cognitive neuroscience
developingintelligence | April 26, 2007People are remarkably bad at switching tasks - and research focusing on this fact has isolated a network of brain regions that are involved in task-switching (I'll call it the "frontal task network" for short). One of the stranger findings to emerge from this literature is the fact that we're actually worse at switching to a more natural or well-practiced task after having performed a less natural one.
One potential explanation for this "switch cost asymmetry" is that the task network may recognize the potential for errors when performing the unnatural task, and therefore "help it along"…
developingintelligence | April 25, 2007A lack of clear definitions for terms like "intelligence" and "consciousness" plagues any serious discussion of those concepts. A recent article by Seth, Baars & Edelman argues for a core set of 17 properties that are characteristic of consciousness, and could be used in the "diagnosis" of consciousness in humans and other animals.
Property 1: "Irregular" patterns of brain activity
Electrical oscillations occuring between 20 and 70 times per second are common in awake humans, but epilepsy, sleep, anesthesia and some forms of brain damage are accompanied by the dominance of highly regular…
developingintelligence | April 24, 2007Ever heard that "you're born with all the brain cells you'll ever have"? It turns out that could be a good thing - if it were true. A new study shows that at least in some circumstances, neurogenesis actually impairs memory performance.
To understand why this might be the case, consider that adults are constantly generating new neurons in a long-term memory structure - the hippocampus. This region requires a large number of neurons to store episodic memories accumulated over a lifetime (and understandably so!). Similarly, to be able to store experiences that may have occurred very…
developingintelligence | April 20, 2007Have you ever momentarily forgotten the name of a specific place, or person, despite being able to recall many things about the name (for example the first few letters, or the number of syllables)? Chances are, if you've experienced this "tip-of-the-tongue" phenomenon, you've also had the word spontaneously occur to you minutes or hours later. One explanation for this fascinating failure of memory is retrieval-induced forgetting, in which the retrieval of closely related concepts and words actually competes with the word or concept you intended to retrieve (discussed previously). The…
developingintelligence | April 16, 2007Among nature's most impressive feats of engineering is the remarkably flexible and self-optimizing quality of human cognition. People seem to dynamically determine whether speed or accuracy is of utmost importance in a certain task, or whether they should continue with a current approach or begin anew with another, or whether they should rely on logic or intuition to solve a certain problem. A topic of intense research in cognitive neuroscience is how cognition can be made so flexible.
One possibility proposed by by Brown, Reynolds & Braver is that cognitive control is multi-faceted, in…
developingintelligence | April 11, 2007Very early in the history of artificial intelligence research, it was apparent that cognitive agents needed to be able to maximize reward by changing their behavior. But this leads to a "credit-assignment" problem: how does the agent know which of its actions led to the reward? An early solution was to select the behavior with the maximal predicted rewards, and to later adjust the likelihood of that behavior according to whether it ultimately led to the anticipated reward. These "temporal-difference" errors in reward prediction were first implemented in a 1950's checker-playing program,…
developingintelligence | April 10, 2007Right now, you're blind at one particular part of your visual field - because you have no photoreceptors at the location on your retina where the optic nerve begins its journey to visual cortex. Normally, you're unaware of this blind spot because of perceptual "filling-in" - a mechanism by which your brain actively fabricates the perceptual data it's missing.
But this isn't the only case where cognition manufactures perception. In the case of the Kanizsa triangle, you will sense the presence of a full triangle although none truly exists. In other words, your brain has fabricated "illusory…
developingintelligence | April 9, 2007Given a fixed amount of computational power in designing an intelligent system, there is a necessary tradeoff between how many resources are devoted solely to the current task, and how many resources are devoted to monitoring for information that may be important but is not necessarily relevant to the current task. If more resources are dedicated to the current task, it may be accomplished more quickly - but at the same time, this setting may make it more difficult to reorient and switch to a different task. On the other hand, if more resources are dedicated to monitoring or reorienting,…
developingintelligence | April 5, 2007"To understand ourselves, we must embrace the alien." - PZ Meyers
One difficulty in understanding consciousness is the fact that we know of only one species that certainly possesses it: humans. A new article by Jennifer Mather suggests that octopi may also possess consciousness, despite the vastly different architecture of their brain. If two very different neural architectures can both support forms of advanced cognition, then the similarities between them may help clarify the computational requirements for intelligent behavior.
Octopus brains are striking different from those in primates…
developingintelligence | April 4, 2007"Instead of trying to produce a programme to simulate the adult mind, why not rather try to produce one which simulates the child's?" - Alan Turing (Computing Machinery, p456)
One of the defining features of childhood cognition is "behaving without thinking." Not surprisingly, developmental cognitive psychology has latched onto the idea of impulse control - and other processes putatively requiring inhibition - as a central explanatory construct, playing a role in attention deficit disorder, post-traumatic stress disorder and everything in between (including developmental trends in normal…
developingintelligence | April 3, 2007How does the brain exert flexible control over behavior? One idea is that high-level areas of the brain self-organize representations that lead to reward in a certain task, in a sense by "programming" or "executing" a pattern of activity that controls activity in more posterior and domain-specific regions (i.e., sensory or motor cortex). This portrays prefrontal cortex as a kind of field-programmable gate array, which can be dynamically reconfigured on the basis of dopaminergic reward signals, so as to perform different computations at will.
Concrete evidence for this view is provided by…
developingintelligence | April 2, 2007Everyone does something they later regret. Can you ever intentionally forget that you did it? The idea of memory repression has rarely been considered within scientific psychology, but the processes involved in intentional forgetting (also covered last week) are the focus of a recent article by Michael Anderson.
In his article, Anderson argues that the "cognitive control" required to suppress an unwanted memory is fundamentally similar to the processes involved in overcoming a habitual or "prepotent" response in favor of a weaker response. A simple example might be naming the ink color of…
developingintelligence | March 27, 2007"A good metaphor is something even the police should keep an eye on." - G.C. Lichtenberg
Although the brain-computer metaphor has served cognitive psychology well, research in cognitive neuroscience has revealed many important differences between brains and computers. Appreciating these differences may be crucial to understanding the mechanisms of neural information processing, and ultimately for the creation of artificial intelligence. Below, I review the most important of these differences (and the consequences to cognitive psychology of failing to recognize them): similar ground is…
mixingmemory | March 27, 2007Research on the role of emotion/intuition in moral judgments is really heating up. For decades (millennia, even), moral judgment was thought to be a conscious, principle-based process, but over the last few years, researchers have been showing that emotion and intuition, both of which operate automatically and unconsciously for the most part, play a much larger role than most philosophers and psychologists had previously been willing to admit. In this context, two recent papers by roughly the same group of people have presented some really interesting findings which, if you ask me (and if you…
developingintelligence | March 23, 2007The past continuously besets our ability to act flexibly in the future; habits grow strong, automaticity takes over and the mind wanders. Before you know it, you've forgotten to stop for milk on your regular commute, neglected to go to your dentist appointment, or merely "lost track" of what you were doing. These kinds of things are often studied in cognitive control laboratories, usually in the context of a task where there is particularly strong "proactive interference" from previous habits (for example, the habit to read color-words instead of naming ink-colors in the Stroop task).
A…
developingintelligence | March 22, 2007Imagine you are invisible. Congratulations, you are now actually less likely to remember what you were doing a few minutes ago, and possibly a lot longer ago than that. At least, this is the basic finding from a 2002 article by Sahakyan & Kelley, who showed that when people are asked to forget something they'd learned, they may actually do this by rapidly changing their internal context in a way that is similar to what happens if, say, you're asked to imagine that you're invisible.
In the laboratory, this is usually studied in the "directed forgetting paradigm," in which subjects learn…
developingintelligence | March 21, 2007In the new issue of Seed, Douglas Hofstadter talks about "strange loops" - his term for patterns of level-crossing feedback inside some medium (such as neurons) - and their role in consciousness. Likewise, Gerald Edelman has talked about how a "reentrant dynamic core" of neural activity could tightly integrate large groups of neurons through positive feedback cycles. Similarly, many view interactions among neural oscillations as a candidate mechanism for the formation of consciousness - such oscillations can perform abstract computations (as in liquid state machines) and can interact with…
developingintelligence | March 20, 2007Imagine that you are about to pass to a teammate when he suddenly darts in another direction, in an attempt to get clear. With some difficulty, you will be able to modify your pass and correctly throw the ball to your teammate's new location. How is this process implemented in the brain? This scenario relies on quick processing of relevant perceptual information in order to modify or interrupt the ongoing motor commands, which itself requires a tight linkage between perception and action - yet another unsolved "binding problem" in cognitive neuroscience (as covered yesterday).
One form of…
developingintelligence | March 19, 2007Last week I discussed how central dopamine levels appear to correlate with how strongly actions are bound to particular visual features. I presented this as part of "the binding problem," but in fact the topic runs must deeper: cognitive neuroscience has yet to reveal the mechanisms by which the motor system "links up" with the perceptual system. This is the topic covered by Verleger et al's 2005 J. Psychophysiology article, which points not to dopamine, nor to multiplexed neural synchrony, but rather to the "P3b" component of scalp electrical activity as the "glue" that binds together…
mixingmemory | March 18, 2007With a paper by Freedberg and Gallese, to be published in Trends in Cognitive Sciences, mirror neurons have made their way into neuroaesthetics (at some point, someone like Gallese will publish a paper arguing that mirror neurons explain everything, and we'll begin to wonder what the hell the rest of the brain is for). Here's the abstract from the paper1:
The implications of the discovery of mirroring mechanisms and embodied simulation for empathetic responses to images in general, and to works of visual art in particular, have not yet been assessed. Here, we address this issue and we…