The World Wide Web distribution of James Gibson's "Purple Perils" is for scholarly use with the understanding that Gibson did not intend them for publication. References to these essays must cite them explicitly as unpublished manuscripts. Copies may be circulated if this statement is included on each copy.

I. Functions of Stimulation

A. The arousing of activity (episodic stimulation)
- to initiate single reactions ("phasic" responses, both reflex and "voluntary")
- to initiate trains of reaction (motivating of action)
- to arouse sense-perceptions (both simple and complex)
B. The maintaining of sequential activity (continuous stimulation)
- to sustain posture and equilibrium ("tonic" responses)
- to sustain continuous perception (orientation and awareness of the environment)
C. The control of sequential activity (feedback, or guidance of performance)
- of locomotion toward a goal (avoiding obstacles)
- of changing a feature of the environment (removing an obstacle)
- of constructing a new object (shelter, tool, etc.)
- of achieving a relation with another individual
D. The carrying of external information - to specify events (episodic stimulation)
- to specify permanent features of the environment
- to specify objects
- to specify other individuals, their actions, and expressions

II. Functions of Response

A. Stimulus exploration
- to produce optimal stimulation of receptors (focusing of retinal image, convergence, pupillary adjustment, sniffing odors, head-turning to sound, etc.)
- to select relevant stimulation (fixating of eyes, and other acts of attention)
- to obtain informative stimulation (head and eye-movements, exploratory manipulation, exploratory locomotion).
B. Performance
- to maintain postural equilibrium
- to move about the environment (goal attainment)
- to manipulate things (problem solving)
- to communicate by expression, voice, or otherwise (social problem solving)
C. Play
- to exercise a motor skill
- to exercise a social skill
- to exercise a "creative" skill.