What is are Exogenous Zeitgebers?

External cues which regulate our internal body clock, in order to remain in time with the environment's fluctuating rhythm.

What is Entrainment?

The process of resetting the biological clock using exogenous zeitgebers.

What are the 3 main examples of Exogenous Zeitgebers?

Light

Social Cues

Temperature

How can Light reset rhythms through the body?

Can reset the SCN which is the body's main endogenous pacemaker. Can also reset other oscillators throughout the body because the protein cryptochrome (part of the protein clock) is light sensitive.

Name a Psychologist who investigated the role of Light as an Exogenous Zeitgeber?

(Initials: C&M)

Campbell & Murphy

How did Campbell and Murphy investigate the role of Light as an Exogenous Zeitgeber?

Found that if you shine light on the back of participants' knees, this reset their circadian rhythms.

Give examples of Social Cues as Exogenous Zeitgebers?

Eating at socially determined mealtimes and going to bed/waking up at times designated as appropriate for our age and lifestyles.

Name a Psychologist who investigated the role of Social Cues as an Exogenous Zeitgeber?

(Initials: D)

Davidson

How did Davidson investigate the role of Social Cues as an Exogenous Zeitgeber?

Suggested that the zeitgeber for cells such as the liver and heart is likely to be mealtimes as these cells are reset by eating.

How does Temperature regulate the life-styles of cold-blooded animals?

Cold temperature signals a time for reduced activity  and warm temperature signals the time for activity. 

Name a Psychologist who investigated the role of Temperature as an Exogenous Zeitgeber?

(Initials: B)

Buhr et al.

How did Buhr et al. investigate the role of Temperature as an Exogenous Zeitgeber?

Suggested that in warm-blooded animals, the daily changes in body temperature are governed by their own circadian clock and these temperature changes then reset other circadian rhythms.

Name 2 Psychologists supporting the role of Exogenous Zeitgebers?

(Initials: B, S)

Boivin et al.

Stevens

Why does Boivin et al. support the role of Exogenous Zeitgebers?

Male participants split into 4 groups and kept on inverted sleep-wake cycles (ie. awake at night). Each group was exposed to different light intensities and findings showed that the group with the brightest light intensity had advanced hours earlier than the other groups. This supports the effectiveness of Light as an Exogenous Zeitgeber

Describe one criticism of Boivin et al.'s study?

Lab experiment so good because variables were all controlled but bad because of ecological validity.

Name the Psychologist who countered the criticism of Boivin et al.'s light study?

(Initials: B&J)

Boivin & James

How did Boivin & James counter the criticism of Boivin et al.'s light study as lacking ecological validity?

Used intermittent bright lights in a field study of nurses which confirmed the effectiveness of light in resetting rhythms. Counters the criticism because it works in the real world and not just in lab experiments.

Why does Stevens support the role of Exogenous Zeitgebers?

Suggested that exposure to artificial lighting disrupts lighting and so disrupts melatonin production. Explains why some women in industrialised societies are more likely to develop breast cancer.

Describe Real World Application of the use of Light in treating S.A.D?

Use of Light as an Exogenous Zeitgeber to reset rhythms has developed an effective therapy known as Phototherapy to treat SAD. Uses strong lights in the morning or evening in order to change levels of seretonin/melatonin. SAD sufferers have reported the effectiveness of this therapy.

Describe a criticism of Phototherapy?

May simply be due to a placebo effect (belief that the therapy will work).