A new study has found that errors in perceptual decisions occurred only when there was confused sensory input, not because of any ‘noise’ or randomness in the cognitive processing. The finding, if replicated across broader contexts, will change some of our fundamental assumptions about how the brain works.

The study unusually involved both humans and rats — four young adults and 19 rats — who listened to streams of randomly timed clicks coming into both the left ear and the right ear. After listening to a stream, the subjects had to choose the side from which more clicks originated.

The errors made, by both humans and rats, were invariably when two clicks overlapped. In other words, and against previous assumptions, the errors did not occur because of any ‘noise’ in the brain processing, but only when noise occurred in the sensory input.

The researchers supposedly ruled out alternative sources of confusion, such as “noise associated with holding the stimulus in mind, or memory noise, and noise associated with a bias toward one alternative or the other.”

However, before concluding that the noise which is the major source of variability and errors in more conceptual decision-making likewise stems only from noise in the incoming input (in this case external information), I would like to see the research replicated in a broader range of scenarios. Nevertheless, it’s an intriguing finding, and if indeed, as the researchers say, “the internal mental process was perfectly noiseless. All of the imperfections came from noise in the sensory processes”, then the ramifications are quite extensive.

The findings do add weight to recent evidence that a significant cause of age-related cognitive decline is sensory loss.

[3376] Brunton BW, Botvinick MM, Brody CD. Rats and Humans Can Optimally Accumulate Evidence for Decision-Making. Science [Internet]. 2013 ;340(6128):95 - 98. Available from:

A study has found that brain regions responsible for making decisions continue to be active even when the conscious brain is distracted with a different task.

The study, in which 27 adults were given information about cars and other consumer products then asked to perform a brief but challenging working memory task (involving numbers) before making their decision about the items, found that:

  • As shown previously, the brief period of distraction (two minutes) produced higher quality decisions.
  • Regions activated during the learning phase (right dorsolateral prefrontal cortex and left intermediate visual cortex) continued to be active during the distractor task.
  • The amount of activation within the visual and prefrontal cortices during the distractor task predicted the degree to which participants made better decisions (activity occurring during the working memory task, as shown by a separate performance of that task, was subtracted from overall activity).

[3394] Creswell DJ, Bursley JK, Satpute AB. Neural Reactivation Links Unconscious Thought to Decision Making Performance. Social Cognitive and Affective Neuroscience [Internet]. 2013 . Available from:

Matching patterns of sales data for lottery games in one American county for a year against daily temperature has revealed that sales for scratch tickets (many options to select) fell by nearly $600 with every 1° Fahrenheit increase in temperature. On the other hand, sales for lotto tickets, which require fewer decisions, were not affected.

Following this finding up with a series of lab experiments, researchers found that increases of a mere 5°F in temperature (against the ‘most comfortable’ 72°) significantly reduced cognitive performance on a variety of cognitive tasks (proofreading; choosing between two cell phone plans; choosing between an innovative or a traditional product).

It is suggested that warmer temperatures, which require our body to exert cooling efforts, deplete glucose levels (interestingly, cooling ourselves down is apparently more effortful than warming ourselves up), leaving less energy available for cognition.

[3335] Cheema A, Patrick VM. Influence of Warm Versus Cool Temperatures on Consumer Choice: A Resource Depletion Account. Journal of Marketing Research [Internet]. 2012 ;49(6):984 - 995. Available from:

Research has shown that younger adults are better decision makers than older adults — a curious result. A new study tried to capture more ‘real-world’ decision-making, by requiring participants to evaluate each result in order to strategize the next choice.

This time (whew!), the older adults did better.

In the first experiment, groups of older (60-early 80s) and younger (college-age) adults received points each time they chose from one of four options and tried to maximize the points they earned.  For this task, the younger adults were more efficient at selecting the options that yielded more points.

In the second experiment, the rewards received depended on the choices made previously.  The “decreasing option” gave a larger number of points on each trial, but caused rewards on future trials to be lower. The “increasing option” gave a smaller reward on each trial but caused rewards on future trials to increase.  In one version of the test, the increasing option led to more points earned over the course of the experiment; in another, chasing the increasing option couldn’t make up for the points that could be accrued grabbing the bigger bite on each trial.

The older adults did better on every permutation.

Understanding more complex scenarios is where experience tells. The difference in performance also may reflect the different ways younger and older adults use their brains. Decision-making can involve two different reward learning systems, according to recent thinking. In the model-based system, a cognitive model is constructed that shows how various actions and their rewards are connected to each other. Decisions are made by simulating how one decision will affect future decisions. In the model-free system, on the other hand, only values associated with each choice are considered.

These systems are rooted in different parts of the brain. The model-based system uses the intraparietal sulcus and lateral prefrontal cortex, while the model-free system uses the ventral striatum. There is some evidence that younger adults use the ventral striatum (involved in habitual, reflexive learning and immediate reward) for decision-making more than older adults, and older adults use the dorsolateral prefrontal cortex (involved in more rational, deliberative thinking) more than younger adults.

We learn from what we read and what people tell us, and we learn from our own experience. Although you would think that personal experience would easily trump other people’s advice, we in fact tend to favor abstract information against our own experience. This is seen in the way we commonly distort what we experience in ways that match what we already believe. But there is probably good reason for this tendency (reflected in confirmation bias), even if it sometimes goes wrong.

But of course individuals vary in the extent to which they persist with bad advice. A new study points to genes as a critical reason. Different brain regions are involved in the processing of these two information sources (advice vs experience): the prefrontal cortex and the striatum. Variants in the genes DARPP-32 and DRD2 affect the response to dopamine in the striatum. Variation in the gene COMT, on the other hand, affects dopamine response in the prefrontal cortex.

In the study, over 70 people performed a computerized learning task in which they had to pick the "correct" symbol, which they learned through trial and error. For some symbols, subjects were given advice, and sometimes that advice was wrong.

COMT gene variants were predictive of the degree to which participants persisted in responding in accordance with prior instructions even as evidence against their correctness grew. Variants in DARPP-32 and DRD2 predicted learning from positive and negative outcomes, and the degree to which such learning was overly inflated or neglected when outcomes were consistent or inconsistent with prior instructions.

The study involved 26 experienced Buddhist meditators and 40 control subjects. Scans of their brains while they played the "ultimatum game," in which the first player proposes how to divide a sum of money and the second can accept or reject the proposal, revealed that the two groups engaged different parts of the brain when making these decisions.

Consistent with earlier studies, controls showed increased activity in the anterior insula (involved in disgust and emotional reactions to unfairness and betrayal) when the offers were unfair. However the Buddhist meditators showed higher activity instead in the posterior insula (involved in interoception and attention to the present moment). In other words, rather than dwelling on emotional reactions and imaginary what-if scenarios, the meditators concentrated on the interoceptive qualities that accompany any reward, no matter how small.

The meditators accepted unfair offers on more than half of the trials, whereas controls only accepted unfair offers on a quarter of the trials.

Moreover, those controls who did in fact play the game ‘rationally’ (that is, mostly accepting the unfair offers) showed activity in the dorsolateral prefrontal cortex, while rational meditators displayed increased activity in the somatosensory cortex and posterior superior temporal cortex.

The most intriguing thing about all this is not so much that regular meditation might change the way your brain works (although that is undeniably interesting), but as a more general demonstration that we can train our brain to work in different ways. Something to add to the research showing how brain regions shift in function in those with physical damage to their brains or sense organs (eg, in those who become blind).

There’s been a lot of discussion, backed by some evidence, that groups are ‘smarter’ than the individuals in them, that groups make better decisions than individuals. But it is not, of course, as simple as that, and a recent study speaks to the limits of this principle. The study involved pairs of volunteers who were asked to detect a very weak signal that was shown on a computer screen. If they disagreed about when the signal occurred, then they talked together until they agreed on a joint decision. The results showed that joint decisions were better than the decision made by the better-performing individual (as long as they could talk it over).

However, when one of the participants was sometimes surreptitiously made incompetent by being shown a noisy image in which the signal was much more difficult to see, the joint decisions were worse than the decisions of the better performing partner. In other words, working with others can have a detrimental effect if one person is working with flawed information, or is incompetent but doesn't know it. Successful group decision-making and problem-solving requires the participants to be able to accurately judge their level of confidence.

It’s now well established that older brains tend to find it harder to filter out irrelevant information. But now a new study suggests that that isn’t all bad. The study compared the performance of 24 younger adults (17-29) and 24 older adults (60-73) on two memory tasks separated by a 10-minute break. In the first task, they were shown pictures overlapped by irrelevant words, told to ignore the words and concentrate on the pictures only, and to respond every time the same picture appeared twice in a row. The second task required them to remember how the pictures and words were paired together in the first task. The older adults showed a 30% advantage over younger adults in their memory for the preserved pairs. It’s suggested that older adults encode extraneous co-occurrences in the environment and transfer this knowledge to subsequent tasks, improving their ability to make decisions.

[276] Campbell KL, Hasher L, Thomas RC. Hyper-binding: a unique age effect. Psychological Science: A Journal of the American Psychological Society / APS [Internet]. 2010 ;21(3):399 - 405. Available from:

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A study involving 54 older adults (66-76) and 58 younger adults (18-35) challenges the idea that age itself causes people to become more risk-averse and to make poorer decisions. Analysis revealed that it is individual differences in processing speed and memory that affect decision quality, not age. The stereotype has arisen no doubt because more older people process slowly and have poorer memory. The finding points to the need to identify ways in which to present information that reduces the demand on memory or the need to process information very quickly, to enable those in need of such help (both young and old) to make the best choices. Self-knowledge also helps — recognizing if you need to take more time to make a decision.

Several reports have come out in recent years on how recent events replay in the hippocampus, a process thought to be crucial for creating long-term memories. Now a rat study suggests that these replays are not merely echoes of past events, but a dynamic process aimed at improving decision-making. Rather than being solely replays of recent or frequent paths through the maze, the replays were often paths that the rats had rarely taken or, in some cases, had never taken, as if the rats were trying to build maps to help them make better navigation decisions.

Older news items (pre-2010) brought over from the old website

Sleep deprivation can threaten competent decision-making

An imaging study follows research showing that sleep-deprived participants engaged in a gambling task choose higher-risk decks and exhibit reduced concern for negative consequences. The study reveals that sleep deprived adults asked to make decisions in a gambling task show higher selective activity in the nucleus accumbens (involved with the anticipation of reward), and reduced activity in the insula (involved with evaluating the emotional significance of an event). The findings help explain why we make poorer decisions when sleep deprived.

Venkatraman, V., Chuah, Y.M.L., Huettel, S.A. & Chee, M.W.L. 2007. Sleep Deprivation Elevates Expectation of Gains and Attenuates Response to Losses Following Risky Decisions. Sleep, 30 (5), 603-609.

Exercise improves attention and decision-making among seniors

An imaging study involving adults ranging in age from 58 to 78 before and after a six-month program of aerobic exercise, found specific functional differences in the middle-frontal and superior parietal regions of the brain that changed with improved aerobic fitness. Consistent with the functions of these brain regions, those who participated in the aerobic-exercise intervention significantly improved their performance on a computer-based decision-making task. Those doing toning and stretching exercises did increase activation in some areas of the brain but not in those tied to better performance. Their performance on the task was not significantly different after the exercise program. The aerobic exercise used in the study involved gradually increasing periods of walking over three months. For the final three months of the intervention program, each subject walked briskly for 45 minutes in three sessions each week.

Colcombe, S.J., Kramer, A.F., Erickson, K.I., Scalf, P., McAuley, E., Cohen, N.J., Webb, A., Jerome, G.J., Marquez, D.X. & Elavsky, S. 2004. Cardiovascular fitness, cortical plasticity, and aging. PNAS, 101, 3316-3321. Published online before print as 10.1073/pnas.0400266101