A concurrent-chain procedure was used to study pigeons' choices between rewards differing in both amount and delay. The shorter delay terminated with a 2-second access to grain whereas the longer delay terminated with a 6-second access to grain. The ratio of the delays was constant within a given condition while their absolute values were varied. Over conditions, ratios of 6:1, 3:1, and 3:2 were studied. As the absolute values of the delays to reinforcement increased, preference for the longer-delayed but larger reward decreased under both the 6:1 and 3:1 ratios, but increased under the 3:2 ratio. These results are inconsistent with choice models predicting no change in preference when the ratios of delays and amounts are held constant. In addition, the change in preference under the 3:1 ratio is inconsistent with a simple multiplicative interaction of the trade off between reinforcer amount and delay, and suggests that delay is a more potent determinant of choice than is amount. These results have implications for models that view choice between small immediate rewards and large but delayed rewards as underlying the behavior commonly called self control.

Psychologists and educational specialists with expertise in areas related to intelligence testing responded to a questionnaire dealing with a wide variety of issues constituting the IQ controversy. Overall, experts hold positive attitudes about the validity and usefulness of intelligence and aptitude tests. Tests are seen as adequately measuring most important elements of intelligence, although the tests are believed to be somewhat racially and socioeconomically biased. There is overwhelming support for a significant within-group heritability for IQ and a majority of respondents feel that black-white and socioeconomic status IQ differences are also partially hereditary. Problems with intelligence tests are perceived in the influence of nonintellectual characteristics on test performance and in the frequent misinterpretation and overreliance on test scores in elementary and secondary schools. Despite these difficulties, experts favor the continued use of intelligence and aptitude tests at their present level. Variation in responding to substantive questions on testing is largely resistant to prediction by a host of demographic and background variables, including within-sample variation in expertise.

Eight pigeons responded under a concurrent-chain schedule for rewards differing in both delay and amount, the larger reward being associated with the longer delay. Preference was examined as the absolute durations of the terminal-link delays were increased at four different delay ratios. Difficulties with other experiments of this type were controlled for by the use of (a) a single-tape initial link to equalize terminal-link entries, (b) a blackout following the more immediate reward to equalize terminal-link length, and (c) a photocell to measure reinforcer duration more accurately. Preference for the larger reward changed systematically as delays increased in all conditions, decreasing for the 6:1, 3:1, and 3:2 ratios, and increasing for the 1:1 ratio. These results were similar to, but significantly different from, those of previous investigations. The implications of these results for various models of concurrent-chain behavior are discussed.

An adjusting procedure was used to measure pigeons' preferences among alternatives that differed in the duration of a delay before reinforcement and of an intertrial interval (ITI) after reinforcement. In most conditions, a peck at a red key led to a fixed delay, followed by reinforcement, a fixed ITI, and then the beginning of the next trial. A peck at a green key led to an adjustable delay, reinforcement, and then the next trial began without an ITI. The purpose of the adjusting delay was to estimate an indifference point, or a delay that made a subject approximately indifferent between the two alternatives. As the ITI for the red key increased from 0 s to 60 s, the green-key delay at the indifference point increased systematically but only slightly. The fact that there was some increase showed that pigeons' choices were controlled by more than simply the delay to the next reinforcer. One interpretation of these results is that besides delay of reinforcement, rate of reinforcement also influenced choice. However, an analysis that ignored reinforcement rate, but considered the delays between a choice response and the reinforcers on subsequent trials, was able to account for most of the obtained increases in green-key delays. It was concluded that in this type of discrete-trial situation, rate of reinforcement exerts little control over choice behavior, and perhaps none at all.

It is often claimed that the racially biased Immigration Act of 1924 was passed with the help of the intelligence testing community of the period. The claim consists of two components: first, that the intelligence testing community saw its test data on social and ethnic differences as favoring a discriminatory immigration policy and, second, that Congress relied to some significant extent on the testing community and/or its data. An examination of the historical record failed to uncover any support for either component of the claim. The testing community did not generally view its findings as favoring restrictive immigration policies like those in the 1924 Act, and Congress took virtually no notice of intelligence testing, as far as one can ascertain from the records and publications of the time.