If you believe in evolution, you must then believe that the world we perceive is not the world we actually inhabit. Not even close. The objects we see or hear or touch do not exist independently of the mind that constructs them. Our perception is nothing more than a useful fiction. This is the core of Hoffman, Singh, and Prakash’s Interface Theory of Perception and the claim that the present Special Issue examines in depth.

The idea is far from new. Indeed, philosophers have entertained it for centuries. But Hoffman and colleagues give the theory some empirical teeth and force us to take it seriously, along with its mind-blowing implications.

The empirical teeth come in the form of evolutionary game simulations and genetic algorithms to model natural selection. Scenarios were set up in which the probability of the evolution of different perceptual strategies could be assessed. The critical perceptual strategies in the virtual test tube consisted of (1) those that represented truth about the nature of the (simulated) world, or (2) those that favored fitness payoffs over truth. For example, imagine a world in which physically red and green objects have the same positive fitness payoff (they are equally nutritious) while blue and orange objects have the same negative fitness payoff (they are equally toxic). One can then ask, how often does a perceptual strategy evolve such that the organism perceives all four color categories veridically, i.e., they see the truth, versus another strategy in which the organism only sees two categories corresponding to fitness payoffs (red/green and blue/orange) rather than truth? The result of many such simulations under a range of scenarios is strikingly consistent: fitness wins every time and truth goes extinct. In fact, truth never gets on the evolutionary game board.

This should be no surprise. How could evolution favor veridical perception if the truth doesn’t help make babies? It can’t unless it does so accidentally (i.e., it’s a spandrel), which is highly unlikely given the complexity of our perceptual systems, or unless truth and fitness are monotonically related. Hoffman and colleagues offer arguments for why truth and fitness are generally unlikely to be monotonically related, for example, the need for homeostasis in biological systems. I can offer, in addition, a simple example. It is quite difficult to invoke “truth” to explain species-specific sexual attraction (humans are attracted to humans, baboons to baboons), whereas fitness considerations readily explain why beauty is in the eye of the (species) beholder.

Hoffman et al. call their model the Interface Theory of Perception (ITP) and illustrate it intuitively using a graphical user interface analogy. The desktop display of your computer shows a set of icons representing files, folders, operations (such as trash/delete), and apps. You don’t take that interface literally. You understand that your latest manuscript isn’t literally a little rectangle sitting in a clutter of other little rectangles in the upper left corner of your display. Rather that little rectangle is just a convenient icon that represents your manuscript. Similarly you understand that if you drag that little rectangle to the trashcan in frustration, the rectangle isn’t literally in the trashcan. Rather, the desktop is a convenient means to interface with the underlying reality of your computer. It’s useful because it hides the truth and presents instead a set of user-friendly shortcuts for writing papers, sending messages, and manipulating photos. Notice too how notions of causality play out in the interface. The cursor, the little rectangle, and the trashcan icons themselves have no causal power. It’s not the movement of the rectangle icon to the trashcan icon that causes the file to disappear; it’s the underlying electric currents and switches that actually have causal power. We understand this because sometimes something goes wrong with our GUI and a successful move of an icon from one place to another results in no actual effect (e.g., the drive doesn’t eject). Perception, Hoffmann et al. argue, is precisely the same: what we experience is nothing more than a set of species-specific icons, user-friendly shortcuts for staying alive and reproducing. Similarly, there is no causal power inherent to the objects we perceive. It appears that a tennis racquet can cause a ball to move, but that is nothing more than a juxtaposition of icons in our interface. The real causal powers are hidden from us, according to ITP.

The above is an excerpt of an introductory article that appeared in the Psychonomic Bulletin & Review today. You can read the remainder here (it will be open access for 6 months).

The other articles in this special package dedicated to interface theory are listed below and will remain open access for 3 months:

1. The main article introducing interface theory:



Donald Hoffman, Manish Singh, and Chetan Prakash: The interface theory of perception

2. Published commentaries on interface theory:

Barton Anderson: Where does fitness fit in theories of perception?

Jonathan Cohen: Perceptual representation, veridicality, and the interface theory of perception

Shimon Edelman: Varieties of perceptual truth and their possible evolutionary roots

Jacob Feldman: Bayesian inference and “truth”

Chris Fields: Reverse engineering the world

Jan Koenderink: Esse est Percipi & Verum est Factum

Rainer Mausfeld: Notions such as ‘truth’ or ‘correspondence to the objective world’ play no role in explanatory accounts of perception

Brian McLaughlin and E. J. Green: Are Icons Sense Data?

Zygmunt Pizlo: Philosophizing cannot substitute for experimentation

Matthew Schlesinger: The Interface Theory of Perception Leaves Me Hungry For More

3. Reply to the comments

Donald Hoffman, Manish Singh, and Chetan Prakash: Probing the interface theory of perception: Reply to commentaries

Starting tomorrow, for the remainder of this week, we will continue the discussion here on the Featured Content website of the Psychonomic Society. We will run three more original scholarly comments by Gary Lupyan, John Hummel, and Scott Jordan, followed by a reply by Don Hoffman.