Adult age differences in visual word identification: functional neuroanatomy by positron emission tomography

Adult age differences in the neural systems mediating semantic (context-independent) memory were investigated using positron emission tomography (PET). Younger (20-29 years) and older (62-70 years) participants performed lexical decision (word/nonword discrimination) and nonsemantic (simple visual search) baseline tasks during PET scanning. Within the lexical decision task, display duration and presentation rate were varied across scans. The behavioral data suggested that although an age-related slowing was evident in visual feature and response processing, the retrieval of semantic/lexical information was similar for younger and older adults. For both age groups, lexical-related activation occurred in inferior prefrontal and occipitotemporal regions of the left hemisphere. Differential activation, as a function of age group, was observed in the left occipitotemporal pathway as a result of older adults' maintaining higher levels of neural activity in striate cortex (during visual search) and in inferior temporal cortex (during lexical decision). The prefrontal activation was similar for the two age groups. Thus, although this form of semantic memory retrieval does not undergo significant age-related decline, an age-related change in the associated pattern of neural activation is evident. These findings differ from previous neuroimaging studies of episodic (context-dependent) memory retrieval, which have suggested that age-related compensatory mechanisms are expressed primarily by greater activation of prefrontal regions for older adults than for younger adults.     

Aging and attentional guidance during visual search: functional neuroanatomy by positron emission tomography

Positron emission tomography (PET) was used to examine adult age differences in neural activation during visual search. Target detection was less accurate for older adults than for younger adults, but both age groups were successful in using color to guide attention to a subset of display items. Increasing perceptual difficulty led to greater activation of occipitotemporal cortex for younger adults than for older adults, apparently as the result of older adults maintaining higher levels of activation within the easier task conditions. The results suggest that compensation for age-related decline in the efficiency of occipitotemporal cortical functioning was implemented by changes in the relative level of activation within this visual processing pathway, rather than by the recruitment of other cortical regions.     

Individual differences in phonological learning and verbal STM span

A relationship between phonological short-term memory tasks (e.g., nonword repetition, digit span) and vocabulary learning in both experimental and real-life conditions has been reported in numerous studies. A mechanism that would explain this correlation is, however, not known. The present study explores the possibility that it is the quality of phonological representations that affects both short-term recall and long-term learning of novel wordlike items. In Experiment 1, groups with relatively good and poor span for pseudowords were established. The good group was found to perform better at explicit memory tasks tapping the incidental learning of a limited stimulus pool used in an auditory immediate serial pseudoword recall task. In Experiment 2, the results of Experiment 1 were replicated when experience of correct recall was controlled. In Experiment 3, the immediate recall performance of the good group was found to benefit more than that of the poor group from syllable repetition within stimulus pools. It is concluded that the efficiency of a process that creates phonological representations is related both to short-term capacity for verbal items, and to long-term phonological learning of the structure of novel phonological items.     

Gender schemas and the salience of gender: Individual differences in nonreversal discrimination learning

Sixty-seven 3–6-year-old children, identified as gender schematic and aschematic, completed a nonreversal discrimination learning task. This task permits examination of children's abilities to attend selectively to particular dimensions of a multidimensional stimulus. Gender typing and size of stimulus were the relevant target dimensions. Gender schematic children required significantly more trials to criterion when the shift was from sex type to size of stimulus, and significantly fewer trials to criterion when the shift was from size to sex type of stimulus, than did aschematic children. Gender aschematic children's performance was relatively unaffected by type of stimulus dimension. Results support predictions of the differential salience of the gender dimension to gender schematic and aschematic children.     

Individual differences in the verbal coding of familiar visual stimuli

Two experiments were performed both of which involved the same-different comparison of pairs of alphabet letters. "Same" reaction times were obtained for both physical matches (e.g., AA) and name matches (e.g., aA). The results of both experiments supported the hypothesis that individual subjects would differ with respect to whether or not they based their physical matches on a comparison of verbal codes. In Experiment I, subjects differed in the size of their reaction time difference between physical and name matches, and in Experiment II, individuals differed with respect to whether or not the frequency of usage of the letters affected their reaction time for physical matches. In both experiments, the individual differences in verbally coding physical matches were related to Hock's (1973) individual differences distinction between subjects emphasizing analytic processes and subjects emphasizing structural processes.     

Frequency and coding responses in verbal discrimination learning

Ss were given a verbal discrimination task where correct and incorrect stimuli appeared in one, two. or four different pairs in a within-Ss design. For a group tested with the usual anticipation procedure, correct repetitions helped and incorrect repetitions hurt performance. The pattern of results suggested that frequency is a salient cue in verbal discrimination learning but that coding or paired-associate processing may occur at the same time. Data from a second group of Ss for which frequency was a less salient cue gave more direct evidence for coding.     

Imagery and sentence mediators in verbal discrimination learning

The effect of instructions to use imagery and sentence strategies in verbal discrimination learning (VDL) was investigated in two experiments. In Experiment I, both imaging to and constructing a sentence for the correct item of each pair facilitated VDL relative to an uninstructed control condition. Incorporating both words of the pair into a compound image or compound sentence had no effect, a result that was replicated in Experiment It. Of the two compound instructions, only compound sentences consistently facilitated associative recall of the VDL pairs, suggesting that compound imagery instructions were not always adhered to by the Ss.     

Individual differences in visual discrimination of letters.

Research on the distinctive features of letters has been inconclusive. Investigators may have overlooked individual variations in their data which would have supported feature-extraction hypotheses but were concealed by analyses which averaged data into group means. Response latencies from a matching discrimination task with the 26 English capital letters were analyzed with INDSCAL, a multidimensional scaling procedure which weights individual contributions to a psychological space. Underlying a dimensions were linearity, curvature, angularity, and closure. The solution disclosed that individuals utilized these features differentially in the visual discriminations. The results suggest that future research in visual feature extraction will benefit from the examination of individual variations in the perceptual process.     

Cue selection in verbal discrimination learning of retarded subjects.

A series of experiments was conducted to examine cue function in trigram verbal discrimination learning by retarded subjects. The issue was to determine the factors that control attention in this type of learning situation. The two variables of chief interest were trigram meaningfulness and reinforcement history. The major general conclusion was that retarded subjects employ complex cue selection strategies in solving a verbal discrimination involving compound verbal stimuli. Major findings were as follows: (a) Retarded subjects exhibit a response bias in favor of words over nonsense trigrams; (b) relatively little active cue selection based on meaningfulness was observed; (c) a compound stimulus discrimination was more difficult to learn than a discrimination involving single verbal stimuli; (d) compound and single stimuli may be processed differently in original discrimination learning; (e) cue position probably controls attention in compound discrimination learning; and (f) a frequency theory of verbal discrimination learning is supported by these data.     

Individual differences and informal learning in the workplace

Informal learning is important in today's dynamic and competitive business environment. However, research on informal learning is limited and largely anecdotal. Based on theory and research on training and development and positive psychology, this study examined the influence of individual differences including the Big Five personality dimensions, generalized self-efficacy, and zest on informal learning. One hundred eighty managers from an organization that owns and operates casual theme restaurants completed online measures of individual differences and informal learning approximately one year apart. The results demonstrated that each of the individual differences had a significant relationship with informal learning. However, zest was the only significant predictor of informal learning when all of the individual differences were considered together. The implications of the results for research and practice are discussed.     

Individual differences and informal learning in the workplace

Informal learning is important in today's dynamic and competitive business environment. However, research on informal learning is limited and largely anecdotal. Based on theory and research on training and development and positive psychology, this study examined the influence of individual differences including the Big Five personality dimensions, generalized self-efficacy, and zest on informal learning. One hundred eighty managers from an organization that owns and operates casual theme restaurants completed online measures of individual differences and informal learning approximately one year apart. The results demonstrated that each of the individual differences had a significant relationship with informal learning. However, zest was the only significant predictor of informal learning when all of the individual differences were considered together. The implications of the results for research and practice are discussed.     

Individual differences in verbal conditioning, extinction, and awareness

The present study examined the relationship of three individual difference variables—need for approval, a belief in internal versus external control of reinforcement, and verbal intelligence— to acquisition, extinction, and awareness in a verbal conditioning task Based on a postexperiment interview and recognition task, subjects were grouped according to their awareness of the response-reinforcement contingencies and the degree to which they admitted influence by the experimenter Approval motivated subjects were more likely to acquire the reinforced response regardless of awareness levels than were low need for approval subjects. Subjects assessed as internal were more likely to deny influence by the experimenter and in some instances were more resistant to extinction than subjects called external Subjects higher in verbal intelligence evidenced more awareness than subjects with lower intelligence scores Results suggest that the inclusion of individual difference variable is of crucial importance to a clear understanding of the experimenter-subject interaction in the verbal conditioning situation Implications for the other dyadic interactions, particularly psychotherapy, were discussed     

Sex differences in discrimination reversal learning in the guppy

In several mammalian and avian species, females show a higher performance than males in tasks requiring cognitive flexibility such as the discrimination reversal learning. A recent study showed that female guppies are twice as efficient as males in a reversal learning task involving yellow–red discrimination, suggesting a higher cognitive flexibility in female guppies. However, the possibility exists that the superior performance exhibited by females does not reflect a general sex difference in cognitive abilities, but instead, is confined to colour discrimination tasks. To address this issue, we compared male and female guppies in two different discrimination reversal learning tasks and we performed a meta-analysis of these experiments and the previous one involving colour discrimination. In the first experiment of this study, guppies were tested in a task requiring them to learn to select the correct arm of a T-maze in order to rejoin a group of conspecifics. In experiment 2, guppies were observed in a numerical task requiring them to discriminate between 5 and 10 dots in order to obtain a food reward. Although females outperformed males in one condition of the T-maze, we did not find any clear evidence of females’ greater reversal learning performance in either experiment. However, the meta-analysis of the three experiments supported the hypothesis of females’ greater reversal learning ability. Our data do not completely exclude the idea that female guppies have a generally higher cognitive flexibility than males; however, they suggest that the size of this sex difference might depend on the task.     

Individual differences in metacontrast masking are enhanced by perceptual learning

In vision research metacontrast masking is a widely used technique to reduce the visibility of a stimulus. Typically, studies attempt to reveal general principles that apply to a large majority of participants and tend to omit possible individual differences. The neural plasticity of the visual system, however, entails the potential capability for individual differences in the way observers perform perceptual tasks. We report a case of perceptual learning in a metacontrast masking task that leads to the enhancement of two types of adult human observers despite identical learning conditions. In a priming task both types of observers exhibited the same priming effects, which were insensitive to learning. Findings suggest that visual processing of target stimuli in the metacontrast masking task is based on neural levels with sufficient plasticity to enable the development of two types of observers, which do not contribute to processing of target stimuli in the priming task.