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Doubts cast on influential theory of visual processing

Psychologists in Germany have challenged one of the most influential theories in neuropsychology – the dual stream model of visual processing proposed by Mel Goodale and David Milner. This model (see tinyurl.com/b3ktap for Psychologist article) proposes that visual information entering the brain splits down two parallel paths: the dorsal path heads to the top and rear of the brain where the information is used for guiding actions; the ventral path reaches the temporal lobes where it is used for conscious perception and recognition. The model is hugely influential and will be familiar to all contemporary psychology graduates. The three seminal papers proposing and supporting the model have been cited over 930 times.

Much of the supporting evidence came from studies of the brain-damaged patient known in the literature as D.F. This woman’s damage to her occipital and parietal lobes from carbon monoxide poisoning appeared to have left her with a rare form of ‘visual agnosia’ – she was unable to recognise everyday objects but was perfectly able to grasp and use them. In other words, she appeared to have an impaired ventral stream but a preserved dorsal stream.

Marc Himmelbach and his team at Eberhard Karls University say that D.F. has become one of the most influential brain-damaged patients in neuropsychology, comparable to Paul Broca’s aphasic patient Leborgne and Phineas Gage – the 19th-century railway worker who survived an iron rod passing through his brain. However, as is the case with Leborgne and Gage, the German team believe that standards of testing have become more stringent since the seminal work with D.F. was published back in the 90s. In particular, conclusions were drawn about D.F. without comparing her performance and behaviour to age-matched controls.

For their paper, Himmelbach and his team have replicated the three main tests performed on D.F. with 20 female, age-matched healthy controls (mean age 36.5 years). These tests included indicating the size of various rectangular wooden blocks using the thumb and forefinger; actually reaching and picking up the blocks; indicating the orientation of a narrow slot in a disc; posting a card through that slot; and indicating the size and shape of odd-regular shapes and then actually picking up those shapes. Results from the original work with D.F. were compared against the results from these new healthy controls.

Himmelbach and his colleagues don’t dispute that D.F.’s performance was far more impaired for recognition tasks compared with the reaching and grasping tasks. However, compared against their new control data, they say it’s clear that D.F. was also severely impaired in her reaching and grasping performance, seemingly undermining the neat interpretation that she had a preserved dorsal stream. The German group also point to more recent tests of D.F. showing that she has obvious motor deficits when the task is more complicated – for example, she was unable to grasp a disc through three holes in its surface using her thumb, index and middle fingers.

Other evidence highlighted by Himmelbach and co concerns a more recently identified patient ‘J.S.’ who has a similar pattern of brain damage to D.F. and who is more impaired on recognition than motor tasks, but who nonetheless is clearly severely impaired on motor tasks compared with healthy controls. Based on a scan of J.S., the researchers also doubt that the pattern of brain damage suffered by D.F is as circumscribed as previously claimed. Finally, the researchers are critical of the lack of ‘kinematic data’ from the original tests of D.F. – things like reaction times, peak velocity of movements and so forth. Such data, they say, would show whether her movements were really normal, or if she were, for example, taking longer than normal to compensate for her difficulties.

‘In conclusion,’ the researchers said, ‘the behaviour and anatomy of D.F. on its own does not provide firm grounds for the perception vs. action interpretation of dorsal and ventral stream areas.’ They added that other sources of support for the dual stream model ‘do not provide unequivocal evidence in favour of or against [the model] without reference to D.F. and could also be integrated by alternative models that do not explicitly state an action–perception dissociation.’


Lost sleep and cyberloafing
In the Journal of Applied Psychology (see tinyurl.com/85t7359)

When the clocks went forward at the end of March, did you have an urge to watch the 1982 snooker championship final on the internet at work the following day? A new article suggests that we may be more prone to ‘cyberloafing’, frittering away work time on unrelated online activities, when we haven’t had enough sleep.

The researchers, led by David Wagner, began sifting through Google’s publicly available data for rates of entertainment-related searches, judged to be a proxy of cyberloafing. Usinga ‘quasi experimental’ approach, the investigators recognised an event that affects everyone’s sleep: when the clocks go forward for Daylight Saving Time. Prior evidence suggests we lose on average 40 minutes of sleep per night following the switch, as our body rhythms struggle to adjust. The researchers used data from 203 metropolitan areas in the USA, weighted by area size, across 2004–2009. They found that entertainment-related searches on the Monday after DST were 3.1 per cent higher than on the Monday before, and 6.4 per cent higher than on the Monday after.

A second study took this to controlled lab conditions. Ninety-six undergraduate students wore a sleep-monitoring bracelet overnight before attending a lab session to complete a computer task – assessing a potential new professor for the university by watching a 42-minute video lecture. What the researchers were really interested in was the amount of time they would spend surfing the internet instead. Cyberloafing was higher for participants who experienced more instances of sleep interruption or less sleep overall, as recorded by their monitoring bracelet.

This is another piece of research advancing the ego depletion theory, which states that willpower is a resource that is used up through effortful acts. Researchers have previously argued that sleep is a means of recharging our regulatory resources, and these studies confirm that less sleep does indeed make us prey to counterproductive activities like cyberloafing. However, those who naturally exercise self-discipline may be somewhat resistant: in study two, the effect of sleep interruption on cyberloafing was weaker for participants who scored high on a measure of conscientiousness administered beforehand. (The effect of less overall sleep still remained.) This is consistent with ego depletion, as highly conscientious types are more likely to actively use methods to regulate their effort to overcome counterproductive behaviours, rather than taking the path of least resistance.

The costs of cyberloafing have been estimated at around £300m a year, so it’s worth understanding when we're more vulnerable to its temptations.

I    This item is from the Society’s Occupational Digest, written and edited by Dr Alex Fradera – see www.occdigest.org.uk and follow @occdigest.

Easily embarrassed and altruistic
In the January issue of the Journal of Personality and Social Psychology

like walking a tight-rope, an excruciating pit of embarrassment always just one tiny misstep away. But could embarrassment also function in our favour, helping to advertise some of our better, more desirable qualities?

Matthew Feinberg and his colleagues at the University of California, Berkeley conducted five experiments in total, involving hundreds of undergrad participants. The first two studies were designed to test whether people who experience more embarrassment are more prosocial. In the first, participants were video-recorded as they recounted a time they’d been embarrassed. The videos were coded and it was found that the students who displayed more signs of embarrassment (e.g. gaze aversion, nervous face touching and laughter) also tended to endorse values of fairness more, and they were actually more generous with money in an economic game. In the second study, participants who said they would be more embarrassed in a range of hypothetical social scenarios tended to be more generous in an economic game, and they also scored more highly on a questionnaire measure of their prosociality.

Further studies tested whether embarrassed people are perceived as more prosocial. It was found that individuals who had appeared more embarrassed in the videos from the first study were rated as more prosocial by new participants. Another set of participants rated actors displaying an expression of embarrassment as more prosocial than those displaying pride or a neutral expression. Still more participants agreed to cooperate more fully in an economic game with people who they’d seen pictured looking embarrassed.

A fifth and final study was the most realistic. Participants saw their research partner praised for his or her superb performance on a mental performance test. Unbeknown to the participants, their partner was an accomplice of the researchers. On being praised, this actor either responded with embarrassment or with pride. Crucially, later on, the participants tended to cooperate more with their partner if he or she had shown embarrassment earlier, as opposed to pride. What’s more, the greater the intensity of their partner’s earlier display of embarrassment, the more participants tended to trust and cooperate with him or her. The researchers also ruled out the possibility that the actor was displaying shame, rather than embarrassment. One final important detail: the researchers checked and these effects of embarrassment weren’t because the participants saw their embarrassed partner as weak, liked them more, or because they felt compassion towards them.

‘Our data are the first to reveal that people who feel and show intense embarrassment are indeed more prosocial,’ the researchers concluded, ‘and that this display triggers prosocial inferences and actions.’ The researchers said there was a need for more research – for example, to find out whether it’s possible for people to feign embarrassment and thereby benefit from the flattering assumptions onlookers make about them.

The material in this section is taken from the Society’s Research Digest blog at www.researchdigest.org.uk/blog, and is written by its editor Dr Christian Jarrett. Visit the blog for full coverage including references and links, additional current reports, an archive, comment and more.

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