Age differences in working memory tasks: The role of secondary memory and the central executive system

Two experiments are reported in which age differences in working memory performance are explored. In the first study, young and older adults held 2, 3, 4, or 5 unrelated words in mind while verifying a single or complex sentence. An age-related decrement was found in subsequent serial recall of the words, and this decrement was larger with longer word lists. Experiment 2 confirmed the interaction between age and list length, using list lengths of 4, 6, and 8 words and a free-recall procedure. There was no interaction between age and divided attention in either experiment. Surprisingly, sentence complexity had a greater detrimental effect on recall in the younger group. The results are discussed in terms of articulatory rehearsal being augmented by using secondary memory in the case of younger subjects.     

Orientation Invariance and Geometric Primitives in Shape Recognition

Although it is generally assumed that vision is orientation invariant, that is, that shapes can be recognized regardless of viewing angle, there is little evidence that speaks directly to this issue, and what evidence there is fails to support orientation invariance. We propose an explanation for the previous results in terms of the kinds of shape primitives used by the visual system in achieving orientation invariance: Whereas contours are used at stages of vision that ore not orientation invariant, surfaces and/or volumes are used at stages of vision that are orientation invariant. The stimuli in previously reported studies were wire forms, which can represented only in terms of contour. In four experiments, testing both short-term and long-term memory for shape, we replicated the previous failures of orientation invariance using wire forms, but found relatively good or perfect orientation invariance with equivalently shaped surfaces.