The target paper by Barba (2012) raises issues that were the focus of the author's first two publications on operant variability. The author will describe the main findings in those papers and then discuss Barba's specific arguments. Barba has argued against the operant nature of variability. (Contains 2 figures.)

In his article, the author claimed that studies of operant variability that use a lag-"n" or threshold procedure and measure the obtained variability through the change in U value fail to provide direct evidence that variability is an operant dimension of behavior. To do so, he adopted Catania's (1973) concept of the operant, which takes the…

The purpose of the current investigation was to quantify the quality of various verbal items on a college population that was voluntarily involved in remedial training in the basic academic skills. (Author)

To examine the effects on concurrent performance of independent manipulations of response-unit duration and number, 6 hens were exposed to concurrent second- order schedules of reinforcement. Each first-order operant unit required completion of a fixed-ratio schedule within the time specified by a fixed- interval schedule, with one further…

The purpose of the present study was to investigate more directly the effects of content and repetition of contingent visual feedback on a discrete operant pulling response and accompanying visual attention in 24 six- to seven-month old infants. Simultaneous recording was made of infant operant behavior and visual attention. Results indicated…