Chapter 4. Wetware: The Human Side of Interfaces

Table of Contents

Novelty, Consciousness, and the Single Locus of Attention
Real Time Costs
Hick's Law and Fitts's Law
Habituation, Expertise, and Undo Operations
Interfaces and Flow
Buffering and Human Memory
Designing around Characters and Stories
Designing With Personas

Remarkably. all of the well-known computer interface...are designed as though their designers expect us to have cognitive capabilities that experiment shows we do not possess.

-- The Humane Interface (2000) Jef Raskin

In the Premises chapter chapter we set out some normative design rules for user interfaces. In this chapter we'll ground the most important of these rules in what is known about human cognitive psychology.[25]

Human beings are not designed for dealing with computers, so computers have to be designed for dealing with human beings. Effective user interfaces have to be designed around the cognitive capabilities that human beings evolved to cope with what evolutionary biologists refer to as the “environment of ancestral adaptation”, the East African savannah on which our ancestors hunted, mated, fought, raised young, and died for millions of years before newfangled inventions like fire, the wheel, writing, and (eventually) computers bubbled up out of the hominid forebrain.

Looking back at the evolutionary story can help us organize our understanding of what we have learned about the capacity of human beings to think, remember, and pay attention. These capacities have many curious quirks, limits and nonlinearities that are profoundly relevant to UI design. Those quirks are much easier to understand if we realize that the kind of logic-intensive thought that computers call on is a lately-developed add-on to an elaborate framework of pre-logical instincts and wired-in responses, one more adapted to coping with saberteeth than city life.

At the end of the chapter we'll discuss ways in which human social instincts can be co-opted to make the design of effective UIs easier.

[25] Much of the conceptual skeleton of this chapter is adapted, along with the chapter epigraph, from Jef Raskin's The Humane Interface [Raskin]