Retrieval of item frequency information in a continuous memory task

The accuracy and response latency of absolute frequency judgments were measured as a function of test lag (the number of intervening items between presentations of a test item) in a continuous memory task. Frequency was varied from one to three presentations in Experiments 1 and 2 and from one to five presentations in Experiment 3. The proportion of correct responses decreased as frequency increased, and correct mean response time tended to increase with frequency. Both accuracy and correct mean response time were found to be largely a function of the most recent test lag. The lag-latency functions were best described by piecewise linear functions, with the breakpoint occurring between lags 1 and 2. Continuous frequency estimation was also shown to improve with extended practice. The implications of the results are discussed with reference to trace strength, numerical-inference, and multiple-trace theories of frequency discrimination.     

The revelation effect for item and associative recognition: Familiarity versus recollection

The revelation effect occurs when items on a recognition test are more likely to be judged as being old if they are preceded by a cognitive task that involves the processing of similar types of stimuli. This effect was examined for item (single-word) and associative (word-pair) recognition. We found, in Experiments 1 and 2, a revelation effect for item, but not for associative recognition under normal study conditions. A revelation effect for both item and associative recognition was observed in Experiments 3 and 4 when study time was extremely brief, thus limiting the encoding of information that would support recall or recollection. In Experiment 5, we demonstrated that the revelation effect for item recognition is eliminated when item recognition decisions are made in the context of a study item. The results show that the revelation task influenced recognition decisions based on familiarity, but not decisions that involved recall or recollection.     

Shades of the mirror effect: Recognition of faces with and without sunglasses

A mirror effect was found for a stimulus manipulation introduced at test. When subjects studied a set of normal faces and then were tested with new and old faces that were normal or wearing sunglasses, the hit rate was higher and the false alarm rate was lower for normal faces. Hit rate differences were reflected in remember and sure recognition responses, whereas differences in false alarm rates were largely seen in know and unsure judgments. In contrast, when subjects studied faces wearing sunglasses, the hit rate was greater for test faces with sunglasses than for normal faces, but there was no difference in false alarm rates. These findings are problematic for single-factor theories of the mirror effect, but can be accommodated within a two-factor account.     

Irrelevant sensory stimuli interfere with working memory storage: Evidence from a computational model of prefrontal neurons

The encoding of irrelevant stimuli into the memory store has previously been suggested as a mechanism of interference in working memory (e.g., Lange & Oberauer, Memory, 13, 333–339, 2005; Nairne, Memory & Cognition, 18, 251–269, 1990). Recently, Bancroft and Servos (Experimental Brain Research, 208, 529–532, 2011) used a tactile working memory task to provide experimental evidence that irrelevant stimuli were, in fact, encoded into working memory. In the present study, we replicated Bancroft and Servos’s experimental findings using a biologically based computational model of prefrontal neurons, providing a neurocomputational model of overwriting in working memory. Furthermore, our modeling results show that inhibition acts to protect the contents of working memory, and they suggest a need for further experimental research into the capacity of vibrotactile working memory.     

Standing's power function in long-term memory

Summary Standing (1973) and Murray (1975) have both found that the number of items retrieved from long-term memory is a power function of the number of items presented. The present research reports three further experiments designed to validate this power function: the law was found to be upheld in paired associates recognition (for four levels of meaningfulness); for free recall (with or without retrieval cues at presentation and/or recall); and for incidental and intentional free recall and recognition. Some data of Roberts (1972) were also found to be fitted by a power function. The discussion deals with power functions as compared with linear functions and also with the relationships between slopes and intercepts of power functions.This research was supported by National Research Council of Canada Grant AO-126 to D.J. Murray. W.E. Hockley served as research assistant for Experiments 1 and 2; Experiment 3 was an Honours Thesis project carried out by Carol Pye.     

Interrupting recognition memory: Tests of a criterion-change account of the revelation effect

The revelation effect is evidenced by an increase in positive recognition responses when the test probe is immediately preceded by an unrelated problem-solving task. As an alternative to familiarity-based explanations of this effect (Hicks & Marsh, 1998; Westerman & Greene, 1998), Niewiadomski and Hockley (2001) proposed a decision-based account in which it is assumed that the problem-solving task displaces the study list context in working memory, leading subjects to adopt a more liberal recognition criterion. In the present study, we show that the revelation effect is seen when the stimulus materials are pure lists of very rare words or nonwords. In contrast, for mixed lists of common words and very rare words or nonwords, the revelation effect is found for common words but disappears for very rare words and nonwords. We argue that, in mixed lists, the liberal decision bias following the revelation task and the criterion changes between common words and very rare words and nonwords serve to offset each other.     

A test of two different revelation effects using forced-choice recognition

The revelation effect refers to the finding of an increased propensity to classify recognition test probes as old when they are preceded by a problem solving task. Recent research indicates that revelation effects are dissociable based on whether the revelation task involves an item that is the same as or different than the subsequently presented recognition probe. Using a two-alternative forced-choice design, we found a revelation effect for both words (Experiment 1) and nonwords (Experiment 2) in the condition where the revealed item was the same as the target item (same revelation condition), but no effect when the revealed item was different than either test alternative (different revelation condition). These results were replicated using a mixed list design containing both words and nonwords (Experiment 3). Results support Verde and Rotello’s (2004) two-factor account of the revelation effect, which proposes that changes in memory sensitivity underlie revelation effects in the same revelation condition, and that changes in the decision criterion are responsible in the different revelation condition.     

The effects of context in item-based directed forgetting: Evidence for “one-shot” context storage

The effects of context on item-based directed forgetting were assessed. Study words were presented against different background pictures and were followed by a cue to remember (R) or forget (F) the target item. The effects of incidental and intentional encoding of context on recognition of the study words were examined in Experiments 1 and 2. Recognition memory for the picture contexts was assessed in Experiments 3a and 3b. Recognition was greater for R-cued compared to F-cued targets, demonstrating an effect of directed forgetting. In contrast, no directed forgetting effect was seen for the background pictures. An effect of context-dependent recognition was seen in Experiments 1 and 2, such that the hit rate and the false-alarm rate were greater for items tested in an old compared to a novel context. An effect of context-dependent discrimination was also observed in Experiment 2 as the hit rate was greater for targets shown in their same old study context compared to a different old context. The effects of context and directed forgetting did not interact. The results are consistent with Malmberg and Shiffrin’s (Journal of Experimental Psychology: Learning, Memory, and Cognition, 31, 322–336, 2005) “one-shot” context storage hypothesis that assumes that a fixed amount of context is stored in the first 1 to 2 s of the presentation of the study item. The effects of context are independent of item-based directed forgetting because context is encoded prior to the R or F cue, and the differential processing of target information that gives rise to the directed forgetting effect occurs after the cue.