Corbin Cunningham

Taming the White Bear Initial Costs and Eventual Benefits of Distractor Inhibition

Previous research indicates that prior information about a target feature, such as its color, can speed search. Can search also be speeded by knowing what a target will not look like? In the two experiments reported here, participants searched for target letters. Prior to viewing search displays, participants were prompted either with the color in which one or more nontarget letters would appear (ignore trials) or with no information about the search display (neutral trials). Critically, when participants were given one consistent color to ignore for the duration of the experiment, compared with when they were given no information, there was a cost in reaction time (RT) early in the experiment. However, after extended practice, RTs on ignore trials were significantly faster than RTs on neutral trials, which provides a novel demonstration that knowledge about nontargets can improve search performance for targets. When the to-be-ignored color changed from trial to trial, no RT benefit was observed.

Massive memory revisited: Limitations on storage capacity for object details in visual long-term memory

Previous work suggests that visual long-term memory (VLTM) is highly detailed and has a massive capacity. However, memory performance is subject to the effects of the type of testing procedure used. The current study examines detail memory performance by probing the same memories within the same subjects, but using divergent probing methods. The results reveal that while VLTM representations are typically sufficient to support performance when the procedure probes gist-based information, they are not sufficient in circumstances when the procedure requires more detail. We show that VLTM capacity, albeit large, is heavily reliant on gist as well as detail. Thus, the nature of the mnemonic representations stored in VLTM is important in understanding its capacity limitations.

Lions or tigers or bears: Oh my! Hybrid visual and memory search for categorical targets

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The capture of attention by entirely irrelevant pictures of calorie-dense foods

Inborn preference for palatable energy-dense food is thought to be an evolutionary adaptation. One way this preference manifests itself is through the control of visual attention. In the present study, we investigated how attentional capture is influenced by changes in naturally occurring goal-states, in this case desire for energy-dense foods (typically high fat and/or high sugar). We demonstrate that even when distractors are entirely irrelevant, participants were significantly more distracted by energy-dense foods compared with non-food objects and even low-energy foods. Additionally, we show the lability of these goal-states by having a separate set of participants consume a small amount of calorie-dense food prior to the task. The amount of distraction by the energy-dense food images in this case was significantly reduced and no different than distraction by images of low-energy foods and images of non-food objects. While naturally occurring goal-states can be difficult to ignore, they also are highly flexible.

Analog Computer-Aided Detection (CAD) information can be more effective than binary marks

In socially important visual search tasks, such as baggage screening and diagnostic radiology, experts miss more targets than is desirable. Computer-aided detection (CAD) programs have been developed specifically to improve performance in these professional search tasks. For example, in breast cancer screening, many CAD systems are capable of detecting approximately 90% of breast cancer, with approximately 0.5 false-positive detections per image. Nevertheless, benefits of CAD in clinical settings tend to be small (Birdwell, 2009) or even absent (Meziane et al., 2011; Philpotts, 2009). The marks made by a CAD system can be “binary,” giving the same signal to any location where the signal is above some threshold. Alternatively, a CAD system presents an analog signal that reflects strength of the signal at a location. In the experiments reported, we compare analog and binary CAD presentations using nonexpert observers and artificial stimuli defined by two noisy signals: a visible color signal and an “invisible” signal that informed our simulated CAD system. We found that analog CAD generally yielded better overall performance than binary CAD. The analog benefit is similar at high and low target prevalence. Our data suggest that the form of the CAD signal can directly influence performance. Analog CAD may allow the computer to be more helpful to the searcher.

Visual Long-term Memory Can Replace Active Maintenance in Visual Working Memory

Humans have remarkable visual long-term memory abilities, capable of storing thousands of objects with significant detail. However, it remains unknown how such memory is utilized during the short-term maintenance of information. Specifically, if people have a previously encoded memory for an item, how does this affect subsequent working memory for that same item? Here, we demonstrate people can quickly and accurately make use of visual long-term memories and therefore maintain less perceptual information actively in working memory. We assessed how much perceptual information is actively maintained in working memory by measuring neural activity during the delay period of a working memory task using electroencephalography. We find that despite maintaining less perceptual information in working memory when long-term memory representations are available, there is no decrement in memory performance. This suggests under certain circumstances people can dynamically disengage working memory maintenance and instead use long-term memories when available. However, this does not mean participants always utilize long-term memory. In a follow-up experiment, we introduced additional perceptual interference into working memory and found participants actively maintained items in working memory even when they had existing long-term memories available. These results clarify the kinds of conditions under which long-term and working memory operate. Specifically, working memory is engaged when new information is encountered or perceptual interference is high. Visual long-term memory may otherwise be rapidly accessed and utilized in lieu of active perceptual maintenance. These data demonstrate the interactions between working memory and long-term memory are more dynamic and fluid than previously thought.

Simulating the Fidelity of Data for Large Stimulus Set Sizes and Variable Dimension Estimation in Multidimensional Scaling

Multidimensional scaling (MDS) is a statistical technique commonly used to model the psychological similarity among sets of stimulus items. Typically, MDS has been used with relatively small stimulus sets (30 items or fewer), in part due to the laborious nature of computational analysis and data collection. Modern computing power and newly advanced techniques for speeding data collection have made it possible to conduct MDS with many more stimuli. However, it is as yet unclear if MDS is as well-equipped to model the similarity of large stimulus sets as it is for more modest ones. Here, we conducted 337,500 simulation experiments, wherein hypothetical “true” MDS spaces were created, along with error-perturbed data from simulated “participants.” We examined the fidelity with which the spaces resulting from our “participants” captured the organization of the “true” spaces, as a function of item set size, amount of error in the data (i.e., noise), and dimensionality estimation. We found that although higher set sizes decrease model fit (i.e., they produce increased “stress”), they largely tended to increase determinacy of MDS spaces. These results are predicated, however, on the appropriate estimation of dimensionality of the MDS space. We argue that it is not only reasonable to adopt large stimulus set sizes but tends to be advantageous to do so. Applying MDS to larger sets is appealing, as it affords researchers greater flexibility in stimulus selection, more opportunity for exploration of their stimuli, and a higher likelihood that observed relationships are not due to stimulus-specific idiosyncrasies.

The lower bounds of massive memory: Investigating memory for object details after incidental encoding

Visual long-term memory capacity appears massive and detailed when probed explicitly. In the real world, however, memories are usually built from chance encounters. Therefore, we investigated the capacity and detail of incidental memory in a novel encoding task, instructing participants to detect visually distorted objects among intact objects. In a subsequent surprise recognition memory test, lures of a novel category, another exemplar, the same object in a different state, or exactly the same object were presented. Lure recognition performance was above chance, suggesting that incidental encoding resulted in reliable memory formation. Critically, performance for state lures was worse than for exemplars, which was driven by a greater similarity of state as opposed to exemplar foils to the original objects. Our results indicate that incidentally generated visual long-term memory representations of isolated objects are more limited in detail than recently suggested.