Proto-organisms probably were randomly aggregated nets of chemical reactions. The hypothesis that contemporary organisms are also randomly constructed molecular automata is examined by modeling the gene as a binary (on-off) device and studying the behavior of large, randomly constructed nets of these binary “genes.” The results suggest that, if each “gene” is directly affected by two or three other “genes,” then such random nets: behave with great order and stability; undergo behavior cycles whose length predicts cell replication time as a function of the number of genes per cell; possess different modes of behavior whose number per net predicts roughly the number of cell types in an organism as a function of its number of genes; and under the stimulus of noise are capable of differentiating directly from any mode of behavior to at most a few other modes of behavior. Cellular differentiation is modeled as a Markov chain among the modes of behavior of a genetic net. The possibility of a general theory of metabolic behavior is suggested. Analytic approaches to the behavior of switching nets are discussed in Appendix 1, and some implications of the results for the origin of self replicating macromolecular systems is discussed in Appendix 6.

Cockroach legs bear tactile spines equipped with campaniform sensilla – mechanoreceptors associated with the cuticle – which function by a single bipolar neuron from whose dendrite tip extends a modified cilium packed with 350–1000 parallel cytoplasmic microtubules. These microtubules, which can be chemically disassembled with colchicine and vinblastine, are intimately associated with the site of mechanical stimulation. Treatment of living sensilla with colchicine and vinblastine abolishes their ability to respond to mechanical stimulation 1–2 hr after drug application. Loss of function is accompanied by large-scale disassembly of microtubules in the modified cilium. The experimental evidence strongly suggests that microtubules play an important role in the process of sensory transduction in campaniform sensilla.

When subjects learn a transformation skill in conditions that allow them to direct their attention freely to different subgoals, they adopt definite learning strategies which can be externalized by special techniques. Two of these techniques are described (expts. 1 and 2) and the free-learning strategies revealed with their assistance are discussed. Such strategies may also be used in ‘controlled learning’ conditions, i.e. when a subject is taught the skill. In this case, the (computerized) teaching system acts as a surrogate for, and may be viewed as a model of, the subject’s attention-directing mechanism. Experiment 3 is concerned with learning controlled by a conversational system which entails a model based on a class of learning strategies; expt. 4 with a simple adaptive system, based on a single learning strategy. There are marked differences between the form and efficiency of learning in the free conditions and each of the two controlled conditions. These differences are described and a theoretical interpretation is proposed.

This paper is an attempt to arrive at a species-specific characterization of human consciousness by considering its value as a biological adaptation. The analysis considers conscious phenomena in animals to motivate the distinction between self-consciousness and consciousness; the distinction is substantiated with neurological data. The relation between self-consciousness and language is considered in the light of the evolution of human language. Finally, a mechanism is postulated, based on current neurobiological knowledge, which makes it possible to account for self-consciousness as an epiphenomenon of language.