视觉长时记忆激活度对促进视觉短时记忆的影响

短时记忆与长时记忆的关系是记忆领域研究的重要内容。基于此, 研究者们就视觉长时记忆是否能促进视觉短时记忆的问题展开了大量研究, 但所得出的结论并不一致。通过不同程度的学习形成不同激活度的视觉长时记忆, 考察对几何图形的视觉长时记忆是否能对变化检测中的短时记忆起到促进作用。结果发现, 低激活水平的视觉长时记忆不能促进视觉短时记忆, 而事先存在且高度激活的视觉长时记忆对视觉短时记忆却具有促进作用; 同时, 随着视觉长时记忆激活水平的提高, 刺激间间隔的效应值也逐渐减小。本研究说明, 视觉长时记忆能否促进视觉短时记忆取决于视觉长时记忆的激活水平, 高激活的视觉长时记忆对阻止视觉短时记忆痕迹的迅速消退具有重要意义。     

Inferred threat and safety: Symbolic generalization of human avoidance learning

Symbolic generalization of avoidance may underlie the aetiology and maintenance of anxiety disorders. The aim of the present study was to demonstrate inferred threat-avoidance and safety (non-avoidance) behaviours that occur in the presence of stimuli indirectly related to learned threat and safety cues. A laboratory experiment was conducted involving two symbolic stimulus equivalence relations consisting of three physically dissimilar stimuli (avoidance cues: AV1–AV2–AV3 and neutral cues: N1–N2–N3). During avoidance learning involving aversive images and sounds, a key-press avoidance response was trained for one member of one of the relations (AV2) and non-avoidance for another (N2). Inferred threat and safety behaviour and ratings of the likelihood of aversive events were tested with presentations of all remaining stimuli. Findings showed a significantly high percentage of avoidance to both the learned and inferred threat cues and less avoidance to both the learned and inferred safety cues. Ratings in the absence of avoidance were high during training and testing to threat cues and low to safety cues and were generally lower in the presence of avoidance. Implications for associative and behavioural accounts of avoidance, and modern therapies for anxiety disorders are discussed.     

Estimating the growth of internal evidence guiding perceptual decisions

Perceptual decision-making is thought to involve a gradual accrual of noisy evidence. Temporal integration of the evidence reduces the relative contribution of dynamic internal noise to the decision variable, thereby boosting its signal-to-noise ratio. We aimed to estimate the internal evidence guiding perceptual decisions over time, using a novel combination of external noise and the response signal methods. Observers performed orientation discrimination of patterns presented in external noise. We varied the contrast of the patterns and the delay at which observers were forced to signal their decision. Each test stimulus (patterns and noise sample) was presented twice. Across two experiments we varied the availability of the visual stimulus for processing. Observer model analyses of discrimination accuracy and response consistency to two passes of the same stimulus, suggested that there was very little growth in the internal evidence. The improvement in accuracy over time characterised by the speed-accuracy trade-off function predominantly reflected a decreasing proportion of non-visual decisions, or pure guesses. There was no advantage to having the visual patterns visible for longer than 80 ms, indicating that only the visual information in a short window after display onset was used to drive the decisions. The remarkable constancy of the internal evidence over time suggests that temporal integration of the sensory information was very limited. Alternatively, more extended integration of the evidence from memory could have taken place, provided that the dominant source of internal noise limiting performance occurs between-trials, which cannot be reduced by prolonged evidence integration.     

Evaluating models of recognition memory using first- and second-choice responses

Swets, Tanner Jr., and Birdsall (1961) proposed a 4-alternative forced-choice task with two choices (4AFC-2R) for distinguishing between the Equal-Variance Signal Detection model and the One-High Threshold model. This task was recently implemented in the field of recognition memory (Parks & Yonelinas, 2009), a field in which several candidate models have been proposed. One advantage of the 4AFC-2R task is that it permits parameter estimation and goodness of fit testing, something which so far was only possible through the use of Receiver Operating Characteristic (ROC) functions for the more complex candidate models. The present article provides a thorough characterization and comparison of the main recognition memory models in the context of this task. Results are illustrated by a reanalysis of Parks and Yonelinas’ original data, revealing a preference for hybrid approaches to recognition memory, more specifically for the dual-process model (Yonelinas, 1997), whereas pure signal detection models performed poorly. The present analysis provides an assessment of the merits and limitations of this task, highlighting future research applications.     

Behavior-Based Assessment of the Auditory Abilities of Brushtail Possums

Brushtail possums (Trichosurus vulpecula) were trained to press a right lever when a tone was presented (a tone‐on trial) and a left lever when a tone was not presented (a tone‐off trial) to gain access to food. During training the tone was set at 80 dB(A), with a frequency of 0.88 kH for 3 possums and of 4 kH for the other 2. Once accuracy was over 90% correct across five consecutive sessions, a test session was conducted where the intensity of the tone was reduced by 8 dB(A) over blocks of 20 trials until accuracy over a block fell below 60%. After each test session, training sessions were reintroduced and continued until accuracy was again over 90%, when another test session was conducted. This process continued until there were at least five test sessions at that tone frequency. The same procedure was then used with frequencies of 0.20, 0.88, 2, 4, 10, 12.5, 15, 20, 30, and 35 kHz. Percentage correct and d' decreased approximately linearly for all possums as tone intensity reduced. Both sets of lines were shallowest at the higher frequencies and steepest at the lower frequencies. Hit and false alarm rates mirrored each other at high frequencies but were asymmetric at lower frequencies. Equal d' contours showed that sensitivity increased from 2 to 15 kHz and continued to be high over 20 to 35 kHz. The possums remained sensitive to the 20 to 35 kHz tones even at low intensities. The present study is the first to report the abilities of possum to detect tones over this range of frequencies and its results support the findings of a microelectrode mapping survey of possums' auditory cortex.     

Evidence of differential performance on simultaneous and sequential lineups for individuals with autism-spectrum traits

Given the impaired facial recognition of autistic individuals, we examined whether certain autism-spectrum traits affected eyewitness identification performance in a general adult population. In a sample of 120 individuals, levels of autism-spectrum traits were examined in relation to performance on simultaneous vs. sequential lineups using a signal detection paradigm. For simultaneous lineups, total Autism Spectrum Quotient (AQ) scores and scores on the excessive Attention to detail subscale were related to fewer hits and a more conservative response criterion. Attention to detail interacted with lineup type in that it was significantly related to improved discrimination accuracy and a less conservative response criterion in sequential lineups, but with impaired discrimination accuracy and a more conservative response criterion in simultaneous lineups. Higher AQ scores on the Attention switching subscale resulted in fewer hits, lower discrimination accuracy, and a more conservative response criterion with sequential lineups. Additionally, partial disguises led to more false alarms but not decreased accuracy. More thorough investigations of the effect of lineup type on identifications are needed before policy changes are recommended.     

The right hemisphere advantage in visual change detection depends on temporal factors

What accounts for the Right Hemisphere (RH) functional superiority in visual change detection? An original task which combines one-shot and divided visual field paradigms allowed us to direct change information initially to the RH or the Left Hemisphere (LH) by deleting, respectively, an object included in the left or right half of a scene presented centrally. We manipulated the perceptual salience and semantic relevance of the change as well as the duration of the Inter-Stimulus Interval (ISI) between the scenes in order to clarify the role of the RH in memory and attention processes, and to explore whether lengthening the ISI would enhance the contribution of the LH. When analyzing data collapsed over the two levels (high vs. low) of salience and of relevance, changes were better detected in the left visual field (lvf) than in the right visual field (rvf) in the case of a short ISI, while no difference emerged in the case of a long ISI. Moreover, lengthening the ISI resulted in a performance decrement in the lvf, both for accuracy and response speed. The fact that the RH superiority was limited to short intervals indicates that stimulus-driven orienting contributes more than perceptual processing to this hemispheric asymmetry. When considering perceptual and semantic properties of the change, the effect of the ISI duration seemed to specifically emerge in the case of low relevance, with an enhancement of accuracy in the rvf when comparing the long with the short ISI. This suggests that the ISI influence on hemispheric performance operates on different levels.     

The effects of emotion priming on visual search in socially anxious adults

This study examined the effects of emotion priming on visual search in participants characterised for different levels of social anxiety. Participants were primed with five facial emotions (angry, fear, happy, neutral, and surprised) and one scrambled face immediately prior to visual search trials involving finding a slanted coloured line amongst distractors, as reaction times and accuracy to target detection were recorded. Results suggest that for individuals low in social anxiety, being primed with an angry, surprised, or fearful face facilitated visual search compared to being primed with scrambled, neutral or happy faces. However, these same emotions degraded visual search in participants with high levels of social anxiety. This study expands on previous research on the impact of emotion on attention, finding that amongst socially anxious individuals, the effects of priming with threat extend beyond initial attention capture or disengagement, degrading later visual search.     

People look at the object they fear: oculomotor capture by stimuli that signal threat

It is known that people covertly attend to threatening stimuli even when it is not beneficial for the task. In the current study we examined whether overt selection is affected by the presence of an object that signals threat. We demonstrate that stimuli that signal the possibility of receiving an electric shock capture the eyes more often than stimuli signalling no shock. Capture occurred even though the threat-signalling stimulus was neither physically salient nor task relevant at any point during the experiment. Crucially, even though fixating the threat-related stimulus made it more likely to receive a shock, results indicate that participants could not help but doing it. Our findings indicate that the presence of a stimulus merely signalling the possibility of receiving a shock is prioritised in selection, and exogenously captures the eyes even when this ultimately results in the execution of the threat (i.e. receiving a shock). Oculomotor capture was particularly pronounced for the fastest saccades which is consistent with the idea that threat influences visual selection at an early stage of processing, when selection is mainly involuntarily.