A design for an inexpensive and reliable olfactometer is presented. The design has several advantages for fMRI and electrophysiology investigators. These advantages include relatively rapid odorant rise times, computer control, multiple odor administration, and no ferrous materials near the subjects. In addition, the device is contamination resistant, and, because the air is neither warmed nor humidified, it is unlikely to become an incubator for bacteria. The olfactometer is constructed of off-the-shelf chromatography parts that require little modification.A variety of instruments have been developed over the past 100 years for the accurate and metered presentation of odors (for a review, see Prah, Sears, & Walker, 1995). Most of these instruments have been developed to meet the demands ofparticular situations or unique experimental settings, with each new need generating changes to existing devices. For instance, Kobal and Hummel (1988) developed an olfactometer with very rapid rise times in order to produce chemosensory event-related potentials. Laing (1986) also produced a unique olfactometer, for behavioral work with odor mixtures, that allowed odors to be introduced in very rapid succession. The advent of fMRI studies of olfactory and chemosensory processes presents a new set of needs, and the olfactometer described here has been developed to meet these needs in a simple and cost-effective manner.The fMRI laboratory presents several important and new demands on an olfactometer. The most obvious and essential is the absence of ferrous metal near the magnet. Ideally, the instrument should have the following features: (1) computer control; (2) effective delivery ofa variety ofodors, in series or randomly; (3) production ofan odor stimulus ofselectable and reliable duration in a constant airstream, without any additional type of ancillary stimulation (e.g., tactile, auditory); (4) resistance to contamination; (5) durability; (6) ease of operation, refilling, and cleaning; and (7) low cost. The olfactometer described here meets these needs and is relatively easy to construct. With the exception ofexcluding ferrous metals,

Four experiments used a running paired-associate task to investigate the effects of cueing 5s to forget items presented prior to a critical pair and to determine how 5s forget irrelevant information. Cueing 5s to forget prior information was effective when the list presentation times were equivalent for cued and noncuccl 5s. The Ss cued to forget prior items were less likely to use those items as response intrusions than were 5s who were not cued to forget the same items. In a postlist recognition task, cued and noncucd 5s recognized the to-be-forgotten items with equal facility.Turvey & Witt-Weiner & Reed, When we carry on conversations, perform intricate mathematical operations, and solve complex problems, we. demonstrate the remarkable facility that humans possess for holding, utilizing, and ignoring information over short intervals of time. Nearly all short-term memory studies have locussed on the determinants of storage and retrieval while only a very small number of experiments have been concerned with the factors involved in ignoring or setting aside information that is no longer relevant (

In Experiments 1 and 2, after studying a list containing connotatively neutral words that were presented once or were presented at various spacing intervals, subjects either attempted free recall or made affective judgments of the study-list targets along a pleasant/unpleasant dimension. Spacing effects occurred in recall, and massed items were judged to be more unpleasant than once-presented and spaced words. In the third experiment, subjects studied homogeneous lists composed of either connotatively good words or connotatively bad ones. Spacing effects were absent in the recall of both types of words because massed-practice words were recalled at a high level, one that was about the same as that for spaced-practice words. Affective judgments were unrelated to presentation condition, and both good and bad massed words were judged to be positive in affect. Although the data suggest that different study conditions can lead to different affective reactions, the results are moot with regard to the relationship between affect and the magnitude of spacing effects.Long-term recall of repeated verbal items increases as the temporal spacing between presentations increases. Theoretical accounts of this pervasive spacing effect (for reviews, see Glenberg, 1979;Hintzman, 1974;Melton, 1970) have focused on various cognitive activities such as encoding, storage, and retrieval. According to these theoretical efforts, processes underlying the spacing effect result from what social psychologists (e.g., Zajonc, 1980) call "cold cognitions." Cold cognitions represent analytic activities and their outcomes, such as feature analysis, rehearsal, and other typical mnemonic activities and internal representations. The general picture derived from research on the spacing effect seems to be that some sort of trace elaboration process and inattention to the second presentation of a massed item are among the most important factors leading to spacing effects (Crowder, 1976;Hintzman, 1976). Exactly why cold cognitions lead to trace multiplexing and failures to attend to massed repetitions has not been well specified. One reason for the failure to determine the causes of the spacing effect may be due to the fact that theories and research have tended to ignore "hot cognitions," which in contrast to cold cognitions include those associated with the affective domain of experience. Boredom, preference, positive arousal, and other affective states and processes have not received much emphasis as factors determining the spacing effect. The present paper reports several experiments designed to test the idea that affective processes play an important role in the spacing effect.

No abstract

The importance of retroactive interference (RI) in memory for spatial locations was studied by using a 12-arm radial maze and a standard RI paradigm. Animals in the RI condition first learned to choose 4 of the 12 arms, followed by training to a second set of 4 arms. In the control condition for interference, rats learned the first set of arms but were not trained to approach the second set. Thereafter, animals in each interference condition were assigned to groups (hippocampal, cortical control, unoperated control), the operations were carried out, and then all animals were tested for retention of the set of arms learned first. Contrary to predictions of the cognitive map theory, O' Keefe & Nadel, 1978), RI was found in control animals. The severe memory deficit found in hippocampals was not influenced by the interference variable. In addition to impaired performance early in relearning, rats with hippocampal lesions continued to make many errors throughout the 10 wk of testing, including choices to unbaited arms and repeated entries into baited arms. However, hippocampals eventually learned not to reenter unbaited arms. These data indicate a deficit in the selection and utilization of sets of responses and are interpreted as implicating the hippocampus in retrieval processes.