Psychological Review

Chappell, M. N.; Pike, F. H.

doi: 10.1037/h0058045pmid: N/A

Two lines of development in neurophysiology seem to have particular significance for the problem of learning: (1) the changes in the functional capacity of a conduction system, and (2) summation of stimuli. Evidence from observations made by the authors and a number of other investigators supports the theory that the functional capacity of conduction systems is enlarged by use, just as in the case of muscle tissue. The phenomena of summation of stimuli, including the special case of summation at a synapse, of impulses from many converging systems are well supported. Probably chemical excitants within the neural system can produce summation phenomena as well as peripheral excitations. These facts throw light on the learning process because they explain how a few sources of excitation can acquire the power to initiate a response which originally required a number of sources. It accounts for the conditioned response and for the effects of repetition in practice, though it fails to explain some learning phenomena.

Hamilton, J. A.

doi: 10.1037/h0063095pmid: N/A

No reliable evidence has been found for a relationship between special or general intelligence and the physical characteristics, e.g., size, weight, etc., of the human brain. Attempts to measure the brain indirectly by cranial measurements have yielded very low positive correlations (of the order of .05 to .10) with intelligence. It is concluded that individual differences in intelligence are determined either by some physical factor or factors as yet undiscovered or by such a multiplicity of factors as to defy analysis.

Holway, A. H.; Pratt, C. C.

doi: 10.1037/h0059748pmid: N/A

Results of psychophysical research show the Weber ratio (|DR/R) to be a specific, dependent and reproducible function of R in every particular instance. In all cases, as R increases, |DR/R decreases and approaches a minimal value. In most cases |DR/R as a function of R tends to pass through this minimum and then rise. Two important psychophysical factors are discussed: (1) the distinction between |DR as mean j.n.d. and |DR as variation index, and (2) the need for an exact understanding of the relation which may exist between the two types of |DR The stimulus to sensory intensity is generalized for all sensory mechanisms in terms of the fundamental dimension of the stimulus (F), the unit designated the "Fechner." The general properties of W, the Weber ratio that depends on |DR as mean j.n.d., have been defined for any particular sensory system and for all values of F

Woodrow, H.

doi: 10.1037/h0057376pmid: N/A

Through variations in number and spatial separation, five widely different degrees of difficulty were given to the task of naming letters presented tachistoscopically for 0.1 sec. Sums were obtained from 168 university students tested individually under each of the five sets of conditions, whose difficulty was then determined by two different methods. One yields a measure of difference in terms of the standard deviation of the difficulty of the task performance under one set of conditions. The other assumes that the relation between the average percent correct score and the difficulty of the conditions may be represented by the normal distribution curve, whose ordinates indicate the average percentage correct scores and whose abscissae indicate the inverse of the difficulty of the conditions resulting in those average scores. The two methods gave results in substantial agreement. A third method usable under certain conditions is described. All three may be applied to the scaling either of difficulty or of ability.

Hilgard, E. R.

doi: 10.1037/h0058976pmid: N/A

Theories of conditioning fall into two types: (1) those which attempt to explain the facts of conditioning, and (2) those attempting to deduce other types of behavior, such as familiar forms of learning, from the facts of conditioning. The first are called theories of conditioning; the second, theories of learning (etc.) based on conditioning. In working with the concept of conditioning, some authors have conceived of it in terms of stimulus substitution, while others, mainly critics, have attempted to view the facts organismically. The stimulus-substitution formula is given support by many descriptive facts of conditioning, including some which are supposed to contradict it, such as the change in latent time, amplitude and some kinds of configurational change of the conditioned response. But other kinds of configurational change, such as those involved in conditioned breathing, are opposed to it. Neither does it explain the fact that succession of stimuli is more favorable than simultaneity, nor the tendency toward extinction of conditioned responses when not reinforced.