In perceptual learning (line length/orientation discrimination, visual target detection, tone frequency discrimination, etc), when training people or animals to perform a task better, is there an optimal schedule for controlling task difficulty, to acheive maximal improvement?At least 3 reasonable schedules come to (my) mind:Easy to difficult - In education it is the custom to begin with easy examples or problems, and gradually progress to more difficult ones. Maybe this should work in perceptual learning as well.Interleave different difficultiesAlways the most difficult possibleHas there been a rigorous comparison of such schedules and their effect on the rate of learning, and the maximal performance level achieved at the end of training?
How does task difficulty schedule affect the rate and efficiency of perceptual learning?
perception;perceptual learning;training
General pedagogical ideas around optimal difficultyMany theories of instruction suggest that learning is optimal when an appropriate level of challenge is maintained. If a task is too easy, there's little to learn. If a task is too difficult, the learner can be overwhelmed. The implication for practice is that task difficulty should increase in conjunction with the increased skill of the learner. Of course, we can think of exceptions to these ideas, such as the value of over-learning, and the general idea of exposing people to challenging problems to motivate further learning. This also still leaves open the question of precisely how fast difficulty should increase for a given learner.Academically, I've seen these ideas expressed in several places:Deliberate practice: This is a concept drawn from the expertise literature. It is posited that amount of deliberate practice (rather than amount of simple experience) is one of the key factors that discriminates experts from non-experts (see Ericsson et al 2006). A key aspect of task difficulty relates to the sequencing of task difficulty with practice. Ericsson et al (2006) writes thatThe core assumption of deliberate practice ... is that expert  performance is acquired gradually and that effective improvement of  performance requires the opportunity to find suitable training tasks  that the performer can master sequentially... Deliberate practice  presents performers with tasks that are initially outside their  current realm of reliable performance, yet can be mastered within  hours of practice by concentrating on critical aspects and by  gradually refining performance through repetitions after feedback.Challenge point in motor learning:Guadagnoli and Lee present a framework for thinking about optimal difficulty in motor learning. Their framework suggests that optimal learning is achieved by maintaining task difficulty at the point where it provides optimal information (where learning is possible, but it is not too difficult as to be overwhelming).Research on task difficulty and perceptual learningIn a review article Ahissar and Hochstein (2004) also suggest easy to difficult is the most effective regime for perceptual learning:As found in our studies, training is more effective if subjects start  with easy conditions and gradually move to more difficult con-  ditions. The importance of beginning training with easy conditions was  first found by Pavlov. When Pavlov reinforced a dogs salivation  following its seeing an ellipse but not following its seeing a circle  (Figure I, rightmost pair of stimuli), the dog could not avoid  generalization and salivated at sight of the circle, as well. Only by  using very elongated ellipses, and training along the continuum, from  left to right, was it able to achieve good performance for small  circle/ellipse differences. This phenomenon was subsequently termed  transfer along a continuum (of different degrees of difficulty).ReferencesAhissar, M. and Hochstein, S. (2004). The reverse hierarchy theory ofvisual perceptual learning. Trends in cognitive sciences, 8(10):457-464. FREE PDFEricsson, K. et al. (2006). The influence of experience and deliberatepractice on the development of superior expert performance. TheCambridge handbook of expertise and expert performance, 10(3):683-703.FREE PDFGuadagnoli, M. and Lee, T. (2004). Challenge point: a framework forconceptualizing the effects of various practice conditions in motorlearning. Journal of Motor Behavior, 36(2):212-224. FREE PDF