Helmholtz Lecture Tim Brady, February 27: Visual memory as a window into the nature of mental representations

Helmholtz lecture Tim Brady (Department of Psychology, University of California San Diego)

Title: Visual memory as a window into the nature of mental representations

Abstract: 

In the real world, objects are discrete physical entities – your coffee mug either is or is not in your hand. As a result, both in everyday life and in perception and memory research, there is a tendency to use a physical metaphor to understand our mental representations: people tend to think of an object they are trying to perceive or remember as either in mind or not in their mind, and to say that we hold items in memory, as we hold real objects in our hand. In the domains of visual working memory, visual long-term memory and perceptual awareness, this discrete thinking is often formalized using models that fit psychophysical data, and are based on the premise that people often completely lose an item from memory or completely fail to encode or perceive an object. In this talk, I’ll review our recent work re-examining this view and suggesting a simple alternative model motivated by neural population coding and representational geometry. This model accounts for large swaths of data on visual memory and perceptual awareness with only a concept of a continuously varying memory match signal, and without any concept of discrete all-or-none failures. A core aspect of this model – key to understanding this model’s simplicity – is that the underlying representation of even simple features tends to be very high-dimensional (e.g., as in population codes, or in the features extracted from deep nets), and that in high-dimensional spaces, the strength of representational match signals tends to fall off highly non-linearly. Thus, I’ll argue considering the complex, high-dimensional nature of the neural representation of stimuli can, counterintuitively, lead to very straightforward cognitive models of perception and memory. 

Location: Ruppert Paars (Leuvenlaan 21, Utrecht)

Helmholtz Lectures take place from 4 to 5pm, with drinks afterwards next to the lecture room.

Helmholtz agenda: https://helmholtzschool.nl/category/agenda/

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