Performing prototype distortion tasks requires no contribution from the explicit memory systems: evidence from amnesic MCI patients in a new experimental paradigm

How do irrelevant stimuli from another modality influence responses to the targets in a same-different task

It remains unclear whether multisensory interaction can implicitly occur at the abstract level. To address this issue, a same-different task was used to select comparable images and sounds in Experiment 1. Then, the stimuli with various levels of discrimination difficulty were adopted in a modified same-different task in Experiments 2, 3, and 4. The resultsshowed that only when the irrelevant stimuli were easily distinguishable, aconsistency effectcould beobservedin the testing phase. Moreover, when easily distinguishableirrelevant stimuliwere simultaneously presented with difficulttarget stimuli, irrelevant auditorystimuli facilitated responses to visual targets whereas irrelevant visual stimuli interfered with responses to auditorytargetsin the training phase,indicating an asymmetry in the role of visual and auditory in abstract multisensory integration. The results suggested that abstract multisensory information could be implicitly integrated and the inverse effectiveness principle might not apply to high-level processing of abstract multisensory integration.

Multisensory Information Facilitates the Categorization of Untrained Stimuli

Although it has been demonstrated that multisensory information can facilitate object recognition and object memory, it remains unclear whether such facilitation effect exists in category learning. To address this issue, comparable car images and sounds were first selected by a discrimination task in Experiment 1. Then, those selected images and sounds were utilized in a prototype category learning task in Experiments 2 and 3, in which participants were trained with auditory, visual, and audiovisual stimuli, and were tested with trained or untrained stimuli within the same categories presented alone or accompanied with a congruent or incongruent stimulus in the other modality. In Experiment 2, when low-distortion stimuli (more similar to the prototypes) were trained, there was higher accuracy for audiovisual trials than visual trials, but no significant difference between audiovisual and auditory trials. During testing, accuracy was significantly higher for congruent trials than unisensory or incongruent trials, and the congruency effect was larger for untrained high-distortion stimuli than trained low-distortion stimuli. In Experiment 3, when high-distortion stimuli (less similar to the prototypes) were trained, there was higher accuracy for audiovisual trials than visual or auditory trials, and the congruency effect was larger for trained high-distortion stimuli than untrained low-distortion stimuli during testing. These findings demonstrated that higher degree of stimuli distortion resulted in more robust multisensory effect, and the categorization of not only trained but also untrained stimuli in one modality could be influenced by an accompanying stimulus in the other modality.

Evidence of stable individual differences in implicit learning

There is a fundamental psychological and neuropsychological distinction between explicit and implicit memory, and it has been proposed that whereas there are stable trait individual differences in explicit memory ability, there are not such differences across people for implicit learning. There is, however, little evidence about whether or not there are stable trait differences in implicit learning. Here we performed a test-retest reliability study with healthy young adults in which they performed four implicit learning tasks (artificial grammar learning, probabilistic classification, serial response, and implicit category learning) twice, about a week apart. We found medium (by Cohen's guidelines) test-retest reliability for three of the tasks: probabilistic classification, serial response, and implicit category learning, suggesting that differences in implicit learning ability are more stable than originally thought. In addition, implicit learning on all tasks was unrelated to explicit measures: we did not find any correlation between implicit learning measures and independent measures of IQ, working memory, or explicit learning ability. These findings indicate that implicit learning, like explicit learning, varies reliably across individuals.

Which Matters More in Incidental Category Learning: Edge-Based Versus Surface-Based Features

Although many researches have shown that edge-based information is more important than surface-based information in object recognition, it remains unclear whether edge-based features play a more crucial role than surface-based features in category learning. To address this issue, a modified prototype distortion task was adopted in the present study, in which each category was defined by a rule or a similarity about either the edge-based features (i.e., contours or shapes) or the corresponding surface-based features (i.e., color and textures). The results of Experiments 1 and 2 showed that when the category was defined by a rule, the performance was significantly better in the edge-based condition than in the surface-based condition in the testing phase, and increasing the defined dimensions enhanced rather than reduced performance in the edge-based condition but not in the surface-based condition. The results of Experiment 3 showed that when each category was defined by a similarity, there was also a larger learning effect when the category was defined by edge-based dimensions than by surface-based dimensions in the testing phase. The current study is the first to provide convergent evidence that the edge-based information matters more than surface-based information in incidental category learning.

Early detection of memory impairments in older adults: standardization of a short version of the verbal and nonverbal Recognition Memory Test

In several neurological conditions, in elderly and cognitively impaired subjects, memory functioning must be evaluated to early detect the cognitive deterioration processes. In particular, recognition memory assessment is an essential step in the clinical and neuropsychological evaluation of early memory impairments. The Recognition Memory Test (RMT) developed by Smirni et al. (G Ital Psicol XXXVII(1):325-343, 2010) is an effective instrument to assess verbal and nonverbal recognition memory in the Italian population. The current study provides a new, brief, and reliable RMT format to evaluate recognition memory on elderly subjects and it reports normative data in an older adult Italian population sample (including 100 participants well distributed across sex, education, and age categories). The shortened version of RMT keeps the administration procedures and materials of the original Italian RMT constant, i.e., words, faces, and buildings. Multiple regression analysis revealed significant effects of age and educational level on performance but no effect of sex. Inferential cutoffs have been determined and equivalent scores computed. The availability of equivalent scores for the Recognition Memory Test will prove useful in the clinical evaluation of patients' memory profiles.