Effects of exact and category repetition in true and false recognition memory.

Two experiments used the distinction between remembering and knowing to investigate the effects of exact and category repetition in recognition memory. In Experiment 1, exact repetition enhanced remember responses but had no reliable effect on know responses. In Experiment 2, category repetition enhanced correct know responses but had no effect on correct remember responses. Category repetition also increased false positive remember and know responses. It is argued that exact repetition influences the recollection component of recognition memory via the creation of multiple episodic traces, each of which is potentially capable of supporting a remember response, whereas category repetition influences the familiarity component of recognition memory by enhancing the fluency with which test items are processed.

Cognitive effort and recollective experience in recognition memory.

The difficulty of the cognitive operations required to process study items was manipulated in two experiments investigating recollective experience. In subsequent recognition tests, subjects indicated whether their recognition judgements for items processed in these tasks were based on recollection ("remember" responses) or on familiarity ("know" responses). In Experiment 1 target items were presented in the context of a category decision task. It was found that remember responses increased with the difficulty of the category decision. For positive instances, remember responses were greater for items of low instance frequency than for items of high instance frequency, while for negative instances remember responses were greater for items from similar categories than for items from dissimilar categories. These effects were not present in know responses. In Experiment 2, remember responses were more frequent when study items had been presented in the form of anagrams to be solved than when they had been presented in the form of words to be read aloud. The incidence of know responses was not affected by the format in which study items were presented. Source judgements were also more accurate when recognition was based on recollection. It is argued that the type of conscious awareness experienced during recognition is determined by the knowledge activated by items presented in the recognition test, which in turn is determined by the nature of the operations engaged at encoding.

The representation of nonstructural information in visual memory: evidence from image combination.

Two experiments investigated the differential representation of the figure and ground of a picture in visual short-term and long-term memory. It is known (Hitch, Brandimonte, & Walker, 1995) that subjects find it more difficult to combine mental images of two separately presented pictures in order to identify a novel form when the two pictures are incongruent in color (i.e., when a black-on-white line drawing has to be combined with a white-on-black drawing). In the present experiments, the figures were depicted in solid form to allow color congruity to be varied independently for figure and ground. Results showed a clear impairment in image combination when the to-be-combined figures were incongruent in color (black-on-gray and white-on-gray) but not when their grounds were incongruently colored (gray-on-black and gray-on-white). In this way, image combination was seen to be supported by a representation of the object depicted in the picture rather than by a literal representation of the picture itself (i.e., a pictorial code). In line with previous findings, the same representation was seen to support image combination based on short-term memory (Experiment 1) and long-term memory (Experiment 2), provided that in the latter case verbal recoding was precluded. When verbal recoding was allowed, image combination based on long-term memory was insensitive to color congruity, implying the involvement of a more abstract structural representation.

Remembering, familiarity, and source monitoring.

Two experiments investigated recollective experience in a source monitoring task. Subjects saw an array of objects and performed, watched, or imagined actions involving pairs of objects. In a subsequent recognition test, subjects indicated whether their recognition judgements were made on the basis of conscious recollective experience ("remember" responses), or on some other basis such as familiarity ("know" responses). The proportions of correct "remember" responses for both objects and actions decreased from performed, through watched, to imagined actions, whereas the proportions of correct "know" responses were uninfluenced by the source of the memories. In addition, the relationship between recollective experience and accuracy of source judgement varied across sources. Source accuracy for performed actions was obtained only in "remember" responses, whereas source accuracy for performed actions was obtained only in "remember" responses, whereas source accuracy for imagined actions was obtained only in "know" responses. Source accuracy for watched actions was obtained in both "remember" and "know" responses. The findings suggest that the types of memory attributes available at retrieval determine the quality of subsequent memory experience, and it is proposed that memories with strongly self-referential attributes (arising from performed actions) powerfully cue recollective experience during retrieval.

Pictures, images, and recollective experience.

Five experiments investigated the influence of picture processing on recollective experience in recognition memory. Subjects studied items that differed in visual or imaginal detail, such as pictures versus words and high-imageability versus low-imageability words, and performed orienting tasks that directed processing either toward a stimulus as a word or toward a stimulus as a picture or image. Standard effects of imageability (e.g., the picture superiority effect and memory advantages following imagery) were obtained only in recognition judgments that featured recollective experience and were eliminated or reversed when recognition was not accompanied by recollective experience. It is proposed that conscious recollective experience in recognition memory is cued by attributes of retrieved memories such as sensory-perceptual attributes and records of cognitive operations performed at encoding.

A 5-bromodeoxyuridine-sensitive interval during drosophila myogenesis.

Drosophila myogenesis was monitored in vitro and the cells were treated with 5-bromodeoxyuridine (BrdU) or with thymidine at certain intervals. Muscle cells were scored for survival, contractility, and the uptake of thymidine and BrdU. Results indicated that the final S period for myoblasts takes place in vitro between 1.3 and 3.3 h following the initiation of gastrulation in the donor embryos. Treatment with 10(-4) M BrdU during this internal inhibited myogenesis, but later treatment did not. Thymidine reversed or prevented the BrdU effect if given before the final myoblast division, but not if given after wards. All results support the hypothesis that BrdU inhibits Drosophila myogenesis through its incorporation into DNA.