Leigh M. Riby

The effects of age and task domain on dual task performance: A meta-analysis

Recent research has provided mixed findings as to whether older adults find dual tasking problematic. Here, we examined whether methodological variations across studies can account for the discrepancies in the literature. Meta-analyses conducted on the results of 34 studies conducted between 1981 and 2003 found a strong overall effect size (d = .68), which indicated a clear age-related dual tasking impairment. However, this effect size was not representative of all the individual studies reported. Subsequent analyses, using an analysis of variance analogue (Hedges & Olkin, 1985), investigated potential moderators responsible for the variability in the effect sizes across studies. These secondary analyses included a comparison of dependent measure used, whether baseline differences in performance had been controlled for, and task domain. Task domain was found to be the critical moderator variable. Notably, tasks with a substantial controlled processing, or motor component showed greater dual task impairment than tasks that were relatively simple or relied on automatic processing.

The facilitative effects of glucose ingestion on memory retrieval in younger and older adults: Is task difficulty or task domain critical?

The ingestion of a glucose-containing drink has been shown to improve cognitive performance, particularly memory functioning. However, it remains unclear as to the extent to which task domain and task difficulty moderate the glucose enhancement effect. The aim of this research was to determine whether boosts in performance are restricted to particular classes of memory (episodic v. semantic) or to tasks of considerable cognitive load. A repeated measures (25 g glucose v. saccharin), counterbalanced, double-blind design was used with younger and older adults. Participants performed a battery of episodic (e.g. paired associate learning) and semantic memory (e.g. category verification) tasks under low and high cognitive load. Electrophysiological measures (heart rate and galvanic skin response) of arousal and mental effort were also gathered. The results indicated that whilst glucose appeared to aid episodic remembering, cognitive load did not exaggerate the facilitative effect. For semantic memory, there was little evidence to suggest that glucose can boost semantic memory retrieval even when the load was manipulated. One exception was that glucose facilitated performance during the difficult category fluency task. Regardless, the present findings are consistent with the domain-specific account in which glucose acts primarily on the hippocampal region, which is known to support episodic memory. The possible contribution of the hippocampus in semantic memory processing is also discussed.

The effects of music exposure and own genre preference on conscious and unconscious cognitive processes: A pilot ERP study

Did Beethoven and Mozart have more in common with each other than Clapton and Hendrix? The current research demonstrated the widely reported Mozart Effect as only partly significant. Event-related brain potentials (ERPs) were recorded from 16 professional classical and rock musicians during a standard 2 stimulus visual oddball task, while listening to classical and rock music. During the oddball task participants were required to discriminate between an infrequent target stimulus randomly embedded in a train of repetitive background or standard stimuli. Consistent with previous research, the P3 and N2 ERPs were elicited in response to the infrequent target stimuli. Own genre preference resulted in a reduction in amplitude of the P3 for classical musicians exposed to classical music and rock musicians exposed to rock music. Notably, at the pre-attentive stage of processing (N2) beneficial effects of exposure to classical music were observed for both groups of musicians. These data are discussed in terms of short and long-term music benefits on both conscious and unconscious cognitive processes.

Memory processing and the glucose facilitation effect: The effects of stimulus difficulty and memory load

Abstract Previous research has consistently found enhancement of memory after the ingestion of a glucose containing drink. The aims of the present study were to specify more precisely the nature of this facilitation by examining the cognitive demand hypothesis. This hypothesis predicts greater glucose induced facilitation on tasks that require significant mental effort. In two experiments, both employing an unrelated sample design, participants consumed either 25 g of glucose or a control solution. In experiment 1, participants first studied low and high imagery word-pairs and memory was assessed 1-, 7- and 14-days later by cued recall. Overall, glucose enhanced both encoding and consolidation processes only for the more difficult low imagery pairs. In experiment 2, the degree of mental effort in a verbal memory task was manipulated in two ways: (1) by varying the phonological similarity of the words; and (2) by varying the length of word lists. Glucose was found to enhance memory only for longer word lists. These data are consistent with the idea that glucose is especially effective in demanding memory tasks, but place some limits on the forms of difficulty that are susceptible to enhancement.