Biological Methods

Question 1

describe ct scans?

Answer 1

In CT scanning, an x-ray is used to get the picture along with a computer which creates detailed images, (in PET scanning it is a radioactive tracer, in MRI, magnetic imaging is used). A CT scan produces pictures in slices which can be looked at individually or can be put together to give a 3-dimensional view of the “whole” area, such as part of the body. The pictures are formed and pick up how the area being scanned reacts to the x-ray being passed through it, showing how far the x-ray is blocked. Knowing how areas block the x-ray shows something about the area, such as whether a tumour is present. In psychology CT scans can be used to understand damage to the brain.

The person lies inside a large doughnut shaped scanner and the scanner is slowly rotated around them. Images of the brain and/or body are taken from different angles. It can take a few minutes to 30 minutes.

Betts (2009) did a review of the use of scanning in defence of people pleading not guilty by reason of insanity (NGRI) in courts. She mentions the use of CT, PET, MRI and fMRI scanning to provide neurological data to support claims of NCRI. Betts argues that neurological evidence does not show that a mental deficit will stop someone from knowing that what they are doing is wrong and juries may be affected by scientific evidence from scanning that suggests a cause-and-effect relationship when there is not one.

She cites the case of Herbert Weinstein, a 64-year-old man who in 1991 strangled his wife after an argument. His defence was that a cyst had caused pressure on his prefrontal cortex, which had affected his understanding of right and wrong. There was CAT scan evidence of differences in his brain (widening suici) that related to those with schizophrenia. After a long argument, the evidence was admitted, and he was acquitted but admitted to a hospital.

Question 2

strengths of ct scans?

Answer 2

• A CT scan is not painful at all and is non-invasive, which means there is no need to “enter” the body so is more psychologically ethical and may cause less distress than other methods of studying the brain, (although if a dye is used, that is not entirely the case).
• CT scanning use of X-rays which means that it is less harmful than PET scans when used in psychological research, which uses a radioactive tracer which could potentially ethically harm the patient if used to regularly.

Question 3

2 weaknesses of ct scans

Answer 3

• CAT scans require more radiation than x-rays, the more detailed the scans the more the radiation, - to they cannot be used often in psychological research as they ethically could hard participants.
• CAT scans only provide structural information, unlike PET scans which give activity information, so they have a limited use in researching links between the brain are areas of behaviour like aggression.

Question 4

describe pet scans

Answer 4

A PET scan is used to study the brain, it highlights “hot spot” areas in the brain (metabolic activity – areas most active) which tells us which parts of the brain are working at certain times. A computer generates images from the information and a radioactive tracer is added to oxygen or glucose – something that the body uses. As the tracer is used on the brain, this will show up as an area of activity. The tracer reaches the brain about 1 minute after being injected and takes 10-15 minutes to decay. As the tracer decays it releases minute amounts of radioactivity (initially in the forms of positions). The emission of radioactive particles is detected by the scanner and used to produce a record of the levels of activity in the brain tissue. This shows up as an image which can then be interpreted – the most active areas are coloured red or yellow and least active blue.

The participant is generally scanned several times in two conditions, condition one is a set of recordings taken when they are inactive, a baseline measures and condition two is another set of records taken when they are performing a task. The difference between the scans tells us which parts of the brain are involved in that activity. Language involves a number of brain areas because the individual has to find the word, prepare to speak it and then say it. By asking someone to think of words, real words, speak words and other such tasks, researchers can find which parts of the brain works for a particular language function.
PET scanning can show size of brain areas and they can then be measured and compared between people, for example, Raine et al used PET scanning to measure the prefrontal cortex levels of murders and non-murderers.

Question 5

strengths of pet scans

Answer 5

• PET scans are functional and more useful to psychologists than structural scans because they allow us to visualise events that are actually happening in the brain ie, by asking someone to think of words and detecting which parts of the brain are working. Maguire (1997) used PET scans to show that the hippocampus was active during recall of journeys by taxi drivers. This adds to the validity of the PET scans as a method.
• PET scans have been used successfully to add depth to memory research, for example, Piolino et al (2005) asked participants to recall relatively recent memories and some from long ago; their PET scans revealed that although there was some overlap in the brain areas activated, the older memories also triggered activity in some different locations in the brain.

Question 6

weaknesses of pet scans

Answer 6

• Scanners restrict movement so brain activity can only be studied in passive bodily states eg, listening or imagining, real action and moving around is limited so validity is not complete when applying to areas in psychology such as aggressive acts.
• Exposure to scanning may need to be limited because of exposure to radioactivity (tracer) which could cause health problems and is ethically not acceptable in many psychology studies.

Question 7

describe mri scans

Answer 7

Uses radio ways to measure blood oxygen levels in the brain. Those area of the brain that are most active use most oxygen and therefore blood is directed to the active area – called haemodynamic response. The activity/response is picked up through radio signals and these signals produce a series of images of successive “slices” which hare hen turned into a 3D image by a computer.
Pardini et al used fMRI scans to measure the volume of participants amygdala’s and relate this to observe levels of aggression.

Question 8

strengths of mri scans

Answer 8

• As with PET scans are accurate in checking for psychological abnormalities in the brain and the rest of the body, therefore there is validity because what is found by the scan is then often found in reality.
• Unlike PET scans which involves the use of a radioactive tracer, fMRI does not use radiation and so it is ethically a very safe method of studying the brain.

Question 9

weaknesses of mri scans

Answer 9

• Scanners restrict movement so brain activity can only be studied in passive bodily state, so physical activity is not measured at all; this means that knowledge of psychology is limited to areas like soft tissue and body organs.
• MRI scanners are noisy so could be distressing and ethically can be stressful, especially for young children who might become very distressed.

Question 10

describe one twin study

Answer 10

One twin study and one adoption study, e.g. Gottesman and Shields (1966); Ludeke et al. (2013).

Twin and adoption studies are used to study the influence of GENES on behaviour. Genes and DNA give the biological blueprint for each person’s development; they interact with the environment as the person grows.

Identical twins have identical genes; non-identical twins share 50% of their genes. By comparing identical and non-identical twins with regard to a certain characteristic, it can be seen what influence genes have. A problem is that twins share much of their environment as well as their gene, which is why adoption is important.

Adopted children are brought up in different families and do not share their environment with their biological family. Identical twins that are reared apart, not sharing the same environment but sharing the same genes, are important as participants as that too controls the effects of environment, to an extent at least.
Twin and adoption studies relate to the nature-nurture debate, which is about how far a characteristic comes from nature and how far it comes from nurture.

Nature is what we are born with and is controlled by our genes. Nurture is what we experience from the environment as we develop. Environment includes influence from parents, culture, interactions with others and all other experiences.

TWIN STUDIES
Identical (mz, monozygotic) twins share 100% of their genes because they come from one egg fertilised by one sperm. Studies with mz twins are slightly different from correlational studies because instead of comparing two variables from one person, the identical twins are compared with one another. Dizygotic (DZ) twins are non-identical which means that they come from 2 fertilised eggs (Di= two). Since they develop from different eggs, the DNA of DZ twins is only as similar as that of any siblings, it is not 100% the same, as it is in identical twins.
A concordance rate is established when a correlational statistical test is carried out comparing how one twin scores on a variable of interest compared with the other twin, for example, IQ is studied in this way. The IQ score from one identical twin can be set against the IQ score for the other identical twin; thus we can see whether one has a high IQ score when the other does too. If this is the case, there would seem to be grounds for saying that IQ is, at least to an extent, genetic in origin. Characteristics which are studied in this way include schizophrenia, IQ, alcoholism, depression, personality and anorexia.

Question 11

describe strengths of a twin study

Answer 11

• twins provide a more valid comparison of shared genetic information than studies of siblings, as twins are the same age so are not subject to cohort effects so they are in effect their own control.
• twin studies suggest that genetic components may be involved in a wide range of psychological areas for example, Heterena et al (2003) found that MZ twins were more similar than DZ twins in their tendency to become classically conditioned to fearful stimuli as snakes and spiders.
• Twin studies have generated a large volume of data covering a wide variety of psychological variables for example Gottesman found a 48% concordance rate for MZ twins in relation to schizophrenia than 17% of DZ twins.

Question 12

weaknesses of twin studies

Answer 12

• MZ twins look alike and so are likely to be treated in exactly the same way by other people, creating a more similar environment for MZ twins than DZ twins, therefore we do not know if it is due to genes (nature) or environment (nurture).
• As most people are not twins, the results from twin studies may not be representative or therefore generalisable to the entire population.
• In addition it is difficult to find large numbers of twins therefore sample sizes are likely to be small so again generalisability is limited.

Question 13

describe brendgen study

Answer 13

Picture
BRENDGEN ET AL.’S STUDY
APRC
Aim

To find out if there is a difference between physical and social aggression in 6-year-old school children by surveying their teachers and classmates. In particular, to see if physically aggressive children are also socially aggressive and to investigate whether the link is down to genetics or social situation by comparing MZ and DZ twins.
There are other studies into the origins of aggression. Bandura’s Bobo Doll studies look at how children learn aggression from the environment and Raine et al. look at how aggression is linked to brain deficits (but may have environmental explanations too)
IV

As a twin study, this looks for a correlation between (1) the aggression scores for identical (MZ) twins and (2) the aggression scores for non-identical (DZ) twins.

It also examines the correlation between (3) teacher ratings for the children’s aggression and (4) peer ratings from classmates for the children’s aggression.

As a natural experiment, it looks at the differences between (5) MZ and DZ twins and (6) girls and boys

DV

Teacher ratings for social and physical aggression were calculated out of 6 each; Peer ratings were taken from classmates who were asked to identify classmates from photographs who fitted various descriptions.
A main advantage of the present study is it assessed behavior not only by teachers but also by peers, who are rarely employed as a reporting source in twin studies - Mara Brendgen
The teacher overall scores for each child take the form of interval/ratio level data, but the children’s responses are frequencies for each child that take the form of nominal level data.

Sample

234 pairs of twins, taken from the Quebec Newborn Twin Study. This was a longitudinal study that was already going on and Brendgen used the data from it when the children were age 6.

There were 44 sets of identical (MZ) male twins, 50 sets of identical (MZ) female twins, 41 non-identical (DZ) males, 32 non-identical (DZ) females and 67 sets of non-identical (DZ) mixed-gender twins.

Because the sample was taken from another study, this should be considered a cluster sample.
Picture
Procedure

The children had been entered into the Quebec Newborn Twin Study when they were born. They were assigned to MZ or DZ based on physical resemblance; 123 pairs of twins were DNA-tested and this backed up the assignment to MZ or DZ 94% of the time, which was considered reliable enough.

By age 6, 88 pairs of twins had dropped out of the study, but Brendgen obtained data on the remaining 234 twin pairs, got written consent from the parents and approached their schools. Because this was Quebec, some of the schools were English-speaking and some were French-speaking, so they surveys had to be translated and the researchers had to speak both languages.

The teachers’ questionnaires asked them to rate each child on a 3-point scale (0 = never, 1 = sometimes, 2 = often) on these 6 statements:
tries to make others dislike a child
says bad things or spreads nasty rumors about another child
becomes friends with another child for revenge
gets into fights
physically attacks others
hits, bites or kicks others

The scores for social aggression and physical aggression were added together to produce two overall scores.

For the peer ratings, the children were given a simpler task. They were shown photos of their classmates and asked to circle the photos of 3 children who best fit these 4 descriptions:
tells others not to play with a child
tells mean secrets about another child
gets into fights
hits, bites or kicks others

Question 14

strenfths of brendgen study

Answer 14

• Adoption studies allow the identification of interesting relationships being linked to genetics and these can then be investigated further, eg, IQ, aggression etc.
• Adoption studies directly compare the influence of genes versus the environment so has good face validity because they isolate the influences of the environment due to the effects of the adoptive parents during the adopted individual’s childhood.
• Some studies can be longitudinal therefore they can be studied for differences over a longer period of time so more trends can be identified and extensive conclusions made on factors like IQ, aggression and schizophrenia.

Question 15

weakness of brendgen study

Answer 15

• Selective placements mean that frequently people are placed with families very similar to their biological families, this makes untangling the influences of genes and environment very difficult.
• The samples are not representative, most people are not adopted, hence by definition people who are adopted are not representative of the whole population
• Families that adopt are similar to each other, so it may be something in that similarity of families who adopt that is causing the results, ie, specific types of family trait like more empathy or a need for financial reward.

Question 16

describe heston adoption study

Answer 16

Heston’s (1966) study aimed to test this assumption through an adoption study which separated nature from nurture.
Procedure
The participants in the study were born between 1915 – 1945 to schizophrenic mothers in an American psychiatric hospital (where most were born in the hospital). Children were selected if their mothers had put them up for adoption and the researchers ensured the mother had (a) a diagnosis of schizophrenia; (b) evidence of behaviour consistent with schizophrenia; (c) no diseases; (d) that the child and mother were separated from birth. 74 children satisfied the conditions and it was checked that the child had no contact with the mother or her family from birth. The father’s psychiatric status was not checked but none were known to be hospital patients.
Sixteen participants were dropped for reasons including death, contact with mother, disease, and no control participant due to exceptional circumstances, which left 58 participants. The remaining 58 participants were matched with like controls on sex, type of eventual placement, and length of time in child care. Due to further deaths and loss of contact through follow-up there were 47 experimental participants (30 male, 17 female) and 50 controls (33 male, 17 female).
To assess psychiatric status at follow-up the following were used where possible: Police records; Retail credit reports; School records; Civil and criminal court actions; Newspaper files were reviewed; Any psychiatric hospital records; Relatives, friends and employers were contacted; Personal interview (25/97 either refused or were not available); Minnesota Multiphasic Personality Inventory (MMPI); IQ score (either from school/other records) or an IQ test was conducted. Social class of the participant’s first home; Participant’s current social class
Two psychiatrists evaluated the dossier compiled on each participant blindly and independently. A third evaluation was made by Heston himself. A diagnosis of schizophrenia was given only when all three raters agreed and they were also diagnosed by a psychiatric hospital. A score of 1-100 was assigned to each participant regarding this psycho-social disability (where 100 was highest) where scores below 75 indicate psychiatric symptoms become troublesome.
A summary of the findings/results is below:

As a result, Heston (1966) concluded that the findings support the influence of genes in schizophrenia, and that inheritance also contributes to psycho-social disability.
There must be other possible factors influencing the development of schizophrenia though because Heston also reports that half of the participants born to the schizophrenic mothers were successful adults who possessed artistic talents and imaginative adaptations to life which was not found in the control group.

Question 17

strengths of heston study

Answer 17

Advantages
Inter-rater reliability makes the study valid.
Two groups were matched which makes the study consider individual differences.
All children were adopted at birth which means that there were no confounding variables, making the study more valid.

Question 18

weaknesses of heston adoption study

Answer 18

Disadvantages
All American participants makes the study less generalisable.
Most people are not adopted which makes the study less representative.
Children normally go to similar families which means that there are confounding variables affecting the validity.

Question 19

describe positive, negative correlations

Answer 19

Correlational designs involve comparing data from the same participants or two sets of data. Two measures are taken from one individual and recorded. Once enough scores are obtained from participants the relationship between the scores are rested.
There are three types of correlations (relationships),
1. Positive Correlation is when one score rises as the other rises – for example, as age increases so does the time it takes to react to a stimulus.
2. Negative Correlation is when one scores rises as the other falls – for example, as age rises, average driving speed falls.
3. Zero Correlations is when there is no relationship between the variables.
Features of Correlations,
- There is no IV or DV, there are variables of equal importance.
- The hypothesis will not be about difference it will be about a relationship between two variables.
- The hypothesis could be directional because it could predict a positive or negative correlation
- A scatter diagram will show whether a correlation is positive, negative or neither.
- Correlations involve sampling - random, stratified, opportunity and volunteer.
- Correlations do not involve randomising to groups, the sample is scored for both the variables, and so there is no need to sort out which participant goes in which group.

Question 20

strengths of correlational research

Answer 20

• Initial relationships can be discovered which might not have been realised prior because a flexible design like correlations can lead to new variable relationships.
• The same people are providing both sets of data, so the data will not be affected by individual differences – therefore the results are not affected by participant variables.

Question 21

weaknesses of correlational research

Answer 21

• Correlational designs only indicate a relationship between two variables there is not cause and effect, there could be other variables influencing the behaviour.
• The measures might not provide valid data, time in therapy is a clear measure but the benefits of therapy are not easy to quantify. Some variables are more valid than others, (but a correlation can use data from unnatural measures).

Question 22

describe scatter diagrams

Answer 22

Correlation data can be displayed using a scatter diagram. A scatter diagram is also referred to as a scattergraph or scattergram. The two scores from each participant or variable generate a point on the graph, so in our example there are ten points. A LINE OF BEST FIT is drawn – if there is a relationship, the line of best fit is close to most of the points.
Drawing a scatter diagram displays data in a way that suggests, using a best line of fit, whether the data has relationship between the two variables or not. A line of best fit is drawn that shows the best straight line that can be fitted with the points on the scatter diagram evenly distributed either side of the line. The line is diagonal, either from left to right from top to bottom, or from left to right from top to bottom. The lines should run left to right. If it is not clear which way they line should go (top to bottom or left to right) this suggests there is no relationship. If plots are “scattered” all over the graph, then no relationship was found.
* Positive Correlations: if one line rises from left to right on the scatter diagram, then that shows a positive relationship – as one score rises, the other rises too.
* Negative Correlation: if the line falls from left to right on the scatter diagram, then that shows a negative relationship – as one score rises, the other falls.
* No correlation: if scores do not cluster well either side of the line of best fit, then the graph suggests that there is no relationship between the variables.
Correlations can be said to be ”strong” if the plots are close to the line of best fit with a few scores not so close. They are “weak” if they cluster around a line of best fit but only rather loosely. They can have “medium” strength too.
A scatter diagram can suggest:
- Whether there is a correlation or not
- Whether, if there is none, a correlation is negative or positive
- How strong the correlation is.
Draw and label (with best line of fit) a scatter diagram/graph

Summarise what the graph shows

Summary
The line of fit, with five scores on each side, is in a positive direction. The three scores that do not fit well are clearly shown on this graph. Overall, this graph suggests that there is a positive correlation between time having therapy and improvements in aggression score.

A statistical test (Spearman rank correlation coefficient) can be carried out to see if the relationship is real for the group as a whole:
- If both scores rise, there is a positive correlation. A result of +1 means a perfect correlation, there is a perfect relationship between the two sores.
- A result of 0 means there is no correlation. The two scores do not relate to each other.
- If one score rises and the other falls, there is a negative correlation. A result of -1 means a perfect negative correlation. So there is a perfect relationship between the two sores.
- The closer a correlation is (the result of the test) to 1 (either negative or positive), the “better” the correlation is (1 is a perfect correlation).
For example, a test result of +0.7 or higher shows a positive relationship, a test result of -0.7 or lower shows a negative relationship. That is not to say that a result of +0.45 does not show a relationship, but when a result is close to 0, it would seem there is no correlation.

Question 23

what is the 2 criteria for spearmans rank correlation coefficient

Answer 23

2 criteria
- Looking for a relationship (no difference)
- Data at least ordinal (interval/ratio as well)

Question 24

describe the levels of measurement

Answer 24

Numerical data can be classified into FOUR different levels of measurement,
NOMINAL data is when totals are counted in two or more named, discrete categories. This means that the categories are unrelated – they do not lie on a linear scale. Asking someone to give a YES or No answer to a question produces nominal data as would a closed question about prejudice such as “would you laugh at a sexist joke?”. We can classify people as either right or left handed or describe their personality as anal, oral or phallic, we are putting them into nominal categories. As you can see, it is possible to have more than two categories.

ORDINAL data is represented on a linear scale such as a rating or “points” system. There is a clear increase in the value of points along the scale but the divisions between those points are not necessarily equal; for example, if we ask participants to rate their night’s sleep as very poor, disturbed, somewhat interrupted, fair or very good, we could be sure that someone who answered “very good” had a better night’s sleep than a person who rated their sleep as “fair”. We could not however, be sure that the “gap” between “very good” was the same as the gap between “fair” and “somewhat interrupted”. In an ordinal scale, numbers may be allocated to points on a scale for example, the rating of sleep could be replaced with “Rate your night’s sleep from 1 to 5 (1 is the best)”. Even though this is now a numerical scale, we still don’t know if the difference between the ratings 1 and 2 is the same as between 2 and 3.

INTERVAL data, like ordinal, the points lie on a scale but here the gaps between the points are equal. If we ask participants to remember nonsense trigrams (like XKN) in a recall test, each one is equally memorable. The same may be true for some words, but not all. For example, it is likely that dog, ant, pig, hen, fox and cat are all equally easy to remember – they are all short, familiar animal names that are one syllable long. However if the list included, giraffe, hippopotamus and tyrannosaurus, it is unlikely that each item would be worth the same amount in terms of what it indicates about the participant’s memory. This may be because some are longer than others, or more distinctive. In this case we could not say that the level of measurement was interval. Commonly used interval scales include measures of IQ and personality.

RATIO data, like interval data has equal intervals between the points. The difference between the two is that on a ratio scale there is a true zero. This doesn’t mean that it has to be possible for a participant to score zero. Simply that the baseline measurement begins at nought/ “0”. Imagine a study that is investigating stress, one way to measure the effects of stress would be to measure pulse rate. Even our most relaxed participants at the start of the study would have sores considerably higher than zero, but the scale itself would be measuring from this point. To return to our example of remembering words – if someone could remember no words at all this might not mean they have no memory at all, but if a participant had a pulse rate of zero, it would mean they had no pulse at all.

Question 25

describe levels of significance

Answer 25

In psychology we learn about people and from them we create tests and results which need to be analysed. For this to be achieved we need to know if our results are sound and this is where we apply levels of significance. The statistical test will judge whether the null hypothesis which states that our results were due to CHANCE actually are. So it could not have arisen by chance, then the pattern is described as a SIGNIFICANT ONE.
WHAT IS CHANCE?
In any study there is an element within it that could cause our results to be due to something else (chance) and not the IV as we planned. We therefore need to measure to what extent CHANCE influenced our results, if in fact it did. So the idea is to decide what is down to chance and to be able to determine whether a difference or relationship is significant.

Question 26

describe correlation hypothesis

Answer 26

Correlation means association - more precisely it is a measure of the extent to which two variables are related. There are three possible results of a correlational study: a positive correlation, a negative correlation, and no correlation.
* A positive correlation is a relationship between two variables in which both variables either increase or decrease at the same time. An example would be height and weight. Taller people tend to be heavier.
* A negative correlation is a relationship between two variables in which an increase in one variable is associated with a decrease in the other. An example would be height above sea level and temperature. As you climb the mountain (increase in height) it gets colder (decrease in temperature).
* Zero correlation exists when there is no relationship between two variables. For example, there is no relationship between the amount of tea drunk and level of intelligence.

Question 27

describe experimental and null-hypothesis

Answer 27

OPERATIONALISE VARIABLES – psychologists use the term “operationalise” to describe the fact that a hypothesis is highly specific. OPERATIONALISE means spelling out the various operations. In other words you narrow the topic area down in order to measure it accurately. For example, the concept of a young child was operationalised as “a child under the age of seven” OR a cognitive task as specified as “the conservation of volume”.
The INDEPENDENT VARIABLE is the variable which the experimenter manipulates. The DEPENDENT VARIABLE is the one which the experimenter measures. If you find this confusing, try to think of it like this, the value of the dependent variable depends on the value of the independent variable. The psychologist, when she sets up a study, thinks “if I do so- and so then such- and such will happen”. The so-and-so is the independent variable and the such-and–such is the dependent variable.

Question 28

describe ALTERNATIVE, EXPERIMENTAL AND NULL-HYPOTHESES AND ONE OR TWO TAILED WITH REGARD TO TESTS

Answer 28

Now that we have collected our data we must decide between 2 hypotheses,
1. The H (E) EXPERIMENTAL HYPOTHESIS which states that students will recall significantly more on a Monday morning than on a Friday afternoon. Any difference in the DV (recall) will be due to the IV (Friday afternoon or Monday morning) and not chance.
AND
2. The H (O) NULL HYPOTHESIS which states that there will be no significant difference in recall between Monday morning and Friday afternoon. Any significant difference in the DV (recall) will be due to chance and not the IV (Friday afternoon or Monday morning).
Just to confuse you, the experimental hypothesis is sometimes referred to as the ALTERNATIVE HYPOTHESIS. Remember that some studies are not experiments (they may be observations, interviews etc.) and in this case we do not start with an experimental hypothesis but with an alternative hypothesis. When we carry out an experiment we can use either term.
Sometimes a hypothesis PREDICTS the direction in which the results are expected to go, for example, “studying IMPROVES exam marks”, “women are BETTER drivers than men”. When a hypothesis predicts the direction of the results it is referred to as a ONE-TAILED hypothesis.
If a hypothesis does not state a direction but simply says that one factor affects another, or that there will be a difference between two sets of scores without saying in which direction the difference will be, then it is called a TWO-TAILED hypothesis. Examples of two-tailed hypotheses are “anxiety influences performance”, “there is a significant difference in the driving abilities of men and women”.
Distinguishing between one- and two-tailed hypotheses is really very straightforward but be careful! Sometimes, because we ourselves expect results to go in a certain direction, we assume a hypothesis is one-tailed when in fact it is two-tailed. For example, everyone knows the more you revise, the better you do in exams (not that I’m hinting of course!) but a hypothesis may say “studying significantly affects exam results” and this, of course, a two-tailed hypothesis and allows for the possibility that the more you study the worse will be your exam marks. SO
A ONE-TAILED HYPOTHESIS STATES THE DIRECTION IN WHICH THE RESULTS ARE EXPECTED TO GO (IE, IN ONE DIRECTION).
A TWO-TAILED HYPOTHESIS DOES NOT GIVE A PREDICTED DIRECTION.

Question 29

describe randomisation

Answer 29

Involves allocating individuals to certain groups, in the case of independent measures design, there are three ways that you can randomly allocate participants. One involves manual selection which means that all names are placed in a hat for example, and participant 1 pulled out goes to condition one, and participant 2 to condition 2. The others involve computer selection or using a random number table. Randomly allocating participants to different conditions can eliminate bias and therefore it is due to chance factors that those involved end up in the different conditions.

Question 30

describe the use of the control condition

Answer 30

Experimental investigations involve a control group, which is a baseline which the experimental condition is compared against. In the experimental condition it is influenced by the IV, the control condition is not.
However, it is important that both conditions are well matched otherwise, we cannot be sure that the influence in the experimental is actually the IV. For example, if a research was looking at the effect of music on recall, they may compare some participants who are exposed to music (EC) to others who are not (CC).
This looks controlled but it is only controlled for the absence of the IV, a better control group in this case might be exposure to white noise at the same volume as the music was played. This would control for the possible effect of interference by the volume of the sound rather than, say, the rhythm of the music or meaning of the lyrics.

Question 31

describe the biological link from theory

Answer 31

In studies on the nervous system, such as the effectiveness of drug treatments, the control is often given a “placebo”, which is a “sugar pill” or treatment that appears to be the real thing but actually has no active ingredient. The reason for this being that believing that you can get better may have an effect on recovery and by using the placebo cancels this out.

ADAMS ET AL (2005) conducted a meta-analysis of studies investigating the effectiveness of the drugs chlorpromazine in the treatment of schizophrenia. After combining findings relating to 5276 patients treated with either the drug or placebo control, they concluded that, although the drug was effective, a considerable placebo effect could also be seen. For example, relapse was prevented in 47% of patients taking chlorpromazine but 17% of those receiving a placebo also remained in remission. A similar pattern is seen in the treatment of obsessive compulsive disorders (FINEBERG ET AL 2007).