Learning about time

Question 1

What is time estimation?

Answer 1

We are good at estimating time periods, and making judgements about whether intervals are shorter or longer than each other

We are also sensitive to the day/night time and 24-hour cycle: waking up just before your alarm goes off and not just because of the sun

Question 2

What is periodic timing?

Answer 2

learning to respond at a particular time of day

Question 3

What is interval timing?

Answer 3

learning to respond after a particular interval of time

Question 4

How did Roberts (1965) study cockroaches?

Answer 4

Increased activity at dusk, when removed visual cues cycle drifted until increased activity started 15 hours before dusk (cycle slightly less than 24 hours)

Restoring visual cues produced a gradual shift back to correct time

Entrainment: light acts as a zeitgeber, synchronising the internal clock (resets internal clock)

Question 5

What did Bolles and Stokes (1965) say about periodic timing?

Answer 5

Subjects born and reared under either 19, 24 or 29 hour light/dark cycles

Then fed at a regular point in their own particular cycle and food delivery signalled a few hours before by a change in lighting

Animals on the 24 hour cycle learned to anticipate food but others didn’t

Question 6

What is the physiological basis of periodic timing?

Answer 6

Suprachiasmatic nucleus (SCN) of the hypothalamus is a candidate

The metabolic rate in the SCN appears to vary as a function of the day-night cycle

Lesions of the SCN abolish the circadian regularity of foraging and sleeping in the rat

Receives direct and indirect inputs from the visual system, which could keep circadian rhythms entrained with the real day-night cycle

Recent work suggests every cell in the body has a circadian rhythm, which are all under the control of the SCN

Question 7

What occurs with a disruption of circadian rhythms?

Answer 7

Responsible for physical illness

Associated with mental illness, such as depression, schizophrenia, bipolar illness

In Alzheimer’s disease the phenomenon of sundowning refers to the worsening of symptoms in afternoon/evening

Question 8

What is the peak procedure of interval timing?

Answer 8

• An animal is trained on a fixed-interval schedule
• The signal stays on longer than usual occasionally and no reward is given
• The animal keeps responding
• Response rates increase as the expected reward time approaches
• After the expected time passes, responding declines

Question 9

What was Church and Gibbon’s (1982) study?

Answer 9

• Rats in lit chamber
• Occasionally house light went off, for a 0.8, 4.0 or 7.2 sec (the CS)
• When the lights went on again a lever was
  presented for five seconds
• If the rat pressed the lever after a 4-sec CS it got food, otherwise it did not
• Then tested with a
  range of stimulus durations

Question 10

How does Weber’s law relate?

Answer 10

The just noticeable difference when you change a stimulus is proportional to the initial intensity/magnitude of the changed stimulus

In absolute terms small amounts judged more accurately than large amounts you can tell one from two sugars more easily than eight from nine

Question 11

How does Weber’s law apply to time?

Answer 11

The critical point is that percentage change is more important than absolute change

standard – comparison/standard

Reaches half maximum: 50% duration

Question 12

What is scalar timing theory?

Answer 12

Pacemaker > working memory > reference memory > comparator > response

• Pacemaker emits pulses at a roughly constant rate t
• When a stimulus is presented, a switch is operated , and the pulses are allowed to accumulate in working memory
• This will equal t multiplied by the number of second that have passed

Question 13

What is the storing duration of a stimulus in STM is scalar timing theory?

Answer 13

5 second stimulus: successive pulses stored in working memory

Question 14

What is storing duration of a stimulus in reference memory in scalar timing theory?

Answer 14

When reinforcement occurs, pulses stop accumulating; another switch allows the number of pulses in working memory to be stored in reference memory

This storage is not completely accurate – there is some memory distortion, this is represented by K, a number that is close to 1:

• If K = 1 the memory is accurate
• If K < 1 a smaller number of pulses is stored
• If K > 1 a greater number is stored

Question 15

How is error proportional to duration scalar?

Answer 15

After several trials there will be several numbers stored in reference memory

Question 16

How is stored value used in reference memory in deciding whether or not to respond on the next trial?

Answer 16

• Each trial the animal compares number of pulses in working memory with random value drawn from stored reference memory
• Done by the comparator, If the values are close, then the animal responds
• Another stimulus occurs, and successive number of pulses stored in working memory
• Animal uses one of the values in reference memory to decide when to respond
• The comparator works out how close the values are using a ratio rule – NOT a difference rule
• This is one of the reasons that accuracy is better with short intervals, scalar again

Question 17

What is process 3 in scalar timing theory?

Answer 17

Using stored value in reference memory to decide whether or not to respond on the next trial

Question 18

How is timing achieved by series of oscillators an alternative?

Answer 18

If each oscillator switches after a different
period of time, then the entire pattern of activation could be used to determine the exact time

Question 19

How is behavioural theory of timing an alternative?

Answer 19

• When the animal gets a reward, this stimulates behaviour.
• The animal moves across an invariant series of behavioural classes in between reinforcements
• A pulse from an internal pacemaker will change the behaviour from one class to another
• The behaviour that is occurring when the next
  reinforcer occurs becomes a signal for that reinforcer

Question 20

How are conditioning and timing occurring at the same time but controlled by different learning mechanisms?

Answer 20

• Some theories of timing try and explain conditioning
• Calculate rate of reinforcement during stimulus, and rate of reinforcement during background
• If rate of reinforcement in CS is higher than rate of reinforcement in background à conditioning