39 | Malcolm MacIver on Sensing, Consciousness, and Imagination

Episode Summary

Executive Summary: Sean Carroll and Malcolm MacIver discuss how sensory reach shapes cognition, arguing that long-range vision after the water-to-land transition created evolutionary pressure for planning, imagination, and eventually elements of consciousness. The conversation extends to climate action, prediction markets, and how cultural tools might extend our limited native planning horizon.

Main Topics: MacIver’s interdisciplinary path (Priority: 4/5): MacIver describes moving from self-taught beginnings to philosophy, computer science, cognitive science, neuroscience, neuroethology, and finally engineering-adjacent robotics, explaining how each stage fed his research on behavior and cognition. Electric fish as a model for sensorimotor systems (Priority: 5/5): The discussion uses weakly electric fish to show how artificial and biological sensing can be experimentally controlled, modeled, and linked to locomotion, including robotic replicas and virtual-reality-like setups. Sensory range and locomotion geometry (Priority: 5/5): MacIver explains how sensory and motor spaces can be described geometrically, and how fish with short-range electrosense or vision have very different reachable and actionable volumes in space. Water-to-land transition and the evolution of planning (Priority: 5/5): The core hypothesis is that when vertebrates moved onto land, vision became long-range enough to make planning worthwhile, favoring imagination and more complex cognition. Consciousness as imagination and self-modeling (Priority: 4/5): MacIver links a scientifically tractable notion of consciousness to the first animals that had to examine their own mental options to guide behavior, while staying separate from the philosophical ‘hard problem.’ Long-horizon thinking, climate change, and decision tools (Priority: 5/5): The conversation turns to hyperbolic discounting, human weakness at long-term planning, and proposals such as prediction markets to make distant risks like climate change and solar flares more salient. Octopus intelligence and alternative evolutionary routes (Priority: 3/5): They briefly discuss octopuses as a possible independent route to advanced cognition, though MacIver stresses uncertainty and the need for more evidence.

Key Arguments: Weakly electric fish are ideal for neuroscience because their sensory input can be tightly controlled experimentally, unlike many other modalities. Motion and sensing are tightly coupled: an animal’s locomotor strategy is shaped by the spatial structure of its sensorium. The transition from water to land dramatically increased visual range because air attenuates light far less than water, making planning and delayed action more useful. Planning only pays off when sensory range is sufficiently long and the environment has a moderate amount of clutter/structure; too little or too much clutter reduces its value. A scientifically useful definition of consciousness may be the emergence of imagination and self-referential planning, not the subjective ‘hard problem.’ Human planning is biologically constrained and too short-horizon for issues like climate change, so cultural or institutional tools are needed to extend it. Prediction markets may create ‘skin in the game’ that improves attention, belief accuracy, and engagement with long-term risks. Climate change and solar flare preparedness illustrate failures of native evolutionary discounting, since the costs are immediate but the benefits are long delayed.

Data Points: Electric fish size: 15 to 30 centimeters - Typical lab-studied apteronotid weakly electric fish Prey sensing distance: about 3.5 centimeters - MacIver’s estimate for a 15-centimeter weakly electric fish detecting millimeter-sized prey Electric eel shock output: 600 volts at an amp - MacIver contrasts electric eels’ weaponized electric discharge with weakly electric fish Time before land colonization: about 50 million years - Invertebrate life bloomed on land before vertebrate transition Eye-size increase before land transition: about 10 million years before - Fossil evidence suggests eye enlargement preceded the water-to-land transition Study participants: a little over 150 people - Climate prediction market study involving denialists and believers Stake per participant: $20 - Participants were given money to trade in the climate prediction market Prediction market duration: 30 days - Bets were made over a month on climate-related outcomes Human planning discounting: hyperbolic - MacIver and Carroll discuss humans as hyperbolic discounters Potential tax mechanism: 1% - MacIver suggests a tiny carbon tax could fund broader participation in prediction markets

Pivotal Quotes: "the first animal that had to examine its mental furniture in order to derive a useful behavioral program" — Malcolm MacIver: MacIver’s definition of a scientifically tractable route to consciousness "planning becomes much, much more useful, but only in a restricted range of clutter" — Malcolm MacIver: Explaining why environmental structure matters for the evolutionary value of foresight "We are stuck with the brains that evolution gave us. Can we do better than that?" — Sean Carroll: Carroll frames the practical question of extending human cognition and planning

Implications: The episode suggests cognition is deeply shaped by sensorimotor ecology, and that society may need external tools—markets, institutions, and culture—to overcome short planning horizons and manage existential risks.