The Behavioral and brain sciences
December 1, 2007
Ned Block
1,123 citations
A puzzle arises in trying to separate the brain basis of phenomenal consciousness—the raw subjective experience—from the machinery needed to report that experience. The standard method of identifying neural correlates in clear cases (where people are certain and authoritative) is circular: it already assumes whether report-related machinery is part of the conscious state. The paper argues for an abstract solution and points to empirical evidence that phenomenal consciousness can overflow cognitive accessibility—that is, we can have conscious experiences we cannot report. It proposes that the neural basis of consciousness can be identified by excluding the neural basis of accessibility, an assumption justified by the explanations it enables.
Trends in Cognitive Sciences
January 13, 2005
Ned Block
715 citations
The search for a single neural correlate of consciousness (NCC) may be misguided. Evidence increasingly supports a framework with at least two distinct NCCs: a phenomenal NCC and an access NCC. These can be distinguished using experimental methods such as signal-detection theory. Recent cognitive neuroscience findings provide empirical support for two separate NCCs rather than one.
Trends in Cognitive Sciences
September 1, 2014
Ned Block
125 citations
A new technique suggests that people can consciously perceive more items at once than can be held in visual working memory. The method exploits unattended 'ensemble properties' that can be detected without reducing working memory capacity, offering a way to study phenomenal consciousness beyond memory limits.
Science
January 25, 2018
Olivia Carter, Jakob Hohwy, Jeroen J A Van Boxtel et al.
86 citations
A commentary argues that Dehaene et al.'s review on consciousness and machines asks and answers the wrong questions, implying that their conclusions about not being on the verge of creating conscious machines may be premature or misdirected.
Trends in Cognitive Sciences
April 1, 2026
Ned Block
Computational functionalism holds that running certain computations is enough for consciousness, no matter what physical system does the computing. This view overlooks the possibility that the subcomputational biological mechanisms that actually carry out those computations are essential for consciousness. Comparing computational roles with their biological realizers reveals a tension: prioritizing computational roles supports consciousness in AI, while prioritizing biological realizers supports consciousness in simpler animals. Current theories are 'meat-neutral', but if specific physical substrates are necessary, AI may never become conscious. Understanding whether consciousness depends on computational roles, biological realizers, or both is crucial for assessing consciousness in AI and less complex animals.
Trends in Cognitive Sciences
September 1, 2024
Ned Block
Decoding perceptual contents from the prefrontal cortex (PFC) has been used to test rival theories of consciousness, but the evidence is ambiguous. Failures to decode from the PFC challenge cognitive theories like global workspace theory and higher-order monitoring theories, while successes seem to confirm them. However, PFC decoding shows both too much and too little: cognitive theories do not require PFC rerepresentation of perceptual contents, as pointers suffice, and decoding may reflect postperceptual cognitive representation, such as thoughts about perceptual contents, rather than conscious percepts themselves. This suggests that decoding evidence does not straightforwardly adjudicate between theories of consciousness.
Encyclopedia of Cognitive Science
January 15, 2006
Ned Block
The most significant problem of consciousness is explaining how it can be understood in terms of its neural basis. This challenge, often called the hard problem of consciousness, asks how subjective experience arises from physical brain processes. The abstract identifies this as the central issue, distinguishing it from other, more tractable problems about consciousness that concern functions, behaviors, or correlates.
The Foundations of Cognitive Science
July 26, 2001
Ned Block
The concept of H2O and the concept of water are two concepts of the same thing, as are temperature and mean molecular kinetic energy. Conversely, in the seventeenth century, the ambiguous phrase 'degree of heat' denoted two concepts with different referents: measuring by paraffin melting ranked heat source A hotter than B, while measuring by ice-melting rate ranked B hotter than A. Today we recognize the former measured temperature, the latter heat. Similarly, Aristotle used 'velocity' to mean both average and instantaneous velocity, and failing to distinguish them caused problems.
Ned Block
Whether consciousness arises from biological processes rather than computational ones is central to understanding if machines could ever experience feelings and if simple animals might already possess conscious experience. The text questions the assumption that consciousness can be replicated in non-biological systems and suggests that biological substrates may be necessary for subjective experience.