Early-generation computerized x-ray studies (CAT scans, CT scans) and radiographic cerebral blood-flow studies (angiograms) began to augment experimental and observational studies of aphasia in the 1970s, but they gave very crude information about where the damaged part of the brain was located. These early brain-imaging techniques could only see what parts of the brain had serious damage or restricted blood flow. They could not give information about the actual activity that was taking place in the brain, so they could not follow what was happening during language processing in normal or aphasic speakers. Studies of normal speakers in that period mostly looked at which side of the brain was most involved in processing written or spoken language, because this information could be gotten from laboratory tasks involving reading or listening under difficult conditions, such as listening to different kinds of information presented to the two ears at the same time (dichotic listening).