The Handbook of Intellectual Disability and Clinical Psychology Practice
Total Page:16
File Type:pdf, Size:1020Kb
This article was downloaded by: 10.3.98.104 On: 26 Sep 2021 Access details: subscription number Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: 5 Howick Place, London SW1P 1WG, UK The Handbook of Intellectual Disability and Clinical Psychology Practice Alan Carr, Christine Linehan, Gary O’Reilly, Patricia Noonan Walsh, John McEvoy Intelligence Publication details https://www.routledgehandbooks.com/doi/10.4324/9781315739229.ch3 Gary O’Reilly, Alan Carr Published online on: 20 Apr 2016 How to cite :- Gary O’Reilly, Alan Carr. 20 Apr 2016, Intelligence from: The Handbook of Intellectual Disability and Clinical Psychology Practice Routledge Accessed on: 26 Sep 2021 https://www.routledgehandbooks.com/doi/10.4324/9781315739229.ch3 PLEASE SCROLL DOWN FOR DOCUMENT Full terms and conditions of use: https://www.routledgehandbooks.com/legal-notices/terms This Document PDF may be used for research, teaching and private study purposes. Any substantial or systematic reproductions, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The publisher shall not be liable for an loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material. Section 2 Assessment frameworks Downloaded By: 10.3.98.104 At: 15:44 26 Sep 2021; For: 9781315739229, chapter3, 10.4324/9781315739229.ch3 This page intentionally left blank Downloaded By: 10.3.98.104 At: 15:44 26 Sep 2021; For: 9781315739229, chapter3, 10.4324/9781315739229.ch3 Chapter 3 Intelligence Gary O’Reilly and Alan Carr Charles Darwin noted human intelligence is not of a different kind but simply differs in degree relative to other living animals (Darwin, 1871). Darwin understood that to critically understand our intellectual ability requires us to understand its evolution. Consequently, although it may seem removed from clinical practice we begin this chapter by describing how our species evolved its intelligence over the last 7 million years. We feel this provides an understanding of our intellectual capacities and their evolutionary and cultural origins and gives us an often missing critical perspective on the most common theories and areas of research in the field of human intelligence today that are relevant to clinical practice. What is human intelligence? Although the study of human intelligence is as old as a scientific psychology we have no final consensus about its nature. From the perspective of those working with people who have an intellectual disability, arguably the most important definition of intelligence is offered by the American Association on Intellectual and Developmental Disabilities (AAIDD, 2010) who define it as follows: Intelligence is a general mental capability. It includes reasoning, planning, solving prob- lems, thinking abstractly, comprehending complex ideas, learning quickly, and learning from experience. (AAIDD, 2010, p. 15) This definition offers guidance on what should be considered the core features of intelli- gence: reasoning, planning, solving problems, thinking abstractly, comprehending com- plex ideas, learning quickly and learning from experience. The AAIDD further highlight the importance of understanding that the expression of human intelligence depends on the context of an individual’s life, their level of adaptive behaviour, their opportunities for par- ticipation in society, their interactions with others, the social roles available to them, and their health status. They also conclude that despite many limitations, the best approach to the formal assessment of intelligence currently available to us is through the appropriate use of standardised psychometric tests. This definition fits well with theories of human intelligence that draw upon the psychomet- ric approach. However, as we hope to demonstrate in this chapter, there is much more to our understanding of human intellectual abilities than that offered by the psychometric approach and the associated AAIDD definition. In this chapter we will introduce the reader to two broad theoretical approaches to understanding human intelligence. These stem from (1) human evolution and (2) the psychometric approach. We will also review relevant research Downloaded By: 10.3.98.104 At: 15:44 26 Sep 2021; For: 9781315739229, chapter3, 10.4324/9781315739229.ch3 82 Gary O’Reilly and Alan Carr linked to these approaches in the areas of genetics, the neurobiology of intelligence, and the rise in measured IQ scores since formal testing began. Models of intelligence 1. The evolution of human intelligence Human evolution Our closest primate relative is the modern chimpanzee. In evolutionary terms chimpanzees are our cousins rather than our ancestors. We last shared a common ancestor with chim- panzees somewhere between 6–7 million years ago. Figure 3.1 provides a brief review of the evolutionary history of our species and our ancestors over the last 7 million years. The account that follows is taken from Klein (2009) and Lewin and Foley (2004) unless other- wise stated. The precise identity of our last common ancestor with chimpanzees is currently not pre- cisely known, but a number of potential candidates are identified in the fossil record from 6–7 million years ago (Sahelanthropus tchadensis (Brunet et al., 2002); Orrorin tugenensis; and Ardipithecus ramidus (Lovejoy et al., 2009)). Each is roughly equivalent to the modern chimp in cranial capacity (and by implication intellectual ability) but has anatomical fea- tures suggestive of a change towards bi-pedalism that supported a lifestyle of mixed living in trees and open grassland. By 3–4 million years ago the African continental environment of our ancestors changed to one of increased woodland and open terrain. In that context a series of potential ancestors to modern humans branching from our last common ancestor with chimpanzees are identified in the fossil record who were better adapted to that environ- ment. They are variations of a group of related species classified as Australopithecines. From roughly 3–4 million years ago these include the gracile Australopithecus afarensis (Lucy) which showed no brain enlargement but were better adapted to a bi-pedal lifestyle; and from 1.5–2 million years ago the more robust Australopithecus boisei, similar in brain size and bi- pedally adapted. The latter’s main anatomical change is the emergence of larger flatter teeth specialised for chewing more fibrous and coarser foods (possibly grass, grains and leaves). So our anatomical development from 7 million to roughly 2.5 million years ago is not asso- ciated with brain and intelligence change; rather it has proceeded from ancestors adapted to a predominantly tree-dwelling lifestyle to a mixed tree–terrestrial lifestyle to an exclusively terrestrial lifestyle. Anatomically this has seen the emergence of a bi-pedal anatomy with body features that support a mixed tree–terrestrial lifestyle, ultimately adapting in favour of an exclusively bi-pedal anatomy by approximately 2 million years ago. The next phase of human development from approximately 2.5 million years ago comprises a full adaptation to bi-pedalism, coupled with brain enlargement, tool use, tool manufacture, social group change, migration from the African continent, the development of language, and symbolic representation. These anatomical and behavioural changes evidence the underlying intellec- tual capacities we developed over that period. Somewhere around 2.5 million years ago, one or possibly two species (Homo habilis and Homo rudolfensis) are identified in the fossil record that show evidence of increased cranial capacity without an increase in overall body size. They also had a more human-like precision hand grasp and, although bi-pedal, a lower body that is more ape-like than human. Homo habilis and Homo rudolfensis most likely produced simple stone tools that had a loose cogni- tive template that supported their manufacture; these were used for scraping, sawing, cutting and breaking wood, grass, meat, bone and animal hide. In reality we know nothing of their linguistic ability. However their stone tool production suggests a similar level of right-hand Downloaded By: 10.3.98.104 At: 15:44 26 Sep 2021; For: 9781315739229, chapter3, 10.4324/9781315739229.ch3 Intelligence 83 (modern man) Modern chimpanzees Homo sapiens sapiens Homo Homo Recent environment heidelbergensis specialization to neanderthalensis Homo floresiensis 500,000 years ago500,000 years Today ago migration Further brain Homo erectus 2 million years enlargement & Homo ergaster ago tool production Homo habilis 2.5 million years Homo rudolfensis brain enlargement & brain enlargement Earliest humans first ing i ew stus ago bu boise st” ch st” ro bu stralopithecus stralopithecus stralopithecus aethiopicus specialization apes with more “ro Au Au Au 1.5−2 million years Later African bi-pedal s “Lucy” canu ago garhi ri y African rl af anamensis stralopithecus stralopithecus stralopithecus stralopithecus stralopithecus bahrelghazali Ea afarensis afarensis Au Au Au Au Au 3−4 million years wooded/more open terrain bi-pedal apes r ears rn ees ago Common ancestor/ liest hominins n tugenensis ramidus ri 6−7 million y tchadensis ear with mode Ardipithecus