Blinded by headlights.

Target identification is impaired when targets are presented during the planning or execution of a compatible response (e.g., right-pointing arrow during a right keypress) relative to an incompatible response (Müsseler & Hommel, 1997 a, b). Examinations of this blindness to response-compatible stimuli have typically used arrowheads as targets ("<" and ">"). The importance of the target symbol was examined by manipulating subjects' interpretation of that symbol (i.e., ">" interpreted as a right-pointing arrow or as a headlight shining to the left). Targets were presented at varying times during the planning or execution of a response in order to examine the time-course of the effect. Results showed that the interpretation, and not the physical identity, of the target was important for the blindness effect. Although the blindness effect was largest during the planning and execution of a response, it was not always confined to that temporal interval.     

Induction by reinforcer schedules.

Traditional strategies for determining whether a reinforcer schedule enhances the occurrence of an activity are reviewed and critically evaluated. A basic assumption underlying these strategies is that it is possible to isolate the effect of reinforcer intermittency on schedule induction. It is concluded that this is not, in fact, possible. An alternative approach is proposed that emphasizes the inductive effects of the reinforcer schedule as a unit and the effects of particular aspects of the reinforcer schedule (e.g., interreinforcer interval, repetition of the reinforcer, reinforcer magnitude).