The three aforementioned research types are used commonly to measure age related psychological change, Heynes (19995) Hertzog (2003) Hofer et. al (2002) and Little et. Al (1999) all identified the choice of modelling technique and the meticulous application to obtain a true result. Reliability, validity and cohort affects also apparent.
When looking specifically at age related psychological change we can relate/ discuss complexities of the participant. That is, referring to older people, for example over 65 years. Evidence suggests that majority of older people with suspected psychological problems do not seek or receive adequate mental health service. (Lazarus, Sadavoy and Langsley 1991) describe the one of the many barriers in assessment of psychological change is older people, in their current cohort may have beliefs such as depression/anxiety are expected in old age and should be "put up with" Once these barriers are overcome the individual may then finally be able to be evaluated there are other problems that affect assessment, notably sensory and physical declines and medication affects. Vision problems plague many older adults, as can hearing decline. Stamina and information processing, as typically, with age due to changes in heart functioning, circulation. Information processing/reaction times are slowed, especially in test situations where anxiety and fatigue become problems. Health/medical illnesses and medication, commonly used by older adults can also impact on results of tests. Again relating to the empty variable issue of age. Ideally, assessments of age related psychological change would have baseline test data from earlier years which current performance could be compared. This is unfortunately not often available so the psychologist administering the assessment has to estimate abilities taking into account socioeconomic status, education, occupational history, family etc. Human judgement often is a systematic bias that can lead to inaccurate results. (Kareken 1997) This bias/inconsistency was also discussed as a major factor of concern for Hertzog (2003) and conversely, the over-compensation for this humanistic bias also leads to inaccurate results (Little et al 1999).
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Hertzog, C., Nesselroade, J.R. (2003) Assessing psychological change in adulthood: an overview of methodological issues. Psychology and aging 18 (4) 639-657`````