, they included controls for sensory leakage, documentation of target information, and careful analysis of the relationship between subjective report and objective evidence, yet they remained open to the possibility that OBEs involved genuine paranormal perception.

Tart’s theoretical work during this period culminated in his development of a systems-theory approach to altered states. Rather than defining altered states by lists of phenomena (hallucinations, time distortion, memory changes), he proposed that consciousness is composed of multiple interrelated subsystems (sensory, emotional, cognitive, motor) and that altered states involve reorganization of these subsystems.⁶ This framework proved influential because it could accommodate diverse altered states (hypnosis, meditation, psychedelic intoxication, dreaming, OBEs) within a single theoretical structure. He also articulated the concept of state-specific sciences, proposing that knowledge acquired in altered states might be valid within those states but would require different validation methods than knowledge acquired in consensus consciousness.⁷

In the 1990s and 2000s, Tart became increasingly concerned with the cultural and institutional suppression of scientists’ reports of paranormal and spiritual experiences. He founded the Archives of Scientists’ Transcendent Experiences (TASTE), an online repository where scientists could anonymously document their own experiences with psi phenomena, altered states, and spiritual experiences. In his letter announcing TASTE, he argued that the materialistic and reductionistic climate of contemporary science (what he termed “scientism”) actively harmed both individual scientists and the collective scientific enterprise by denying a fundamental dimension of human experience.⁹ TASTE represented an attempt to create institutional space for the integration of scientific rigor and personal transpersonal experience.

Throughout his career, Tart maintained active research programs in multiple domains. He investigated the effects of immediate feedback on ESP performance, finding that feedback improved learning in forced-choice ESP tasks.¹⁴ He examined the relationship between psychedelic drug experiences and psi functioning, exploring whether altered neurochemical states enhanced or inhibited paranormal perception.¹⁵ He also engaged with near-death experience research, offering critical commentary on methodological issues in NDE studies and defending the scientific legitimacy of investigating paranormal perception in NDEs.¹⁶

Research

Hypnotic depth and altered states measurement. Tart’s early research established that hypnotic depth could be measured reliably using self-report scales. His scales asked participants to rate their subjective experience along multiple dimensions (absorption, dissociation, time distortion, and others) and he demonstrated that these ratings correlated with behavioral measures of hypnotic responsiveness and with physiological indicators such as basal skin resistance.¹²¹² This work was significant because it validated subjective report as a legitimate form of scientific data, rather than treating it as inherently unreliable or unscientific. His methods became widely adopted in hypnosis research and consciousness studies more broadly.

Hypnotic dreams and experimental control. Tart conducted detailed investigations of dreams occurring during hypnosis, examining how hypnotic suggestions influenced dream content and structure. He developed methods for inducing dreams in hypnotic states and comparing them to spontaneous dreams and dreams occurring in sleep.¹⁰¹¹ He also identified experimenter bias as a potential confound in hypnosis research, demonstrating that experimenters’ expectations could influence participants’ hypnotic performance.¹⁷ This work contributed to methodological standards in consciousness research by highlighting the importance of controlling for experimenter effects.

Hypnotic suggestibility versus responsiveness to suggestions. In collaboration with Ernest Hilgard, Tart demonstrated that responsiveness to suggestions in waking imagination conditions could equal or exceed responsiveness in hypnotic conditions.⁴⁵ This finding challenged the assumption that hypnosis was a unique state conferring special susceptibility to suggestions. Instead, it suggested that suggestibility was a trait that could be expressed in multiple states, and that hypnotic induction might not be necessary for producing suggestion-responsive behavior. The work refined understanding of the mechanisms underlying hypnotic phenomena and contributed to theoretical debates about the nature of hypnosis.

Out-of-body experiences and paranormal perception. Tart’s laboratory studies of OBEs represented some of the most rigorous investigations of the phenomenon conducted in the 1970s and 1980s. He worked with individuals who reported spontaneous OBEs and attempted to create conditions under which OBEs could be induced and studied. In one study, he placed a five-digit number on a high shelf in his laboratory and instructed a participant to attempt to view it during an OBE. The participant reported an OBE and, upon waking, accurately reported the number.³ While a single case does not constitute definitive proof of paranormal perception, the study was methodologically sound and demonstrated that OBEs could be investigated scientifically without assuming a priori that they were purely subjective hallucinations.

Tart also investigated the physiological correlates of OBEs, finding distinctive patterns of brain activity and autonomic nervous system function in some participants during reported OBEs.³ He explored the theoretical implications of OBEs, arguing that they challenged simplistic models of consciousness as identical to brain function, while remaining agnostic about whether OBEs involved actual separation of consciousness from the body or represented a complex form of mental simulation.

Systems theory of altered states. Tart’s most influential theoretical contribution was his systems-theory approach to altered states of consciousness. Rather than defining altered states by lists of phenomena, he proposed that consciousness consists of multiple interrelated subsystems, sensory processing, emotional regulation, cognitive function, motor control, memory, and others, and that altered states involve reorganization of these subsystems.⁶ This framework could accommodate diverse phenomena: in hypnosis, cognitive control might be enhanced while critical evaluation is reduced; in meditation, sensory input might be attenuated while emotional equanimity increases; in psychedelic states, sensory processing might be dramatically altered while emotional intensity increases. The systems approach provided a unified theoretical language for discussing altered states without reducing them to a single mechanism.

Tart also developed the concept of state-specific sciences, proposing that knowledge acquired in altered states might be valid within those states but would require different validation methods than knowledge acquired in consensus consciousness.⁷ This idea was radical because it suggested that consensus consciousness was not the only valid epistemic framework, and that other states might provide access to knowledge or experiences unavailable in ordinary waking consciousness. The concept influenced transpersonal psychology and consciousness studies, though it remained controversial in mainstream psychology.

ESP learning and feedback. Tart investigated whether ESP performance could be improved through training and feedback. He found that immediate feedback enhanced learning in forced-choice ESP tasks, suggesting that ESP functioning could be treated as a learnable skill rather than a fixed trait.¹⁴ He also examined the relationship between information acquisition rates and ESP performance, finding that precognition did not function as reliably as present-time ESP in laboratory conditions.⁸ This work contributed to understanding the conditions under which psi functioning could be reliably demonstrated and suggested that training protocols might enhance ESP performance in laboratory settings.

Psychedelic experiences and consciousness. Tart conducted research on the relationship between psychedelic drug experiences and consciousness, examining how altered neurochemical states influenced perception, cognition, and spiritual experience. He investigated marijuana intoxication and its relationship to psi functioning and spiritual experiences, and explored how previous psychedelic experiences influenced students of Tibetan Buddhism.¹⁵¹⁸ This work was controversial because it took seriously the possibility that psychedelic states could provide genuine insights into consciousness and reality, rather than dismissing them as mere neurochemical artifacts.

Near-death experiences and paranormal perception. Tart engaged with near-death experience research, offering critical commentary on methodological issues and defending the scientific legitimacy of investigating paranormal perception in NDEs. He critiqued skeptical analyses of famous NDE cases, arguing that critics often misrepresented the evidence or made unfounded assumptions about the physiological state of NDE experiencers.¹⁶ He also collaborated with other NDE researchers to examine the relationship between NDEs and expanded consciousness, arguing that NDEs demonstrated the existence of forms of consciousness and perception that transcended ordinary neurological function.¹⁹

Influence and reception

Tart’s influence on consciousness research and parapsychology has been substantial and multifaceted. His self-report scales for measuring hypnotic depth became standard tools in hypnosis research and consciousness studies, establishing that subjective experience could be quantified and studied scientifically. His systems-theory approach to altered states provided a theoretical framework that unified diverse phenomena and influenced the development of transpersonal psychology as a distinct field. His work on out-of-body experiences demonstrated that paranormal phenomena could be investigated in laboratory settings using rigorous methodology, contributing to the legitimacy of parapsychological research.

Beyond specific empirical contributions, Tart’s broader intellectual project, the integration of scientific rigor with openness to paranormal and spiritual phenomena, shaped the trajectory of consciousness research. He argued persistently that genuine science required openness to evidence, even when that evidence challenged materialist assumptions. His critique of scientism as a distortion of genuine science influenced philosophers and scientists working at the intersection of consciousness studies and parapsychology. His founding of TASTE represented an institutional attempt to create space for scientists to acknowledge and discuss their own paranormal and spiritual experiences without fear of professional consequences.

Tart’s work has been influential in transpersonal psychology, where his theoretical frameworks and empirical investigations of altered states, OBEs, and spiritual experiences provided foundational concepts and research paradigms. His emphasis on state-specific knowledge and the validity of experiences acquired in altered states contributed to transpersonal psychology’s theoretical distinctiveness. His integration of parapsychological research into consciousness studies helped establish that psi phenomena were relevant to understanding consciousness itself, rather than being marginal curiosities.

In mainstream academic psychology, Tart’s work has been more controversial. His willingness to investigate paranormal phenomena and spiritual experiences, and his critique of materialism as a limiting philosophical framework, placed him outside the dominant paradigm. However, even critics have acknowledged the methodological rigor of his investigations and the theoretical sophistication of his frameworks. His work on hypnotic depth measurement and the mechanisms of hypnotic suggestibility has been widely accepted and incorporated into standard practice in hypnosis research.

Tart’s legacy extends beyond specific empirical findings or theoretical concepts. He modeled a form of scientific practice that combined rigorous methodology with intellectual openness to phenomena that challenge conventional assumptions. He demonstrated that parapsychology and consciousness studies could be conducted with the same standards of evidence and reasoning applied in mainstream psychology, while remaining open to possibilities that materialism excludes. His career exemplified the possibility of maintaining scientific integrity while investigating questions that most of the scientific establishment considered illegitimate or unscientific.