Modeling experimentally induced strategy shifts

In dynamic decision-making environments, observers must continuously adjust their decision-making strategies. Previous research has focused on internal fluctuations in decision mechanisms, without regard to how these changes are induced by environmental changes. We developed a simple paradigm in which we manipulated task difficulty, thereby inducing changes in decision processes. We applied this paradigm to recognition memory, manipulating task difficulty by changing the similarity of lures to targets. More difficult decision environments caused participants to make more careful decisions, but these changes did not appear immediately. We propose a simple theoretical account for these data, using a dynamic version of signal detection theory fitted to individual subjects. Our model represents a significant departure from existing models because it incorporates subject-controlled parameters that may adjust over time in response to environmental changes.     

Strength-based criterion shifts in recognition memory

In manipulations of stimulus strength between lists, a more lenient signal detection criterion is more frequently applied to a weak than to a strong stimulus class. However, with randomly intermixed weak and strong test probes, such acriterion shift often does not result. A procedure that has yieldeddelay-based within-list criterion shifts was applied to strength manipulations in recognition memory for categorized word lists. When participants made semantic ratings about each stimulus word, strength-based criterion shifts emerged regardless of whether words from pairs of categories were studied in separate blocks (Experiment 1) or in intermixed blocks (Experiment 2). In Experiment 3, the criterion shift persisted under the semantic-rating study task, but not under rote memorization. These findings suggest that continually adjusting the recognition decision criterion is cognitively feasible. They provide a technique for manipulating the criterion shift, and they identify competing theoretical accounts of these effects.     

Associative false recognition occurs without strategic criterion shifts

In the DRM (Deese/Roediger and McDermott) false memory paradigm, subjects studied lists of words associated with nonpresented critical words. They were tested in one of four instructional conditions. In a standard condition, subjects were not warned about the DRM Effect. In three other conditions, they were told to avoid false recognition of critical words. One group was warned before study of the lists (affecting encoding and retrieval processes), and two groups were warned after study (affecting only retrieval processes). Replicating prior work, the warning before study considerably reduced false recognition. The warning after study also reduced false recognition, but only when critical items had never been studied; when critical items were studied in half the lists so that subjects had to monitor memory for their presence or absence, the warning after study had little effect on false recognition. Because warned subjects were trying to avoid false recognition, the high levels of false recognition in the latter condition cannot be due to strategically guessing that critical test items were studied. False memories in the DRM paradigm are not caused by such liberal criterion shifts.     

The effects of experimentally induced stress on false recognition.

The fallibility of memory has become an issue of considerable practical and theoretical importance. Here we studied the impact of experimentally induced stress on the ability of human participants to accurately recognise words presented on a list. We found that stress selectively disrupted participants' ability to distinguish words that were presented for study from critical lure words that were semantically related, but not presented for study. This finding indicates that stress, possibly through its impact on the hippocampus and prefrontal cortex, can potentiate false memories.     

Intra- and interpersonal consequences of experimentally induced concealment

Secrecy, concealment, and thought suppression are assumed to be important aspects of psychopathology. However, most studies address these from an intrapersonal perspective. This study investigates both the intra- as well as the interpersonal consequences of experimentally induced concealment. Two experiments are described in which non-clinical participants were given a concealment instruction (i.e. avoid talking about a certain topic) in a conversation with an interviewer. In the neutral condition there was no such restraint. Interviewees were more tense and more aware during the concealment condition than during the neutral condition, whereas the interviewers were not aware of the participants' avoidance of the concealment topic. The second counterbalanced experiment replicated the results from the initial experiment. The hypotheses were supported that concealment can be induced experimentally leading to thought suppression and elevated levels of discomfort in the concealing individuals, without their conversation partners noticing. Implications for clinical practice are discussed.     

Effects of contextual questions on experimentally induced dysphoria

In a replication and extension of Watkins, Teasdale, and Williams (2003), a scrambled sentences paradigm was used to test whether prompting contextual processing of negative cognitive primes would limit the activation of dysphoric mood. Participants were divided into two groups and, after a dysphoric mood induction procedure, were asked to unscramble sentences that either did or did not emphasise the contextual aspects of moods. Consistent with Watkins et al., participants’ despondency decreased significantly more in the contextual group than in the neutral group. This effect could not be accounted for by variations in the way sentences were unscrambled.     

Enduring consequences of experimentally induced biases in interpretation

Previous research has demonstrated that it is possible to induce biases in the interpretation of ambiguous text passages by training. Participants consistently trained to interpret emotionally ambiguous passages in either a negative or positive direction show training-congruent effects when presented with new ambiguous material. These training effects are demonstrated by participants' subsequent recognition ratings for disambiguating sentences, which represent both possible meanings of the novel ambiguous test passages. In this series of experiments, we investigated the durability of these training effects over time spans of up to 1 day and found them to be robust. The findings encourage us to believe that induced biases may serve as a useful analogue to those observed clinically.     

Evidence for criterion shifts in visual perceptual learning: data and implications

Work on visual perceptual learning for contrast detection has shown that reliable decreases in detection thresholds are accompanied by reliable increases in false alarm rates (Wenger & Rasche, 2006). The present study assesses the robustness and replicability of these changes, demonstrating that they are independent of a variety of task demands (i.e., the specific method used for perceptual practice and threshold estimation) and the presence or absence of trial-by-trial feedback and that the source of the increases can be found in shifts in changes in sensitivity and in bias for detection, identification, or both. Although the increase in false alarm rates suggests a strategic shift in response criteria for detection, we demonstrate that there are multiple potential explanations, including explanations that do not require strategic shifts on the part of the observer. The empirical evidence and analysis of alternative explanations reinforce the inference that visual perceptual learning may involve more than changes in perceptual sensitivity and that cortical circuits beyond the primary visual areas may be involved.     

Brain activations associated with shifts in response criterion on a recognition test.

Sensitivity and bias can be manipulated independently on a recognition test. The goal of this fMRI study was to determine whether neural activations associated with manipulations of a decision criterion would be anatomically distinct from neural activations associated with manipulations of memory strength and episodic retrieval. The results indicated that activations associated with shifting criteria (a manipulation of bias) were located in bilateral regions of the lateral cerebellum, lateral parietal lobe, and the dorsolateral prefrontal cortex extending from the supplementary motor area. These regions were anatomically distinct from activations in the prefrontal cortex produced during memory-based retrieval processes (manipulations of sensitivity), which tended to be more medial and anterior. These later activations are consistent with previous studies of episodic retrieval. Determining patterns of neural activations associated with decision-making processes relative to memory processes has important implications for Cognitive Neuroscience, including the use of these patterns to compare memory models in different paradigms.