Concurrent schedules of reinforcement: effects of gradual and abrupt increases in changeover delay

Pigeons' pecks were maintained on concurrent variable-interval 1-min variable-interval 3-min schedules of reinforcement, with a changeover delay of 2 sec. When changeover delay was increased successively to 5.0, 7.5, and 12.5 sec (Exp. I) the actual relative rate of reinforcement for the variable-interval 3-min key decreased progressively for two birds, abruptly for two other birds, and the subjects devoted proportionately less of their time and responding to that key. However, the relative performance measures (relative time and relative responding) approximated the actual relative rate of reinforcement, with a maximum discrepancy of 11%, over all changeover delay values investigated. Experiment II attempted to lengthen response-run durations on the variable-interval 3-min key so that they were long enough to meet the changeover delay requirement at each new changeover delay value, by progressively increasing the changeover delay by 0.5-sec increments. With this procedure the actual relative rate of reinforcement approximated more closely the scheduled relative rate as changeover delay increased. As in Exp. I, relative performance measures approximated the actual relative reinforcement rate (maximum discrepancy 17%).     

Infant search strategies with containers that move but do not alter the location at which contents can be found

A number of hypotheses about infants' delayed search accuracy have been based upon the notion that a location associated with repeated retrieval of the object attains privileged status. Infants may need strong cues to search at a new location. However, a test is reported in which performance of 12- and 15-month-old infants was shown to be indifferent to the location. The results were reliable at an individual level. The data accord with previous research upon the canonicality effect in infant spatial search, an effect which is taken to index an experiential constraint on spatial discrimination. The experimental design thus serves as a discriminative test between three approaches: the original privileged location hypothesis, a newer spatial-contrast hypothesis, and a wider approach which focuses on experiential constraints on learning, including the canonicality effect.     

Relevance of genotype and its environmental counterpart to the theory,interpretation, and nomenclature of ability measures

While the constructs of aplitude and achievement, which are here defined as genotypic and environmental constructs, are potentially useful in psychological theory and in the development of predictors and weights for predictors, the use of these terms for psychological tests is highly misleading. When used for tests, the terms lead to invalid inferences concerning the constructs and to erroneous predictions of later criteria. All psychological tests measure current performance levels which are phenotypic characteristics. Practically all such tests can be used to estimate both genotypic and environmental constructs with nonzero accuracy. The basic error is to use a term which denotes a genetic or an environmental construct for a phenotypic measure. Implications of this position for inferences concerning group differences in aptitude and for construct validity of tests are briefly discussed.     

Interfacing the DEC LPS 11 to electromechanical laboratory apparatus

A hardware-software extension to the DEC LPS 11 facilitates interfacing the PDP 11 to external instruments. The hardware component consists of eight relay drivers and relays, four contact conditioners, and an interrupt pulse former. FORTRAN-callable RT-11 MACRO subroutines control the device, service interrupts, and transfer control to FORTRAN completion routines.     

Causes of racial and socioeconomic differences in cognitive tests

Correlations among profiles of means based upon 75 cognitive variables from Project TALENT are presented for groups defined by race, socioeconomic status, sex, area of the country, and grade in high school. Sex makes by far the largest contribution to differences in shape of profiles. Race and socioenconomic status, in turn, make much larger contributions to differences than grade and area. Sex differences in shapes of profiles are a function primarily of race and, to a lesser extent, of social class. Race differences are larger than socioeconomic differences and the former, in particular, are also a function of sex. Black males differ more from white patterns than black females. There is lack of substantial overlap in the causes of race and socioeconomic differences in shape of cognitive profiles.     

An optically isolated digital interface for the SKED system

A digital interface to support the SKED software system in recent versions of the PDP-8 computer. One printed circuit card of interface logic and optical isolators can be installed in the OMNIBUS to provide 24 input and 36 output lines to external panels containing input simulation switches and input or output indicators.     

Piagetian tasks measure intelligence and intelligence tests assess cognitive development: A reanalysis

A reanalysis of the intercorrelations of Wechsler subtests, achievements tests, and Piagetian tasks originally published by Stephens et al. (1972) has corrected errors in the original design and has used models which allow both differences and similarities to appear. Unit weighted composites of the two sets of tests were formed after first partialling chronological age out of the complete table of intercorrelations. The correlation between the composites is .876 which corrects, using split-half estimates of reliabilities, to .918. Next the matrix of partial correlations was factored and the factors rotated to a hierarchical structure. Piagetian tasks contribute almost equally to the definition of the general factor in intelligence along with the Wechsler subtests and the achievement tests. The general factor, furthermore, makes the single largest contribution to the variance of most of the measures of both sets. The smaller group factors consist of an Academic Achievement factor and three Piagetian factors. Of the latter the largest and most clearly identified is the factor called Operational Thought in the earlier analysis, but is here described simply as Conservation. It is concluded that the evidence for communality in function far outweighs the differences between intelligence tests and Piagetian tasks.