Divergent effects of healthy ageing on semantic knowledge and control: Evidence from novel comparisons with semantically impaired patients

Effective use of semantic knowledge requires a set of conceptual representations and control processes which ensure that currently relevant aspects of this knowledge are retrieved and selected. It is well-established that levels of semantic knowledge increase across the lifespan. However, the effects of ageing on semantic control processes have not been assessed. I addressed this issue by comparing the performance profiles of young and older people on a verbal comprehension test. Two sets of variables were used to predict accuracy and RT in each group: (1) the psycholinguistic properties of words probed in each trial and (2) the performance on each trial by two groups of semantically impaired neuropsychological patients. Young people demonstrated poor performance for low-frequency and abstract words, suggesting that they had difficulty processing words with intrinsically weak semantic representations. Indeed, performance in this group was strongly predicted by the performance of patients with semantic dementia, who suffer from degradation of semantic knowledge. In contrast, older adults performed poorly on trials where the target semantic relationship was weak and distractor relationships strong – conditions which require high levels of controlled processing. Their performance was not predicted by the performance of semantic dementia patients, but was predicted by the performance of patients with semantic control deficits. These findings indicate that the effects of ageing on semantic cognition are more complex than has previously been assumed. While older people have larger stores of knowledge than young people, they appear to be less skilled at exercising control over the activation of this knowledge.     

Perceptions of Liver Transplant Candidates with or Without an Alcohol Use History

Cirrhosis secondary to alcohol use is a primary cause of liver disease and a medical condition for which liver transplantation is a viable treatment option. However, there remains considerable debate within both the lay and the medical communities regarding the distribution of a scarce medical resource to adults with alcoholism. This study examined college students' perceptions toward an adult, presented in a written vignette, for whom liver transplantation was medically indicated. The influence of gender (female and male) and alcohol use history (no alcohol history, alcoholism history with long-term abstinence, alcoholism history with current use) on these ratings was examined. Subjects rated the adult presented with no alcohol history more positively than they did the adults presented with a history of alcoholism. Also, the adult with no alcohol history was more likely to be offered transplantation and was given higher priority ratings for transplantation by subjects. While subjects' own alcohol use history and organ donor registration status were not associated with ratings, having a family member with an alcohol problem and personally knowing a transplant recipient were related to more favorable ratings toward the adult presented in the vignette. Implications of these findings as well as limitations of the study are discussed.     

Recalling more childhood events leads to judgments of poorer memory: Implications for the recovered/false memory debate

Dissociative disorders that are believed to develop from childhood sexual abuse are often considered to include amnesia for childhood events, particularly the events that involve the abuse itself. One unresolved issue is the extent to which memory recovery attempts can contribute to claims of having amnestic symptoms. Experiments with undergraduate subjects reveal that requiring more reports of childhood events will increase judgments of having poorer memory of one’s childhood. The results are consistent with the use of heuristics when one is reasoning under conditions of uncertainty, as experienced difficulty in remembering more experiences is attributed to the incompleteness of childhood memory. The findings challenge the validity of reports of childhood amnesia that follow memory recovery attempts.     

Persistence of acquired behavioral control in the context of imprinting

Newly hatched Khaki Campbell ducklings (Anas platyrhynchos domesticus) were exposed to a moving object that immediately suppressed distress vocalizations occurring in a novel environment. The static visual and auditory features of this object acquired the ability to suppress distress vocalizations after eight 20-min sessions of exposure to the object in motion. The acquired suppressive properties of these features were found to persist throughout thirty 20-min sessions given over 10 days. During these sessions, the ducklings were continually exposed to the static features in the absence of visual movement. In a second experiment, the ability of these features in the absence of visual movement. In a second experiment, the ability of these features to serve as reinforcement for a pecking response was shown to persist for up to 56 hr. In one duckling, presentations of the static visual features did not maintain pecking behavior. However, it was shown that pecking responses could be re-instated in this duckling by introducing novel stimuli to the environment.     

Semantic memory for metaphor: The conceptual base hypothesis

The idea that people can encode and use an extremely abstract and general form of a complex linguistic (proverb) input-a conceptual base-was examined in two experiments. In Experiment I, each proverb was accompanied by either a conceptually related (good, mediocre, or poor) or an unrelated interpretation. The related interpretations were more effective recall prompts than were the unrelated interpretations, but only for high-imagery proverbs. In Experiment II, subjects wrote interpretations of the proverbs and then received either the proverb subject-noun or a brief story as a prompt. As was the case for the interpretations in Experiment I, the stories did not share any major vocabulary or propositional structure with their proverb source. Nonetheless, the stories were as effective as the nouns. Also, quality of proverb interpretation and of recall performance were positively related, with the correlations involving low-imagery proverbs, and stories, tending to be higher. Both experiments provided support for the conceptual-base notion, and underlined the importance of interpretive context, but more definitive evidence is needed.     

Partial differential feedback: An on-line training configuration for the optimization of multidimensional cue learning

The present paper describes a PDP-9 computer configuration arranged for experimental research into the acquisition of judgmental skill, but designed to overcome certain deficiences noted in stimulus-response-outcome (SRO) paradigms. The configuration departs radically from traditional approaches in that (a) the stimulus is placed under S control; (b) the requirement for a “response” is eliminated; (c) outcome feedback is a continuously changing function of the multiattribute stimulus settings under the control of S; and (d) the configuration makes possible the rapid learning of an essential feature of such learning tasks, namely the partial derivatives of the criterion or outcome variable with respect to each of the stimulus attributes.