For these reasons, recent alternative approaches emphasize either pure subjective reports, such as ratings of stimulus visibility (Sergent and Dehaene, 2004), or second-order commentaries such as postdecision wagering (e.g., would you bet that your response was correct?; Persaud et al., 2007). The wagering method and related confidence judgements provide a high motivation to respond truthfully and in an unbiased manner (Schurger Bortezomib chemical structure and Sher, 2008). Furthemore, they can be adapted to nonhuman subjects (Kiani and Shadlen, 2009 and Terrace and Son, 2009). However, they can sometimes exceed chance level

even when subjects deny seeing the stimulus (Kanai et al., 2010). Conversely, subjective report is arguably the primary data of interest selleck compound in consciousness research. Furthermore, reports of stimulus visibility can be finely quantified, leading to the discovery that conscious perception can be “all-or-none” in some paradigms (Del Cul et al., 2007, Del Cul et al., 2006 and Sergent and Dehaene, 2004). Subjective reports also present the advantage of assessing conscious access immediately and on every trial, thus permitting postexperiment sorting of conscious versus nonconscious trials

with identical stimuli (e.g., Del Cul et al., 2007, Lamy et al., 2009, Pins and Ffytche, 2003, Sergent et al., 2005 and Wyart and Tallon-Baudry, 2008). Although the debate about optimal measures of conscious perception continues, it is important to acknowledge that objective assessments, wagering indices and subjective reports are generally in excellent agreement (Del Cul et al., 2006, Del Cul et al., 2009 and Persaud et al., 2007). For instance, in visual masking, the conscious perception thresholds derived from objective and subjective data are essentially identical across subjects (r2 = 0.96, slope ≈ 1) (Del Cul et al., 2006). Those data suggest that

conscious access causes a major change in the global availability of information, Ketanserin whether queried by objective or by subjective means, whose mechanism is the focus of the present review. Conscious access must be distinguished from the related concept of attention. William James (1890) provided a well-known definition of attention as “the taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought.” The problem with this definition is that it conflates two processes that are now clearly separated in cognitive psychology and cognitive neuroscience (e.g., Huang, 2010 and Posner and Dehaene, 1994): selection and access.