Our human interface with reality

The Bottleneck is the limited rate that we can learn new information from outside, but some remarkably convincing evidence for our learning bottleneck comes from things we do in the world, i.e. when information flows outwards. This may seem counter-intuitive, but whenever we perform an action that must be monitored through our senses, then our learning bottleneck can intervene and dominate.

This is where we must discriminate between performing entirely as a learned skill, and actions that require supervision through our senses. Most of what we do involves both, but the learning bottleneck becomes evident when performing many physical activities.

Psychologist Paul Fitts at the Laboratory of Aviation Psychology, of Ohio State University, explored ways of measuring how subjects performed various manual skills. He had been fascinated by the observation that it takes the same time to handwrite individual letters, irrespective of their size. He devised various experiments to measure the maximum speed that subjects could perform a variety of physical actions, and used Shannon’s information theory as a way of characterising the degree of difficulty in bits. This enabled him to characterise the performance in bits per second, and to everyone’s surprise, a wide range of experiments revealed remarkably similar figures of less than 10 bits per second.

Bit Rate for Fitts’ Reciprocal Tapping task

Plots of bit rate versus task difficulty revealed a remarkably constant bit rate over a wide range of conditions.

“The Information Capacity of the Human Motor System in Controlling the Amplitude of Movement”, Paul M. Fitts, Ohio State University, 1954

The measured bit rate was essentially independent of the size of movements and the muscular strength required. This has puzzled many until now.

Subsequent research has found similar bit rates movements of other parts of the body such as the head or feet:

“Fitts’ law as a research and design tool in human-computer interaction”, I. Scott MacKenzie, Human-Computer Interaction, volume 7, 1992, pp., 91–139

Fitts’ Law is used extensively in wherever human machine interaction is required, such as in the size an positioning of elements on web pages or controls within vehicles. However, there has been no satisfactory explanation until now:

The Bottleneck explanation is that any skilled physical activity that must be supervised in real-time through the senses, can only continue as fast as the senses and brain can estimate whether the task is continuing appropriately. This involves learning, taking in information (e.g. 2D visual) and interpreting it in the context of a 3D internal model of the task out there.

So the bottleneck constrains the rate that we can interact with the world. That is why familiarity (practice) and attention (sensing the most valuable bits of information) are so crucial to skills.

Now compare with previously learned skills

Skills without visual monitoring such as the Knife Game or Five Finger Fillet