Tuesday, 30 November 2010

Gale et al (2007)

Researchers studied the relationship between vegetarianism and IQ. Mental abilities were tested age 10, and the same cohort was surveyed at age 30. It was found that vegetarians in the study were more likely to be female, and to have better academic qualifications.

IQ at age ten was found to predict later vegetarianism - those of higher IQ were more likely to become vegetarians later in life, even after taking social class into account.

Gale, C.R., Deary, I.J., Schoon, I. and Batty, G.D. (2007). IQ and vegetarianism in adulthood: 1970 British cohort study. British Medical Journal, 334(7587), 245.

Saturday, 27 November 2010

Jacobs (1887)

An early study of STM capacity

Even people who haven't studied Psychology can probably tell you about the 'magical number' 7 (plus or minus two) - the supposed maximum number of items we can hold in our short-term memories.

The best known study is Miller (1956), who tried to investigate the reason for the limit, finding that it was not limited to information load - the rationale being that a short word contains a lot more information than a binary digit (0 or 1) but yet the limit is still in the range of 5-9 items.

However the concept was known long before Miller, so it is not strictly accurate to attribute it to him.  Ebbinghaus investigated it, and in the UK, Jacobs studied what he called 'prehension'.  Participants were presented sequences of numbers, and asked to repeat them in the correct order. The sequences are initially short, and gradually increase in length one digit at a time. A person's digit span is the point at which they can recall sequences of a certain length (e.g. seven items) correctly 50% of the time. Jacobs found a digit span of 9.3 on average - when letters were used, the average was 7.3 items. Age differences were also found, with digit span increasing through childhood.

Miller was the first to talk about 'chunks' of information, but even that concept has largely been superceded by the idea of a time-limit (how many items can be pronounced in just under two seconds), leading Schweickert & Boruff (1986) to wittily question, magic number or magic spell?

Jacobs, J. (1887). Experiments in prehension. Mind, 12, 75-79.

Rummel et al (2003)

Use of Mnemonics

Rummel asked students to read a historical passage on concepts of human intelligence. They were then randomly assigned to process the passage using either mnemonics or free study techniques. Participants given mnemonics remembered more names and contributions than did the participants in the free study condition.

Rummel, N., Levin, J.R., and Woodward, M.M. (2003) Do pictorial mnemonic text-learning aids give students something worth writing about? Journal of Educational Psychology, 95(2), 327.

Tuesday, 16 November 2010

Duncan et al (2000)

Brain area for 'g factor'

The researchers found support for the concept of a single ‘g’ factor. The study used PET brain scans while participants completed cognitive tasks. The tasks were diverse, some had a ‘high g’ problem solving nature, and others didn’t. A brain area called lateral pre-frontal cortex was active for all of the high g tasks, even though tasks varied widely. This area was not active for ‘low g’ tasks.

Duncan, J., Seitz, R.J., Kolodny, J., Bor, D., Herzog, H., Ahmed, A., Newell, F.N. and Emslie, H. (2000). A neural basis for intelligence. Science, 289, 457-459.

Spearman (1904)

The 'g' factor  

Sir Charles Spearman used a statistical technique called ‘factor analysis’ to determine how many underlying factors influenced children’s scores on tests. Spearman developed some simplistic tests, such as vocabulary, visualisation, mathematics ability, ability to match colours, ability to match musical tones, and ability to follow complex instructions.

 He administered these to small samples of (primary age) school children. He found that children tended to fall on the same rank order on all tests, for example, excel in all, or gain below-average scores on all tests. Using factor analysis, Spearman found a single factor underlying all of these performances, which he termed the ‘g’ factor or General Intelligence.  Variations among one child's abilities was described as the product of a 'specific factor'.

The idea of a general intelligence level is now widely accepted in society, and the concept of the ‘g’ factor is still influential in psychology. It should be noted that Spearman’s sample was small, and the tasks used were quite simplistic and limited. Rather than general intelligence, the common factor could reflect some other feature such as motivation or language ability. In addition, other researchers have used similar methods but found a larger number of factors (such as Thurstone’s 7 ‘Primary Mental Abilities’).

The statistical result of this study was not really strong enough evidence for Spearman and his followers to claim that 'g' is fixed and innate, as was widely assumed following this work (see Gould, 1982).  Furthermore, even if general intelligence is as Spearman described, it includes only a limited range of human traits, and most psychologists nowadays see intelligence more broadly - often including social and creative abilities.


Spearman, C. (1904). ‘General intelligence’, objectively determined and measured. American Journal of Psychology, 15, 201-293.

See also: Gardner's theory of multiple intelligences

Friday, 12 November 2010

Sperling (1960)

The capacity of sensory memory

Sensory memory consists of the brief representation of information which hits our senses. It fades within a second or two if we do not pay attention to and process the information.

Because participants can recall very little from presentations to the sensory memory, it could be assumed that these stores have a small capacity. However, Sperling used tones to cue participants to recall only part of the presentation. Using this method, recall from a 12-item grid of letters rose to 75%.

It can therefore be concluded that sensory memory has a large capacity, but most items fade before they can be processed.

Sperling, G. (1960). The information available from brief visual presentations, Psychological Monographs, 74 (whole no. 498), 1-29.

Tuesday, 9 November 2010

Rutter (1998)

Developmental Catch-up

Michael Rutter, a major critic of Bowlby's theory of maternal deprivation, studied the level of improvement in cognitive functioning among Romanian orphans adopted in the UK. 111 children were studied, and they joined their adoptive families aged 2 or younger after severe privation in their home country.

Measures were taken at age 4, including IQ and language tests. A control group of UK adoptees was also used. It was found that the Romanian children had effectively caught up with the UK control group, as their test scores were only slightly lower.

It was concluded that with the right care and an enriched environment, early privation can be overcome. A criticism of the study is that functioning at age 2 was based on adoptive parents' recollections.

Rutter, M. and the ERA study team (1998). Developmental catch-up, and deficit, following adoption aftere severe global early privation. Journal of Child Psychiatry, 39(4), 465-476.

Tuesday, 2 November 2010

Wilson (2001)

Stress and multimedia
The researcher used stress responses to investigate multimedia quality, and compared then with subjective assessment by questionnaire. It was found that poorer quality video and audio do result in stress symptoms, and that these don’t always correlate with questionnaire reports of stress or inconvenience.
Wilson, G.M. (2001). Psychophysiological indicators of the impact of media quality on users. CHI 2001: Extended Abstracts on Human Factors in Computing Systems, 95 – 96.