"Reality is merely an illusion, albeit a very persistent one.”
Perceptual Awareness, Suppression & Ambiguity
“What has to happen in the brain to generate a conscious experience?” The majority of my research is motivated by this general question. There are a million different ways to address this question, but most of my work focuses on ambiguous stimuli and other illusions that involve big perceptual changes or large parts of an image disappearing completely. As an example, if you look at the Necker cube on the right, the blue section should appear to alternate between the front and back face of the cube. Or the rotating sphere above that can appear to rotate either from right to left or left to right. An even more striking example is binocular rivalry, a phenomenon that occurs when different stimuli are presented to the left and right eye simultaneously. Despite the fact that the two images are always being presented, people generally report only seeing one of the images at a time because the other image is completely suppressed from awareness (click here for a binocular rivalry tutorial). Another illusion that generates complete perceptual suppression is Motion Induced Blindness (click here for MIB demonstration).
“What role does pharmacology play in determining our perceptual experience?”
A lot of research has shown that neurotransmitters (and drugs that target these neurotransmitter systems) have a huge impact on emotion and arousal, but less is known about the role of neurotransmitters in shaping our sensory experience. In an attempt to investigate this question I have studied some of the perceptual effects of hallucinogens and other drugs that disrupt the serotonergic system (click here for a tutorial about hallucinogens and perception).
(Click here for more information about current/previous research and collaborators)
Carter, O. & Pettigrew, J. (2003) A Common Oscillator for Perceptual Rivalries? Perception 32 (3): 295-305 [PDF]
Carter, O., Campbell, T., Liu, G. B. & Wallis, G. (2004) Contradictory influence of context on predominance during binocular rivalry. Clin Exp Optom 87 (3): 153-162 [PDF]
Carter, O., Pettigrew, J., Burr, D., Alais, D., Hasler, F. & Vollenweider, F. X. (2004) Psilocybin impairs high-level but not low-level motion perception. Neuroreport 15 (12): 1947-1951 [PDF]
Carter, O., Pettigrew, J., Hasler, F. & Wallis, G., Liu, G. B., Hell, D., & Vollenweider, F. X. (2005) Modulating the rate and rhythmicity of perceptual rivalry alternations with the mixed 5-HT2A and 5-HT1A agonist psilocybin. Neuropsychopharmacology 30: 1154-1162 [PDF]
Carter, O., Presti, D., Callistemon, C., Liu, G. B., Ungerer, Y. & Pettigrew, J. D. (2005) Meditation Alters Perceptual Rivalry in Tibetan Buddhist Monks. Current Biology 15(11): R412-R413 [PDF] (supplementary material [PDF])
Carter, O., Burr, D., Pettigrew, J. D., Wallis, G. M., Hasler, F. & Vollenweider, F. X. (2005) Using psilocybin to investigate the relationship between attention, working memory and the Serotonin1A and 2A receptors. J Cog Neuroscience 17(10): 1497‑150 [PDF]
Wittmann, M., Carter, O., Grimberg, U., Hasler, F., Cahn, R., Hell, D., Flohr, H. & Vollenweider, F. X. (2007) Effects of psilocybin on time perception and temporal control of behaviour in humans. J Psychopharmacology 21(1): 50-64 [PDF].
Carter, O. & Cavanagh, P. (2007) Onset rivalry: Brief presentation isolates an early independent phase of perceptual competition PLoS ONE 2(4): e343 [PDF].
Carter, O., Hasler, F., Pettigrew, J.D., Wallis, G., Liu, G. B. & Vollenweider, F. X. (2007) Psilocybin links binocular rivalry switch rate to attention and subjective arousal levels in humans. Psychopharmacology 195: 415-424 [PDF].
Einhäuser, W., Stout, J., Koch, C. & Carter, O. (2008) Pupil dilation reflects perceptual selection and predicts subsequent stability in perceptual rivalry. Proc Natl Acad Sci 105(5): 1704-1709 [PDF].
Snyder, J., Carter, O., Lee, S.K., Hannon, E. & Alain. C. (2008) Effects of Context on Auditory Stream Segregation. J Exp Psychol: Hum Percept Perform. 34(4):1007-16 [PDF]
Einhäuser, W., Stout, J., Koch, C. & Carter, O. (2008) Reply to Hupé et al.: The predictive correlation of pupil dilation and relative dominance duration in rivalry is not a statistical artifact. Proc Natl Acad Sci. 105:E44 [PDF]
Carter, O., Konkle, T., Wang, Q.,
Snyder, J., Carter, O., Hannon, E. & Alain. C. (In Press) Multiple levels of representation in auditory stream segregation: Evidence from context effects. J Exp Psychol: Hum Percept Perform.
Naber, M., Carter, O. & Verstraten. F. (Submitted) Suppression wave dynamics reveal visual field anisotropies and sensitivity to inducer strength.
Snyder, J., Holder, W. T., Weintraub, D. M., Carter, O., & Alain, C. (Submitted) Effects of prior experience are distinct from stimulus encoding during auditory perception.
Cochi, L., Bosisio, F., Carter, O., Wood, S., Berchtold, A., Conus, P., Orita, A., Debbané, M. & Schenk, F. (Submitted) Deficit dissociation between visuospatial working memory and visual pursuit processes in schizophrenia.
Einhäuser, W., Koch, C. & Carter, O. (Submitted) Pupil dilation betrays the timing of decisions.
Carter, O., Snyder, J., Rubin, N. & Nakayama, K. (In Preparation) Contrastive effects of prior context on plaid motion segregation.
Carter, O., Luedeman, R. Mitroff, S. & Nakayama, K. (In Preparation) Motion Induced Blindness: The more you attend the less you see.
Pettigrew, J. & Carter, O. (2002) Vision as motivation: interhemispheric oscillation alters perception. Adv Exp Med Biol 508: 461‑9
Pettigrew, J. & Carter, O. (2004)
Perceptual Rivalry as an Ultradian Oscillation. In: Binocular rivalry.
(Eds.) David Alais and Randolph Blake, MIT Press,
(Click here for links to talk and poster presentations)
Department of Psychology
School of Behavioural Sciences
Phone: +61 (0)3 83446372
Tutorial - Binocular Rivalry [PDF]
Tutorial - Hallucinogens and Perception [PDF]
Resources for students and teachers of visual perception (www.viperlib.com)
Last updated: Nov 2008