The Forgetting Machine

1. Memory is a Construct, Not a Recording

Most of what we do, see, and remember is filtered, interpreted, and inferred.

Reconstruction, not reproduction. Our brains don't faithfully record every detail of our experiences like a video camera. Instead, memory is a reconstructive process where we piece together fragments of information, filling in the gaps with assumptions and inferences. This means our memories are subjective and prone to distortion.

Memory's malleability. The act of recalling a memory can change it. Each time we retrieve a memory, we essentially rewrite it, potentially incorporating new information or biases. This malleability makes eyewitness testimony unreliable and highlights the potential for false memories to form.

Implications for identity. Our sense of self is built upon this ever-changing collection of memories. While this can be unsettling, it also underscores the brain's remarkable ability to create a coherent narrative from limited and imperfect information, allowing us to navigate the world with a sense of continuity and purpose.

2. Vision is Selective, Not Comprehensive

The illusion arises from the fact that our eyes continually jerk from side to side, making unconscious movements called saccades.

Foveal focus. We only see the world in high detail within a small area at the center of our gaze, the fovea. Our eyes constantly dart around, making rapid, unconscious movements called saccades, to gather information from different parts of our visual field.

Brain fills in the gaps. The brain creates the illusion of a detailed, comprehensive view by stitching together these snapshots and filling in the gaps with assumptions and expectations. This is why we often don't notice details outside of our direct focus.

Artistic manipulation. Artists exploit this selective nature of vision by guiding our gaze and emphasizing certain elements while downplaying others. This allows them to create a specific emotional response or convey a particular message.

3. Perception Relies on Unconscious Inferences

The brain makes unconscious inferences in order to assign a meaning to what we see.

Helmholtz's theory. Hermann von Helmholtz argued that our brains make unconscious inferences based on past experiences to interpret sensory information. We don't see copies of reality, but rather signs or constructions fabricated in our brains.

Optical illusions. Optical illusions demonstrate how the brain uses these inferences to create meaning. The Kanizsa triangle, for example, shows how we perceive shapes even when they are not explicitly drawn, based on our prior knowledge and expectations.

Blindness recovery. Cases of individuals who regain sight after being blind from birth highlight the importance of experience in perception. They often struggle to recognize objects initially, demonstrating that sight is not simply a passive recording of visual information, but an active process of interpretation.

4. Forgetting is Essential for Abstraction

Paradoxically, it is necessary to forget in order to remember; if we were to remember everything, we would be as handicapped as if we remembered nothing.

Filtering irrelevant details. Forgetting allows us to filter out irrelevant details and focus on the essential information needed to form concepts. This abstraction process is crucial for generalization and understanding.

Borges's "Funes the Memorious." The character Ireneo Funes, who remembers every detail of his experiences, is incapable of abstract thought. He cannot grasp the concept of "dog" because he is overwhelmed by the unique characteristics of each individual dog he has encountered.

Concept formation. By forgetting the specific details of individual instances, we can identify common characteristics and form abstract concepts. This allows us to categorize and understand the world around us.

5. Memory Capacity is Limited, Processing is Key

The human brain, on the other hand, concentrates its resources on attributing meaning to the paltry amount of information that reaches it from the senses.

Landauer's estimate. Thomas Landauer estimated that we only store about 125 MB of information in a lifetime. This is far less than the storage capacity of a modern flash drive, highlighting the brain's focus on processing rather than simply storing data.

Meaning over fidelity. The brain prioritizes meaning construction over faithful reproduction. It selects a tiny amount of information and processes it redundantly to extract meaning, discarding a multitude of details.

Assumptions and inferences. We fill in the gaps in our memories with assumptions based on past experiences. This allows us to create a coherent narrative, but also makes our memories prone to distortion and false recollections.

6. Mnemonics Organize, Not Enhance, Memory

Simonides inferred that sorting memories was the key to preserving them, and he went on to invent mnemonics, the art of harnessing various techniques to enhance memory.

Method of loci. The method of loci, associating items with specific locations, is a mnemonic technique that helps organize memories. It doesn't increase our overall memory capacity, but rather provides a structure for retrieving information.

Historical significance. Mnemonics were crucial in antiquity when there were no writing tools. Orators relied on memory techniques to deliver speeches and arguments.

Modern relevance. While modern technology has reduced the need for rote memorization, mnemonics can still be useful for specific tasks, such as remembering names or lists. However, they don't necessarily improve general memory abilities.

7. Concepts are Encoded by Neural Networks

I had seen, for the first time, a neuron that responded to a concept.

"Jennifer Aniston neurons." Researchers have discovered neurons in the human brain that respond selectively to specific concepts, such as the actress Jennifer Aniston. These neurons fire in response to different images and representations of the same concept.

Hierarchical processing. The visual system processes information in a hierarchical manner, moving from simple features like lines and edges to complex representations like faces and objects. Concept neurons represent the end result of this processing.

Associations and memory. These concept neurons are interconnected, forming networks that encode associations between related concepts. This network structure is thought to be the basis of memory and our ability to recall related information.

8. The Mind is Embodied in Brain Activity

“You,” your joys and your sorrows, your memories and your ambitions, your sense of personal identity and free will, are in fact no more than the behavior of a vast assembly of nerve cells and their associated molecules.

Materialism vs. dualism. The book leans towards a materialistic view, suggesting that the mind is a product of brain activity, rather than a separate entity. This contrasts with Cartesian dualism, which posits a separation between mind and body.

Philosophical zombies. The thought experiment of philosophical zombies challenges the materialistic view. If a perfect physical copy of a person could be created, would it necessarily have consciousness?

Implications for AI. If the mind is simply brain activity, then it is conceivable that a sufficiently advanced computer could achieve consciousness. However, the question of how to test for consciousness in machines remains a challenge.

9. Animals Exhibit Varying Degrees of Consciousness

It is undeniable that higher primates have self-awareness, and it is likely that dogs, cats, and various other animals have it too—despite not passing the mirror test.

Mirror test. The mirror test, where animals are marked and then observed in front of a mirror, is used to assess self-awareness. Some animals, like chimpanzees and dolphins, pass the test, while others do not.

Animal memory. Many animals have impressive memory capabilities, such as scrub jays remembering thousands of food hiding places. This suggests that memory is not uniquely human.

Degrees of consciousness. Consciousness may exist on a spectrum, with different species exhibiting varying degrees of self-awareness and cognitive abilities. Humans, with our advanced language and abstract thought, represent one end of this spectrum.

Last updated: February 26, 2025