John Brown

Memorability, word frequency and negative recognition

Brown (1976) has provided an analysis of the effect of the memorability of an item on the confidence with which it is accepted or rejected in a test of recognition or recall. When the subject has no clear recollection of the inclusion of an item in an input list, he is assumed to evaluate its memorability in the context of the experiment before he decides whether to accept or reject it. If the judged memorability is high, the absence of a clear recollection is stronger evidence against the item than if it is low. A specific prediction is that memorable distractors in a recognition test will be more confidently rejected than non-memorable ones. This prediction was tested and confirmed in three experiments in which recognition was tested by 4-category rating. Except in Experiment I, items memorable to individual subjects were identified by administering a questionnaire. For example, in Experiment III forenames of immediate family were assumed to have high memorability. This experiment also included word frequency as a variable. Low-frequency distractors were rejected significantly more firmly than high-frequency distractors: extraction of memorable names enhanced this effect. The relationship of memorability to word frequency is discussed.

A comparison between transient amnesias induced by two drugs (diazepam or lorazepam) and amnesia of organic origin

The transient amnesias produced by drugs may have much in common with the more permanent amnesias associated with organic brain damage. This possibility was investigated using two benzodiazepines, diazepam and lorazepam, with medical student volunteers. In Experiment 1, 27 subjects received a 2ml intravenous injection of either diazepam (7.5 mg) or of lorazepam (3.0 mg) or of normal saline. In Experiment 2, a further 13 subjects were given lorazepam (2.5 mg) or saline. A double blind procedure was used. Neither drug had an appreciable effect on span-type short-term memory (except with 2-channel presentation). Both drugs produced severe anterograde amnesia in other forms of memory test: the amnesic effect of lorazepam lasted for several hours. This amnesia was not attributable to failures of perception. Lorazepam appeared to affect recognition even more than recall. In a test with lorazepam no evidence was obtained that the drug increases susceptibility to proactive interference. With both drugs, recall and recognition were unimpaired of material presented about 10 min before the injection; this shows that the drugs did not affect retrieval mechanisms.

Objective and subjective memory impairment in pregnancy

Pregnant subjects rated their memories as worse than normal and their ratings differed significantly from controls. Explicit memory tested by both recognition and recall was unimpaired. In contrast, implicit memory was significantly impaired in primigravidae. Impairment in implicit memory correlated with the subjective memory ratings. The dissociation of explicit and implicit memory is discussed.

Absence of priming coupled with substantially preserved recognition in lorazepam-induced amnesia

Two experiments are reported on priming when subjects are in an amnesic state induced by lorazepam. The primed tasks were completion of word-stems and generation of words from specified categories. In both experiments, lorazepam subjects showed no evidence of priming, whereas control subjects showed substantial priming. Recognition by the amnesic subjects of items produced in the priming tests, although impaired, was well above the chance level. These findings contrast with those obtained with organic amnesic subjects, for whom priming is typically normal but recognition is grossly impaired. The theoretical implications of this double dissociation between priming and recognition are discussed.

The effects of repeating a recognition test in lorazepam-induced amnesia: Evidence for impaired contextual memory as a cause of amnesia

In two experiments, a recognition test for an earlier presented list was given twice in immediate succession (Test 1 and Test 2). On the hypothesis that anterograde amnesia for episodic memory involves a deficit in contextual memory, amnesic subjects should confuse familiarity with distractor items gained during Test 1 with familiarity gained during original list presentation. As a result, they should think that they recognize more items on Test 2. This will lower recognition efficiency in Test 2 by increasing false alarms rather than by reducing hits. For subjects with an amnesia induced by lorazepam, but not for control subjects, recognition efficiency was substantially reduced in Test 2 in both experiments. As predicted, this impairment was due to a large increase in false alarms, with no decrease in the number of hits. The impairment could not be explained by a difference in recognition level between lorazepam and control subjects on Test 1. These findings therefore support the contextual memory deficit hypothesis of anterograde amnesia. Their implications for understanding the relationship between recall and recognition in amnesia are discussed.

Spatial and biological characterisation of the complete quinic acid utilisation gene cluster in Aspergillus nidulans

SummaryHeterologous probing of restriction digests of chromosomal DNA from Aspergillus nidulans with radioactively labelled probes encoding dehydroshikimate dehydratase (QA-4) and a repressor gene (QAI-S) from Neurospora crassa revealed a pattern of hybridisation inconsistent with an equivalent single copy of each gene in A. nidulans. Screening of size-selected and total genome A. nidulans DNA libraries allowed the isolation of four unique classes of sequence, two of which hybridised to the QA-4 probe, and two of which hybridised to the QA1-S probe. In each case, one of each pair of unique sequences was able to complement the equivalent mutations qutC (=QA-4) and qutR (=QA1-S) in A. nidulans, whereas the second of each pair was unable to complement the same mutation. The complementing sequences were physically mapped relative to the previously cloned A. nidulans QUT gene cluster, demonstrating that QUTR is distal and divergently transcribed from QUTA with approximately 3.6 kb between the ATG translational start codons, and that QUTC is transcribed in the same direction as QUTD on the other side of the cluster, approximately 1.65 kb downstream of the QUTD TAA translational stop signal. The physical and genetic maps of the QUT gene cluster correlate precisely. The non-complementing A. nidulans DNA sequences that hybridise to the N. crassa QA-4 (=QUTC) and QA1-S (=QUTR) fulfill many of the criteria characteristic of pseudogenes. The derived protein sequence of the QUTG gene shows a striking similarity to the protein sequence of bovine myo-inositol monophosphatase, indicating that they evolved from a common ancestor, and suggests a role for the QUTG gene, for which no function has previously been discovered, in expression of the QUT gene cluster.

Amnesic effects of intravenous diazepam and lorazepam

The amnesic effects of 2 benzodiazepine drugs, diazepam (Valium) and lorazepam (Ativan), have been investigated. Some of the effects were similar to those of certain clinical amnesic syndromes. The effects were more extensive than previous work has indicated.

Similarity relations in recognition: A model to explain Tulving's data

Abstract Tulving tested memory for pictures by two-choice recognition tests. Recognition was higher but less confident when the target and distractor of a pair were highly similar than when they were dissimilar but the distractor was highly similar to an untested target. Tulving was able to partially explain these results by distinguishing two types of similarity, physical and ecphoric, and by postulating interactive processing of target and distractor. A model is described which explains the above results without assuming interactive processing. It also accounts for the results he obtained with other types of test pairs.

Recognition and the direction of attention

Abstract Four related experiments are described in which evidence was sought for the hypothesis that the mechanism of attention enables unwanted inputs to be attenuated. In exp. 1, two words were presented simultaneously, one to each ear, in uncorrelated noise. A recognition test was then administered and the S attempted to select the word which had been presented to a designated ear. Under a k condition, the ear was designated in advance and under and nk condition it was designated only in the test itself. It was argued that, if a filter mechanism can attenuate unwanted inputs and if noise with the input adversely affects buffer storage at a sensory level (cf. Brown , 1959), then recognition should be superior under the k condition. However no difference between the conditions was found. In exp. 2, omitting the word to the unwantyed ear had a highly favourable effect on recognition, thus showing that there was plenty of scope for attenuation of the unwanted input to improve performance in exp. 1. Exp. 3 repeated exp. 1 but with noise-free inputs. Exp. 4 was similar to exp. 1 except that, instead of using a visual signal to try to switch-in the appropriate ear under the k condition, an auditory signal was given to the ear concerned. Negative results were again obtained. Various explanations for this failure to find evidence for the attenuation hypothesis are briefly discussed. One is consistent with a subsidiary finding that words were not tagged effectively by ear-of-arrival and a further experiment to test this hypothesis is suggested.