developingintelligence | January 14, 2009
Synaesthesia refers to the phenomenon where certain perceptual stimuli induce an unrelated and illusory perception - for example, a digit-color synaesthete may experience a sensation of the color green whenever exposed to the number 3. The relationships between the inducers and the induced synaesthetic experience are widely considered random; one anecodotal explanation is that letter-color synaesthesia could reflect a childhood memory of the particular colors used inrefrigerator magnet letters.
A recent Current Biology article from Kadosh, Henik and Walsh turns this common wisdom on its…
developingintelligence | January 12, 2009"Priming" refers to a pervasive phenomenon in which the repetition of a particular stimulus, response, or thought process facilitates its subsequent use. Might this phenomenon extend to more "executive" capacities as well?
In a recent article from theJournal of Experimental Psychology: Human Perception and Performance, Verbruggen, Logan, Liefooghe & Vandierendonck explore the phenomenon of repetition priming in the stop-signal paradigm. The stop signal paradigm requires subjects to make one or more "Go" responses to a particular stimulus class (typically, to press one button in response…
developingintelligence | January 9, 2009There's little evidence that "staging" the training of neural networks on language-like input - feeding them part of the problem space initially, and scaling that up as they learn - confers any consistent benefit in terms of their long term learning (as reviewed yesterday).
To summarize that post, early computational demonstrations of the importance of starting small were subsequently cast into doubt by numerous replication failures, with one exception: the importance of starting small is replicable when the training data lack temporal correlations. This leads to slow learning of the…
developingintelligence | January 8, 2009An early classic in computational neuroscience was a 1993 paper by Elman called "The Importance of Starting Small." The paper describes how initial limitations in a network's memory capacity could actually be beneficial to its learning of complex sentences, relative to networks that were "adult-like" from the start. This still seems like a beautiful idea - the cognitive limitations of children may somehow be adaptive for the learning they have yet to do.
And Elman is not alone in proposing it; a number of other researchers have proposed that a lack of cognitive control or working memory…
developingintelligence | January 7, 2009The ability to suppress unwanted thoughts and actions is thought (by some) to be crucial in your ability to control behavior. However, alternative perspectives suggest that this emphasis on suppression or "inhibition" is misplaced. These perspectives, largely motivated by computational models of the brain, suggest that alternative abilities (such as the activation or "active maintenance" of wanted thoughts and actions) are the real underlying mechanisms of inhibition and suppression.
This debate is given new life by the emerging science of "executive function training," which carefully…
developingintelligence | January 6, 2009For the basics about multivariate fMRI "mind-reading" techniques, see the video below. Some of it is based on this 2007 Haynes et al paper from Current Biology, described in more detail following the video.
What Haynes et al have done is to ask 8 subjects to freely decide either to add or subtract two numbers, and to select among 4 options an answer corresponding to the task they chose. After repeating this process many times, the authors ran a pattern classifier on the metabolic activity recorded in the brain.
This pattern classifier was run on the unsmoothed fMRI data - smoothing is…
developingintelligence | December 17, 2008New work by Minear & Shah shows that as little as 2 hours of practice can promote improvements in multitasking that generalize beyond the particular tasks trained. Specifically, they show that performance on individual tasks can be made more efficient while multitasking, but the efficiency of actually switching between them cannot. The data supporting this conclusion is fairly complex, but significantly adds to theoretical accounts to a number of previous studies showing that even the highest levels of cognitive processing (the so-called "executive functions") can be improved with…
developingintelligence | December 15, 2008When you need to stop yourself from committing some response, do you simply freeze - like a deer in the headlights - or can you selectively inhibit only the undesired action? The question is important because the ability to stop or inhibit a planned or prepotent action may be a central feature of so-called "executive functions," those capacities which are tightly related to fluid intelligence, academic success, and genetic factors. Yet surprisingly little is known about whether stopping can be global, selective, or both.
Some answers to this question come from selective stopping paradigms…
developingintelligence | October 3, 2008What if training ourselves on one task yielded improvements in all other tasks we perform? This is the promise of the cognitive training movement, which is increasingly showing that such "far transfer" of training is indeed possible, while short of being "universal transfer." Interestingly, this phenomenon might be most likely to occur for some of the most abstract and challenging cognitive functions.
New evidence for this claim comes from an in-press article at Psychological Science, by Persson & Reuter-Lorenz. The authors used several tasks which have been shown to engage the left…
developingintelligence | September 26, 2008My friend Geoff once said that "all cognition is social." Smugly, I reminded myself that the conclusions of cognitive psychologists are drawn on evidence where social cues are kept constant. But even in the absence of confounding social cues, perhaps the underlying cognitive processes themselves are caused by social factors.
A great example of this comes from today's issue of Science, in which Topal et al describe how a well known "cognitive" phenomenon - perseveration - may be dramatically influenced by social cues.
Topel et al focus on a situation in which very young infants will…
developingintelligence | September 12, 2008Much evidence supports the idea that parietal cortex is involved in the simple maintenance of information, such as in object permanence paradigms (also here) and other tasks. This evidence is part of the justification for the "parietofrontal integration theory", which suggests that parietal areas work in concert with prefrontal regions of the brain to accomplish the maintenance and manipulation of information. Orthodoxy holds the prefrontal cortex is more involved than parietal cortex in information manipulation (eg).
However, some have suggested that the spatial transformations…
developingintelligence | September 3, 2008Visual perception is constantly challenged by visual occlusion: objects in our environment constantly obscure one another, and seem to "disappear" when in fact they are nonetheless present.
Young infants begin to demonstrate a basic understanding of "object permanence" at some point during the first six months of life. On more complex tasks, understanding of object permanence is not observed until months later, as in Piaget's A-Not-B task. Even in these more demanding tasks, however, some understanding of object permanence can be revealed by the direction in which children gaze: kids will…
developingintelligence | September 2, 2008An absence of evidence is not itself evidence for the absence of a particular effect. This simple problem - generally known as the problem of null effects - yields many difficulties in cognitive science, making it relatively easier to parcellate cognitive and neural processes into ever-finer detail than to show when two processes are identical. Recently, this problem has emerged for the wonder child of cognitive science, functional magnetic resonance imaging (fMRI). The problem in this case is how to determine whether two tasks recruit at least one of the same areas of the brain in the…
developingintelligence | August 29, 2008Is it possible to form and execute motor intentions without being aware of when those intentions were formed? Precisely this pattern was observed by among (ha!) patients with parietal damage, as reported by Sirigu et al. They showed that patients with parietal damage are specifically impaired at estimating the time they formed the intention to commit a voluntary action, although they are unimpaired on other visual and temporal aspects to the task relative to healthy controls and to patients with cerebellar damage.
The authors argue that intentions formed in prefrontal cortex may be used…
developingintelligence | August 28, 2008Ideally, our real-world behavior is strongly determined by our context, for the simple reason that some behaviors are only appropriate in some situations (e.g., eating during an internal context of hunger, or using slang during an external context of casual interaction).
Context-inappropriate behavior is often seen as a failure of cognitive control (e.g., continuing to eat when no longer hungry, or using a common slang phrase in a formal setting).
This perspective is called "context processing," based on work pioneered by Todd Braver, Dianna Barch, Jon Cohen, and others. This framework is…
developingintelligence | August 27, 2008Parietal cortex is critical for the maintenance of object information over delays. This is true both in tests of working memory (e.g., 1, 2 and 3) as well as simple visual manipulations involving the occlusion of visible objects.
A great example is this study by Olson et al., who demonstrated that neurons in human intraparietal sulcus (IPS) and middle temporal (MT) cortex increased their activity in response to objects which disappeared due to occlusion (i.e., they were hidden behind another object) relative to those which simply disappeared without an occluder. This was particularly…
developingintelligence | August 26, 2008Andersen et al discuss both the attentional and intentional aspects to the function of the intraparietal sulcus. What's the distinction between attention and intention?
First, let's talk about attention. The modal view, based on the biased competition model of Desimone and Duncan, and the Miller & Cohen model presented yesterday, is probably that prefrontal regions actively bias particular spatial locations, as represented in parietal cortex, in accord with the current task or goal.
However, some evidence apparently conflicts with this modal view: Anderson et al. review two studies…
developingintelligence | August 25, 2008People often use the concept "hand-eye coordination" without appreciating its neural basis. Evidence collected by Andersen & colleagues over the past ten years indicates that different areas of parietal cortex are recruited to represent targets which require different effectors, all using a common eye-based coordinate system. Thus these areas are precisely those which contribute to "hand-eye coordination."
In a 1999 issue of Science, Batista, Buneao, Snyder & Andersen reported that 84% of neurons recorded from the "parietal reach region" of 3 macaques showed a peculiar pattern of…
developingintelligence | August 25, 2008In their already-classic 2001 article, Miller & Cohen use a "train track" metaphor to illustrate the function of prefrontal cortex. The idea is that myriad learned associations interconnect sensory representations with motor commands (metaphorically, these are the "train tracks"). The important associations will change depending on the animal's current task (these are the "switching stations" which allow crossover between the train tracks). Thus, the role of prefrontal cortex is to bias activity in the brain (the "train") to undergo the sensory-motor transformations which are task- and…
developingintelligence | July 15, 2008To enhance any system, one first needs to identify its capacity-limiting factor(s). Human cognition is a highly complex and multiply constrained system, consisting of both independent and interdependent capacity-limitations. These "bottlenecks" in cognition are reviewed below as a coherent framework for understanding the plethora of cognitive training paradigms which are currently associated with enhancements of working memory, executive function and fluid intelligence (1,2, 3, 4, 5, 6, 7, 8, 9,10, c.f. 11, 12, 13).
By far, the most common complaint about limitations in cognition is…