Abstract
Perception and identification of visual stimuli improve with experience. This applies to both simple stimuli and complex objects, as shown in perceptual learning paradigms in which visual perception is challenged by degrading the stimuli, e.g. by backward masking or adding simultaneous noise. In each of these paradigms, perceptual learning is specific for the stimuli used during training. However, there can also be differences between paradigms, because they challenge the visual processing system in different ways. It is thus possible that paradigm-specific processes are needed to optimize performance. This would result in a failure of perceptual learning effects to generalize across paradigms. Here we present the first study designed to investigate whether visual object learning is specific to the type of stimulus degradation used during training. Sixteen participants were trained to recognize and name pictures of common objects. The stimulus set included 40 object images, but each participant was trained on only half of them. Half of the participants was trained in a backward masking paradigm, and the other half in a simultaneous noise addition paradigm. After five days, performance thresholds were measured in four tests: (1) the trained paradigm with the 20 trained objects, (2) the trained paradigm with the 20 new, untrained objects, (3) the untrained paradigm with the trained objects and (4) the untrained paradigm with new objects. Both groups showed a learning effect that increased gradually across days. These training effects were specific for the trained objects. In addition, an object-specific transfer to the untrained paradigm was found. The group trained in the simultaneous noise addition paradigm showed a complete transfer of performance to the backward masking task. The transfer was only partial when reversed. These findings indicate that both general learning processes and processes specific for the type of stimulus degradation are involved in perceptual learning.
This work was supported by the Research Council of K.U.Leuven (CREA/07/004), the Fund for Scientific Research – Flanders (1.5.022.08), and by the Human Frontier Science Program (CDA 0040/2008).