Terrace and colleagues investigated whether a chimpanzee could learn human language. A young chimpanzee, named Nim Chimpsky, was raised in human surroundings and taught signs from American Sign Language, with the aim of seeing whether he could combine signs into sentences as children do. Over several years, Nim learned to produce many individual signs and to make short sign combinations to request things. However, when Terrace analysed video recordings carefully, he found that Nim's combinations were mostly short, repetitive, and prompted by or imitated from his teachers, rather than showing the creative, rule-governed structure of children's language. The project also faced practical difficulties, including frequent changes of caregiver and questions about Nim's care once the study ended. Terrace concluded that Nim had not acquired language in the way children do, and that earlier claims about ape language may have over-interpreted the animals' productions.

References: Terrace, H. S., Petitto, L. A., Sanders, R. J. and Bever, T. G., 1979. 'Can an ape create a sentence?' Science, 206(4421), pp. 891 to 902. source adapted.

Raine, Buchsbaum and LaCasse investigated whether the brains of murderers differ from those of other people. Using positron emission tomography (PET), which measures brain activity, they scanned 41 people who had been charged with murder and had pleaded not guilty by reason of insanity, while the participants performed an attention task. Their brain activity was compared with that of a matched control group of 41 people without such a history. The murderers' group showed lower activity in some brain areas associated with controlling impulses and emotion, such as the prefrontal cortex, along with differences in other regions. The researchers were careful to state that the findings did not show that brain differences cause violence, nor that violence is beyond a person's control, but that there was an association between certain brain patterns and this group. They concluded that brain dysfunction may be one factor, among many, linked to violent behaviour.

References: Raine, A., Buchsbaum, M. and LaCasse, L., 1997. 'Brain abnormalities in murderers indicated by positron emission tomography.' Biological Psychiatry, 42(6), pp. 495 to 508. source adapted.

Loftus and Pickrell investigated whether people could be led to remember an event that never happened. Twenty-four adult participants were given short written accounts of four childhood events supposedly provided by a family member. Three of the events were true, but one, being lost in a shopping mall as a young child, was false and had been constructed with the help of a relative. Over two interviews, participants were asked to recall as much as they could about each event. About a quarter of participants came to 'remember' the false lost-in-the-mall event, sometimes adding their own details, and rated it as feeling real, although usually as slightly less vivid than the true memories. When finally told that one of the memories was false, some participants were surprised and could not identify which one. The researchers concluded that it is possible to create false memories of whole events through suggestion, with implications for the reliability of recovered memories.

References: Loftus, E. F. and Pickrell, J. E., 1995. 'The formation of false memories.' Psychiatric Annals, 25(12), pp. 720 to 725. source adapted.

Piliavin, Rodin and Piliavin investigated what affects whether people help a stranger in a real emergency. In a field experiment on a New York subway, a member of the research team staged a collapse shortly after the train left a station, falling to the floor in front of passengers. The 'victim' appeared either ill, carrying a cane, or drunk, smelling of alcohol and carrying a bottle. Observers recorded whether, how quickly, and who helped. Passengers did not know they were taking part in a study. The ill victim was helped quickly and often, usually within seconds, while the drunk victim was helped less often and after longer delays. Help was common overall, and the presence of more bystanders did not reduce helping in this real setting as much as laboratory studies had suggested. The researchers concluded that the type of victim and the costs of helping shape bystander behaviour in real emergencies.

References: Piliavin, I. M., Rodin, J. and Piliavin, J. A., 1969. 'Good Samaritanism: an underground phenomenon?' Journal of Personality and Social Psychology, 13(4), pp. 289 to 299. source adapted.

Caspi and colleagues investigated why stressful experiences lead to depression in some people but not others, focusing on a gene involved in the serotonin system. As part of a long-term study of a birth cohort in New Zealand, participants were grouped according to which version of the 5-HTT gene they carried: two short alleles, one short and one long, or two long. The researchers also measured the number of stressful life events each person had experienced in early adulthood and assessed depression. Stressful events predicted depression much more strongly in people carrying one or two short alleles than in those with two long alleles, who appeared more resilient to stress. Carrying the gene variant alone, without stress, did not strongly predict depression. The researchers concluded that genes and environment interact, so that a genetic variation moderates how strongly life stress leads to depression.

References: Caspi, A., Sugden, K., Moffitt, T. E. et al., 2003. 'Influence of life stress on depression: moderation by a polymorphism in the 5-HTT gene.' Science, 301(5631), pp. 386 to 389. source adapted.