Karen R. Brandt

Measuring the speed of the conscious components of recognition memory: remembering is faster than knowing

Three experiments investigated response times (RTs) for remember and know responses in recognition memory. RTs to remember responses were faster than RTs to know responses, regardless of whether the remember-know decision was preceded by an old/new decision (two-step procedure) or was made without a preceding old/new decision (one-step procedure). The finding of faster RTs for R responses was also found when remember-know decisions were made retrospectively. These findings are inconsistent with dual-process models of recognition memory, which predict that recollection is slower and more effortful than familiarity. Word frequency did not influence RTs, but remember responses were faster for words than for nonwords. We argue that the difference in RTs to remember and know responses reflects the time taken to make old/new decisions on the basis of the type of information activated at test.

The effect of glucose administration on the emotional enhancement effect in recognition memory.

Previous research has demonstrated that glucose administration improves memory performance. However few studies have addressed the effects of glucose on emotional material that by nature already enjoys a memory advantage. The aim of the present research was therefore to investigate whether the memory facilitation effect associated with glucose would emerge for emotional words. Experiment 1 demonstrated that negative words were better recognized and remembered than positive and neutral words. Experiment 2 further explored these effects under conditions of glucose administration and an aspartame control. The results revealed that both the aspartame and glucose groups replicated the results from Experiment 1. The present research therefore demonstrated that the glucose facilitation effect did not emerge for material that already benefits from a memory advantage. These results also raise the question of whether the dose response relationship previously associated with glucose administration is applicable when the information being processed is of an emotional nature.

The effects of glucose dose and dual task performance on memory for emotional material.

Whilst previous research has shown that glucose administration can boost memory performance, research investigating the effects of glucose on memory for emotional material has produced mixed findings. Whereas some research has shown that glucose impairs memory for emotional material, other research has shown that glucose has no effect on emotional items. The aim of the present research was therefore to provide further investigation of the role of glucose on the recognition of words with emotional valence by exploring effects of dose and dual-task performance, both of which affect glucose facilitation effects. The results replicated past research in showing that glucose administration, regardless of dose or dual-task conditions, did not affect the memorial advantage enjoyed by emotional material. This therefore suggests an independent relationship between blood glucose levels and memory for emotional material.

Intention to learn influences the word frequency effect in recall but not in recognition memory.

Watkins, LeCompte, and Kim (2000) suggested that the recall advantage for rare words in mixed lists is due to a compensatory study strategy that favors the rare words. They found the advantage was reversed when rare and common words were studied under incidental learning conditions. The present study investigated the possibility that the rare-word advantage in recognition memory is also the result of a compensatory study strategy. Experiment 1 replicated the findings of Watkins et al. that the rareword advantage in recall is eliminated under incidental learning conditions. In contrast, Experiment 2 showed that the rare-word advantage in recognition memory is maintained under both intentional and incidental learning conditions. Experiment 3 replicated the results of Experiments 1 and 2 using different stimuli and a different orienting task. Finally, Experiment 4 showed that the rare-word advantage in recognition is maintained with pure lists. These findings show that the rare-word advantage in recognition memory is not the result of a compensatory study strategy. Instead, rare words are encoded more distinctively than common words, irrespective of participants’ intention to remember them.

Differential facilitative effects of glucose administration on Stroop task conditions.

Previous research has demonstrated that glucose administration improves memory performance. These glucose facilitation effects have been most reliably demonstrated in medial temporal lobe tasks with the greatest effects found for cognitively demanding tasks. The aim of the proposed research was to first explore whether such effects might be demonstrated in a frontal lobe task. A second aim was to investigate whether any beneficial effects of glucose may arise more prominently under tasks of increasing cognitive demand. To achieve these aims, the Stroop Task was administered to participants and effects of a drink of glucose (25 g) were compared with an aspartame-sweetened control drink on performance in young adults. Results demonstrated that glucose ingestion significantly reduced RTs in the congruent and incongruent conditions. No effect on error rates was observed. Of most importance was the finding that this glucose facilitative effect was significantly greatest in the most cognitively demanding task, that is, the incongruent condition. The present results support the contention that the glucose facilitation effect is most robust under conditions of enhanced task difficulty and demonstrate that such benefits extend to frontal lobe function.

Frontal transcranial direct current stimulation (tDCS) abolishes list-method directed forgetting

It is a point of controversy as to whether directed forgetting effects are a result of active inhibition or a change of context initiated by the instruction to forget. In this study we test the causal role of active inhibition in directed forgetting. By applying cathodal transcranial direct current stimulation (tDCS) over the right prefrontal cortex we suppressed cortical activity commonly associated with inhibitory control. Participants who underwent real brain stimulation before completing the directed forgetting paradigm showed no directed forgetting effects. Conversely, those who underwent sham brain stimulation demonstrated classical directed forgetting effects. We argue that these findings suggest that inhibition is the primary mechanism that results in directed forgetting costs and benefits.

Interaction between mode of learning and subjective experience: Translation effects in long-term memory

It has been suggested that writing auditorily presented words at encoding involves distinctive translation processes between visual and auditory domains, leading to the formation of distinctive memory traces at retrieval. This translation effect leads to higher levels of recognition than the writing of visually presented words, a non-translation effect. The present research investigated whether writing and the other translation effect of vocalisation (vocalising visually presented words) would be present in tests of recall, recognition memory and whether these effects are based on the subjective experience of remembering or knowing. Experiment 1 found a translation effect in the auditory domain in recall, as the translation effect of writing yielded higher recall than both non-translation effects of vocalisation and silently hearing. Experiment 2 found a translation effect in the visual domain in recognition, as the translation effect of vocalisation yielded higher recognition than both non-translation effects of writing and silently reading. This translation effect was attributable to the subjective experience of remembering rather than knowing. The present research therefore demonstrates the beneficial effect of translation in both recall and recognition, with the effect of vocalisation in recognition being based on rich episodic remembering.

No evidence for age-related differences in item-method directed forgetting of emotional words

Research indicates that people can intentionally forget, but it is less clear how ageing and emotion interact with this ability. The present research investigated item-method directed forgetting of negative, neutral, and positive words in young (20–35 years), young-old (60–74 years), and old-old (75–89 years) adults. Although old-old adults showed overall reduced memory compared to young and young-old adults, all three age groups showed intentional forgetting. Moreover, intentional forgetting was not affected by the valence of the word in any of the three age groups. These findings suggest that younger and older adults can intentionally forget information that is neutral or emotional in nature. The present study’s results extend previous research by showing that this ability is preserved in very old age.

Effects of glucose administration on category exclusion recognition

Previous research has produced discrepant findings as to whether glucose administration effects lead to enhanced recollection or arise only under dual-task conditions. The aim of the present research was to address these issues by firstly employing an alternative cognitively demanding paradigm that has been linked to hippocampal function, i.e. the Process Dissociation Procedure (PDP). A second aim was to use this paradigm to explore whether glucose affects qualitative aspects of memory function. To achieve these aims, the PDP task was administered to participants who had either consumed a glucose (25 g) or aspartame-sweetened control drink. Results demonstrated glucose facilitation effects only under difficult task conditions and with no such effect emerging for the process of recollection. The present results support the contention that the beneficial effects of glucose arise under hippocampally driven, cognitively demanding task conditions, and that this effect enhances quantitative but not qualitative aspects of recognition memory.