People who are more aware of their own heart-beat have superior time perception skills

What underlies our sense of time? A popular account claims an internal pacemaker emits regular pulses, which are detected by an accumulator. The amount of accumulated pulses represents the amount of time that's passed.

Trouble is, this is all very theoretical and no-one really knows how or where in the brain these functions are enacted. One suggestion is that the pulses are based on bodily feedback and in particular the heart-beat. Consistent with this is a recent brain imaging study that showed activity in the insular (a brain region associated with representing internal bodily states) rose linearly as people paid attention to time intervals (pdf). Now a behavioural study by Karin Meissner and Marc Wittmann has built on these findings by showing that people who are more sensitive to their own heart-beat are also better at judging time intervals.

Thirty-one participants listened to auditory tones of either 8, 14, or 20 seconds duration. After each one, they heard a second tone and had to press a button when they thought its duration matched the first. Counting was forbidden during the task and a secondary, number-based memory task helped enforce this rule. Heart-beat perception accuracy was measured separately and simply involved participants counting silently their own heart-beats over periods of 25, 35, 45 and 60 seconds.

The take away message is that the participants who were more in tune with their heart-beats also tended to perform better at the time estimation task. A further detail is that physiological measures taken during the encoding part of the task showed that as time went on, the participants' heart-rate slowed progressively, and their skin conductance (i.e. amount of sweat on the skin) reduced. Moreover, the rate of change in a participant's heart-rate (but not skin conductance) was linked with the accuracy of their subsequent time estimates.

'These results suggest that the processing of interoceptive signals [i.e. of internal bodily states] in the brain might contribute to our sense of time,' Meissner and Wittmann concluded.

The new findings add to past research showing that patients with cardiac arrhythmia are poorer than controls at time estimation tasks, and that drug-induced speeding or slowing of the autonomic nervous system (including heart-rate) affects people's under- or over-estimation of time intervals.
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Meissner, K., and Wittmann, M. (2011). Body signals, cardiac awareness, and the perception of time. Biological Psychology, 86 (3), 289-297 DOI: 10.1016/j.biopsycho.2011.01.001

Sweaty work in the hunt for the brain basis of social anxiety

Anxiety has overtaken depression to become the most commonly diagnosed psychological disorder in the United States, with social anxiety its most frequent manifestation. Part of the cause of extreme social anxiety is thought to be related to bad experiences - being laughed at in class, blushing in front of friends, choking on a first date - so that a person learns to fear social situations. But that's unlikely to be the whole story. Social anxiety runs in families suggesting some people have an innate predisposition for the disorder. The authors of a new study believe they've identified, for the first time, a neural correlate of this vulnerability.

Wen Zhou and colleagues scanned the brains of nineteen women while they were exposed to the smell of two types of men's sweat, a floral scent, and the human steroid (and putative pheromone) androstadienone. One of the male sweat types was sexual, the other was neutral, and they were collected from men's armpits as they watched either a sexual film or an educational documentary. The women weren't told what the different smells were or where they came from.

Human sweat is known to convey social signals. For example, it's been shown that people can tell a person's emotional state purely from the smell of their sweat. The key findings in this new study are that the two types of sweat, compared to the other odours, led to increased activation in the orbitofrontal cortex (OFC) of the women's brains, and that the level of this activation was related to the women's amount of self-reported trait social anxiety. The women didn't have any psychiatric diagnoses but the higher they scored on a measure of trait social anxiety (e.g. they said they felt uncomfortable in large groups), the less activation they exhibited in their OFC when exposed to the men's sweat.

It's important to emphasise that most of the women (nearly 90 per cent) didn't realise the smells were from humans, and the smells had no effect on their in-the-moment mood or anxiety levels. Consistent with this, the different smells didn't differentially affect the amygdala, a bilateral subcortical structure associated with fear processing. What the study appears to be showing is that subconscious social signals trigger increased OFC activity compared with nonsocial smells, and that the level of this activity is moderated by trait social anxiety.

Why the OFC? The OFC is heavily interconnected with the amygdala and is known to be involved in the learning of rewards and punishments and in decision-making. Another brain imaging study found that public speaking was associated with increased activation in the amygdala and reduced activation in the OFC. So it makes sense that people with a predisposition for social anxiety may have an OFC cortex that functions differently from those without such a disposition.

'Whether such inherent variations can be directly mapped onto genetic differences or personality traits in both normal and clinical populations, is an important open question and this deserves serious studies in the future,' the researchers said.
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Zhou, W., Hou, P., Zhou, Y., and Chen, D. (2010). Reduced recruitment of orbitofrontal cortex to human social chemosensory cues in social anxiety. NeuroImage DOI: 10.1016/j.neuroimage.2010.12.064

The Special Issue Spotter

We trawl the world's journals so you don't have to:

The role of touch in marketing (Psychology and Marketing).

International perspectives on stalking (Behavioural Sciences and the Law).

Narrative and psychotherapy (Psychotherapy Research).

Threat-Detection and Precaution: Neuro-physiological, Behavioral, Cognitive and Psychiatric Aspects (Neuroscience & Biobehavioral Reviews).

Executive Function (Journal of Experimental Child Psychology).

Personal relationships in late life (Journal of Social and Personal Relationships).

The Contribution of Systematic Case Study Research to Building an Evidence Base for Counselling and Psychotherapy (Counselling and Psychotherapy).