Switching tasks and attention policies

The determinants and costs of control were studied in 6 experiments examini ng the performance costs of changing stimulus dimension (digit value/number of elements) or attention strategies (speed/accuracy) on the first trial a fter task transition. Costs were compared for task shift and reconsideratio n only. preparation ability was studied by presenting all transition inform ation at the beginning of a a-part block or only prior to each part. Result s showed pronounced first-trial transition costs. Different factors were as sociated with stop-start and task-switching requirements. Transition costs were separate from those of basic task performance. Costs were sensitive to global control considerations and were larger for task dimension changes t han for attention strategy shifts. Costs involving task dimension change, b ut not strategy shifts, were reduced with advanced preparation. These resul ts are discussed in relation to contemporary models of control. A new disti nction is proposed between activation and execution of control strategies.