One-hundred and nine adult subjects were tested on two occasions using a set of computer administered letter series problems. Using methods introduced by Furneaux [In Eysenck, H. J. (Ed.), Handbook of abnormal psychology . New York: Basic Books, 1961], response times were analysed in order to provide estimates of item difficulties based on time to correct solution, rather than on probability of correct solution. Subject parameters of speed, continuance and accuracy were also calculated using both Furneaux (directly and indirectly) and classical methods. These ‘time based’ parameters were compared with subscale scores from the WAIS-R IQ test and parameters from two reaction time tasks: 1 and 2-bit choice reaction time and the ‘Odd-Man-Out’ task. It was concluded that the original Furneaux model performed sub-optimally with regard to parameter estimation. However, with some modifications made to these estimation procedures, the Furneaux parameters were shown to be both practical and useful estimates of subject performance on letter series problems.

A group of 113 smokers of normally distributed IQ was tested on two occasions on a choice reaction time task and the newly introduced ‘odd-man-out’ task. Performance on these two tasks was found to correlate significantly with IQ and personality variables as measured by the WAIS-R intelligence test and the EPQ and IVE. The effect of smoking on these tasks was also measured giving significant improvement in performance on both the reaction time tasks. Reliabilities were found for the reaction time parameters, and the effects of using reliabilities to ‘correct’ correlations is demonstrated. The validity of the commonly used correction for attenuation due to restricted IQ range on the performance x IQ correlation was also investigated. The effect of smoking on reaction times is discussed in relation to Knott's “gate theory”.

A sample of adult Ss of reasonably normal intelligence were given an ‘IQ’ test, a series of RT tests using 0, 1, 2, 3 bits of information in a Hick paradigm and an RT task requiring choice of 1 of 3 lights as an ‘odd-man-out’ on the basis of its relative position. Negative correlations were found between both RT and measures of variation in RT and ‘IQ’ for both of the two tasks. Recent results showing no correlation between Hick slope and ‘IQ’ and no increase in correlation between ‘IQ’ and RT with increasing number of bits, are confirmed. An explanation for findings of Ss whose RT data do not conform to Hick's law is tested and found inadequate. The ‘odd-man-out’ task is found to show an effect of ‘learning’ across the period of the task, the size of the learning effect was found also to correlate with ‘IQ’, but no evidence for learning was found with the choice RT task.