developingintelligence | May 12, 2008Time pervades our understanding of the world - we use it to coordinate our movements, to perceive motion, to plan our behaviors, and perhaps even to understand causality.
But it is an under-appreciated factor in cognition. Even in the domain of the well-understood visual system, few realize that neurons in visual cortex are tuned not only for sensitivity to visual input of particular orientations, but also tuned also to time - in terms of temporal contrast.
Johnston, Arnold and Nishida were able to manipulate this temporal tuning with a relatively simple method. The authors presented a…
developingintelligence | May 9, 2008Our ability to suppress unwanted thoughts and behaviors is thought to be related to a process known as "inhibition," whereby ventrolateral regions of prefrontal cortex (vlPFC) actively suppress inappropriate representations. A 2001 study by Sakagami et al. recorded firing data from neurons in the vlPFC to determine the exact mechanism by which this might occur.
The authors begin by noting that previous studies of vlPFC have found that a majority of neurons "responded to a stimulus that instructed execution, not suppression, of a behavioral response." This view is consistent with that of…
developingintelligence | May 8, 2008Does the resolution or precision of human memory change with its available capacity? In other words, can you remember fewer items with greater precision than you can remember more items?
Contradicting intuition, a new paper from yesterday's issue of Nature shows that all items are stored in memory with equal resolution, regardless of the number of items stored. Authors Zhang & Luck first showed that subjects are equally accurate in reporting the color of a memorized item regardless of the number of other items being maintained in memory. Specifically, when subjects were asked to…
developingintelligence | May 7, 2008Complex cognition can be predicted by remarkably simple tasks. For example, the speed with which you choose one of two possible responses can reliably predict IQ. Some theories propose that this relationship is due to differences in something called "processing speed," but more recent work has shown the effect is really due to the slowness of your slowest reaction times on such simple tasks. Known as the "worst performance rule," this can be revealed through various RT distribution decomposition techniques (e.g., "binning" of reaction times or ex-gaussian analysis).
A particular class of…
developingintelligence | March 4, 2008Almost everyone tries to lose weight at some point, but we are remarkably bad at it; most people quickly return to their original weight after cessation of exercise or resumption of a normal diet. A review article by Patterson & Levin elucidates the pathways for this effect, and in the process finds a special role for juvenile exercise in guarding against obesity throughout the lifespan.
Patterson & Levin review several reasons for why it's so difficult to lose weight. First, caloric restriction is associated with subsequent "compensatory" increases in food intake, in both humans…
developingintelligence | February 25, 2008How does the human brain construct intelligent behavior? Computational models have proposed several mechanisms to accomplish this: the most well known is "Hebbian learning," a process mathematically similar to both principal components analysis and Bayesian statistics. But other neural learning algorithms must exist - how else could the brain disentangle mere correlations from true causation?
Temporal precedence helps to some extent - and does seem to play a large role in Hebbian learning (e.g., spike-timing dependent plasticity). But the smell of rain does not actually cause rain -…
developingintelligence | February 14, 2008Well, it's not quite as erotic as it sounds, but they could break the ice on more than a few Valentine's dates. Hayward's new article in Brain Research Bulletin describes all known tactile illusions. Some can be tried easily at home, but can work better when your gaze is averted and if someone else is performing these illusions on you (to reduce proprioceptive feedback):
The Aristotle: an object touched with crossed fingers will sometimes be identified as two objects (try it on your nose)
Comb: With a comb and a pencil, lay your index finger along the ends of the comb's teeth; use the pencil…
developingintelligence | February 11, 2008Caffeine is the most widely used stimulant in the world, but few use it to maximal advantage. Get optimally wired with these tips.
1) Consume in small, frequent amounts.
Between 20-200mg per hour may be an optimal dose for cognitive function.
Caffeine crosses the blood-brain barrier quickly (owing to its lipid solubility) although it can take up to 45 minutes for full ingestion through the gastro-intestinal tract. Under normal conditions, this remains stable for around 1 hour before gradually clearing in the following 3-4 hours (depending on a variety of factors).
A landmark 2004 study…
developingintelligence | February 5, 2008We often assume that true understanding is conveyed through spoken speech rather than gesture, but new research shows that "talking with your hands" can not only reveal different information than spoken language, it can be both more correct and yield better learning.
Goldin-Meadow and colleagues have previously shown that spontaneous gesture during speech contains a form of implicit knowledge - knowledge that cannot be verbally reported, but nonetheless affects performance. Similar phenomena are known as knowledge-action dissociations; for example, in Piagetian conservation tasks, children…
developingintelligence | February 4, 2008When do we learn to imagine the future, and how is that capacity based on imagining the past? How does this kind of "mental time travel" develop? Lagatutta's recent article in Child Development tracks the development of this impressive feat, thought by some to be uniquely human.
At 3 years of age, a variety of mental processes seem to undergo rapid development, including task-switching, theory of mind, linguistic generalization, and an understanding of time. Previous work by Lagatutta and colleagues showed that up to 39% of 3 year olds could attribute sadness in a story's character to that…
developingintelligence | January 11, 2008One of the bottlenecks in human memory capacity is its "filtering efficiency" - irrelevant information in memory only detracts from an already-constrained memory span. New work by McNab & Klingberg images the neural structure directly responsible for such filtering, and shows it can predict behavioral measures of memory span. Impressively, the location of this "memory filter" is the globus pallidus, as predicted by a computational network model of cortex, but in contrast to that model, it shows functional correlations with parietal in addition to frontal areas. This work has immediate…
developingintelligence | January 10, 2008A new educational system called "Tools of the Mind" teaches not facts and figures, but rather focuses on cognitive skills in structured play. In the largest and most compelling study yet, exposure to this curriculum in the classroom drastically improves performance on a variety of psychometric and neuropsychological tests.
Vygotskian theory posits that children need to "learn to learn" - by mastering a set of mental tools which bootstrap their mental abilities, the same way that physical tools can extend physical abilities. The consequent "mental exercise" may strengthen the mind just like…
developingintelligence | January 7, 2008A continuing challenge in cognitive neuroscience is determining which neural structures are actually responsible for certain thoughts and behaviors. For example, fMRI and other neuroimaging techniques cannot tell us if a certain region of visual cortex is necessary for perceiving motion, or if it is merely coactivated whenever motion is perceived. Such distinctions are both particularly important and particularly difficult to achieve in domains thought to be uniquely human: we cannot simply lesion human brains and observe the consequences as we can with animals trained to perform lower-…
developingintelligence | January 3, 2008Over New Year's I had a brief discussion with a condensed-matter physicist who proclaimed that 1) "some developmental research is amazingly bad" and that 2) "they think they can tell what a baby has learned from what direction it looks," topping it all off with 3) "you guys don't even know what learning is!"
I won't argue with the first point (there are bad researchers in every field, even condensed matter physics), and I'm too lazy to bother with the third (although the 2000 Nobel prize committee might disagree), but the second point - on the technique of preferential looking - I just can't…
developingintelligence | January 2, 2008Play is more often simply observed than studied scientifically - play behaviors occur unpredictably and, when they do occur, are highly chaotic, making it very difficult to study them in the laboratory. Despite these challenges, new work is beginning to make play accessible from a rigorous scientific framework.
For example, a recent article by Schulz & Bonawitz takes Piaget's notion of play as a mechanism for understanding causal relationships and recasts it into a testable prediction: children should be more likely to play with an object about which they have incomplete or confounded…
developingintelligence | December 13, 2007If you encounter a difficult situation, you may be extra careful afterwards, even in a different or unrelated situation. This intuitive statement has recently been confirmed in a laboratory task, and extended to show that such carry-over "conflict adaptation" effects may affect the speed with which you approach subsequent tasks very differently from how it affects the probability of making a mistake.
A task often used to look at conflict is the flanker task: when subjects must respond to an arrow symbol that is surrounded by other arrow symbols, responses will be faster when the surrounding…
Dispute Over the Canonical Cortical Circuit: Structure-Function Dissociations in the Cortical Column
developingintelligence | December 10, 2007Is there a basic "computational unit" of the neocortex? In contrast to subcortical regions, neocortical architecture seems fairly regular and matrix-like - leading to it's other name, "isocortex." While there are many contenders for the title of the "canonical circuit" or "cortical algorithm", few would dispute that cortical columns are a fundamental organizational principle of cortex.
Or wouldn't they? In their new Neuron article, Douglas & Martin's argue that the cortical column is a poor contender for identifying the cortex's "canonical circuit." They describe how the anatomical…
developingintelligence | December 3, 2007Your IQ can be reliably predicted by simple reaction time tasks - perhaps even more reliably than with much more complex cognitive tasks. This surprising psychometric fact has led to the belief in human "processing speed." In the same way that a computer with a faster microprocessor might carry out more computations, with potentially less demand on memory, the idea is that brains with better neuronal efficiency also manifest both higher IQ and proportionately faster reaction times even in simple tasks.
To me, this story always seemed "too good to be true" - or perhaps merely "too simple to…
developingintelligence | November 29, 2007The world wide web can be understood as a giant matrix of associations (links) between various nodes (web pages). At an abstract level, this is similar to human memory, consisting of a matrix of associations (learned relationships, or neuronal connections) between various nodes (memories, or the distributed representations constituting them). In the new issue of Psych. Science, Griffiths et al. ask whether Google's famously accurate and fast PageRank algorithm for internet search might behave similarly to the brain's algorithm - whatever that might be - for searching human memory.
About…
developingintelligence | November 29, 2007The ability to actively maintain more information in memory, known as "working memory," seems to benefit performance in a variety of tasks. One idea is that these tasks require controlled attention, allowing for better control over behavior.
But there's a serious problem with this explanation: maybe this doesn't reflect improved control so much as superior motivation. In other words, maybe subjects with higher working memory are the only ones who care, and everyone else is just goofing off!
Thankfully, there are some cases where additional working memory has no benefit - or can even be a…