Recently Language Hat asked for informed reactions to a BBC report claiming that Reading Arabic 'hard for brain'. The papers under discussion are to be found at Eviatar's home page, in particular the 2009 paper "Language status and hemispheric involvement in reading: Evidence from trilingual Arabic speakers tested in Arabic, Hebrew, and English" but also clearly the 2004 paper "Orthography and the hemispheres: Visual and linguistic aspects of letter processing". Now I'm no psycholinguist, but obviously this story smells fishy, so I had a closer look.
At least one glaring mistake seems to be clearly the BBC's fault: it wrongly claims "When the Arabic readers saw similar letters with their right hemispheres, they answered randomly - they could not tell them apart at all." In fact, this seems to conflate two different experiments. Telling letters apart was the first task in the 2004 paper, and the Arabic readers' error rates for similar letters were only 8% (Table 6) - worse than with the left hemisphere, but not nearly so bad. The claim that "there is a specific RH deficit in reading Arabic, because that is the only condition (with bilateral presentation), where these native Arabic speakers responded at chance" comes from the 2009 paper - but the task referred to there was substantially more complicated. They were looking at words/nonwords, not letters; they were presented with two words, one for each hemisphere, one of which was underlined; and they had to decide whether the underlined "word" was a real word or not. Other issues are not so much wrong as stupid: talking as though students could choose which hemisphere to learn with, for example.
However, the BBC cannot be blamed for drawing excessively sweeping conclusions from this experiment. The authors themselves talk of their results as applicable to Arabic in general, which rather overstates the case. In both papers, the Arabic speakers were all also fluent speakers of Hebrew, which they had studied since second grade, and were living in a state where Hebrew is the dominant language. In the 2004 test, at least, they were also all undergraduates studying degrees taught in Hebrew. Obviously, this is a rather unusual situation for Arabic speakers! In particular, it is one where pragmatic (and status-related) motivations to study Hebrew, and opportunities to familiarise oneself with it, are likely to be much greater than for Arabic (especially given the big difference between spoken and written Arabic.) In some types of tests, these speakers's right hemispheres seem to read Hebrew more easily than Arabic. The authors take this to mean that there is a "specific difficulty of the RH with Arabic orthography". But, without further testing elsewhere, it can equally well be taken to reflect the sociolinguistic situation of Palestinian citizens of Israel. This is, in fact, a special case of a much wider problem: most psychology experiments focus on "WEIRD" populations (read the link - it's a concept very much worth remembering when you read the science news.)