David Luke

The induction of synaesthesia with chemical agents: a systematic review

Despite the general consensus that synaesthesia emerges at an early developmental stage and is only rarely acquired during adulthood, the transient induction of synaesthesia with chemical agents has been frequently reported in research on different psychoactive substances. Nevertheless, these effects remain poorly understood and have not been systematically incorporated. Here we review the known published studies in which chemical agents were observed to elicit synaesthesia. Across studies there is consistent evidence that serotonin agonists elicit transient experiences of synaesthesia. Despite convergent results across studies, studies investigating the induction of synaesthesia with chemical agents have numerous methodological limitations and little experimental research has been conducted. Cumulatively, these studies implicate the serotonergic system in synaesthesia and have implications for the neurochemical mechanisms underlying this phenomenon but methodological limitations in this research area preclude making firm conclusions regarding whether chemical agents can induce genuine synaesthesia.

A placebo-controlled investigation of synaesthesia-like experiences under LSD

The induction of synaesthesia in non-synaesthetes has the potential to illuminate the mechanisms that contribute to the development of this condition and the shaping of its phenomenology. Previous research suggests that lysergic acid diethylamide (LSD) reliably induces synaesthesia-like experiences in non-synaesthetes. However, these studies suffer from a number of methodological limitations including lack of a placebo control and the absence of rigorous measures used to test established criteria for genuine synaesthesia. Here we report a pilot study that aimed to circumvent these limitations. We conducted a within-groups placebo-controlled investigation of the impact of LSD on colour experiences in response to standardized graphemes and sounds and the consistency and specificity of grapheme- and sound-colour associations. Participants reported more spontaneous synaesthesia-like experiences under LSD, relative to placebo, but did not differ across conditions in colour experiences in response to inducers, consistency of stimulus-colour associations, or in inducer specificity. Further analyses suggest that individual differences in a number of these effects were associated with the propensity to experience states of absorption in ones daily life. Although preliminary, the present study suggests that LSD-induced synaesthesia-like experiences do not exhibit consistency or inducer-specificity and thus do not meet two widely established criteria for genuine synaesthesia.

Anthropology and Parapsychology: Still Hostile Sisters in Science?

Abstract After a long, slow journey from the leather armchairs of its forefathers to out-of-body travels over Amazonian jungles, the anthropology of psi has progressed through a number of historical, methodological, and ontological developments. The course of this transformation from the detached and disbelieving dismissal of the occult to the engaged and emic entertainment of psi as a scientific possibility is discussed. Following a century of obscurity within anthropology, the notion of magic as psi finally found unique refuge within the anthropology of consciousness. Nevertheless, despite decades of research anthropological parapsychology can still be considered a completely nascent field of study and is speculated to remain so until its interdisciplinary imperative is actually fulfilled and its subject matter is shared fully by the disciplines that border it.

Psychedelic synaesthesia: Evidence for a serotonergic role in synaesthesia

The neurobiology of synaesthesia is receiving growing attention in the search for insights into consciousness, such as the binding problem. One way of decoding the neurocognitive mechanisms underlying this phenomenon is to investigate the induction of synaesthesia via neurochemical agents, as commonly occurs with psychedelic substances. How synaesthesia is affected by drugs can also help inform us of the neural mechanisms underlying this condition. To address these questions we surveyed a sample of recreational drug users regarding the prevalence, type and frequency of synaesthesia under the influence of psychedelics and other psychoactive substances. The results indicate that synaesthesia is frequently experienced following the consumption of serotonergic agonists such as LSD and psilocybin and that these same drugs appear to augment synaesthesia in congenital synaesthetes. These results implicate the serotonergic system in the experience of synaesthesia.

Rock Art or Rorschach: Is there More to Entoptics than Meets the Eye?

Abstract The recourse to entopic phenomena as an explanation of certain geometric rock-art imagery has generated considerable debate among archaeologists and anthropologists of consciousness, and even among neuropsychologists, to a lesser degree. Surprisingly little has been discussed concerning the philosophical location of this debate in relation to the mind-body problem of consciousness, however, and a new perspective presented here on the experience of form constants challenges current thinking. Considering the neuropsychological-shamanistic theory of Paleolithic rock art in light of visionary experiences among both the blind and the sighted, and under different states of altered consciousness, an argument is presented that form constants are not actually entopic as they are currently defined, that is, made within the eye and the visual cortex. It is suggested that the entoptic rock-art model is swayed by philosophical biases that force theorists to see what they want to see, somewhat like a Rorschach ink blot test, when, rather, it actually appears that there may be more to entoptics than meets the eye.

Archaeologies of Consciousness: Essays in Experimental Prehistory

This short collection of expansive essays and book reviews is the first publication completely written by Gyrus, editor of the late-1990s underground magazine Towards 2012 and the ongoing periodical Dreamflesh: A Journal of Ecological Crisis & Archaeologies of Consciousness. Much like Time & Mind, the title of this anthology reflects its author’s interest in exploring the prehistory of mind and its changing states of consciousness. This is not an academic text however—although academics may find it fascinating reading—and the author makes no bones about his exploratory methods.