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Timing
• Periodic Timing– Cyclical behaviour controlled by 24 hour clock
time or (circadian)
• Interval Timing– Stopwatch timing
4pm 8pm Midnight 4am 8am Mid-day
ACTIVITY
Light off Light on
Periodic Timing
Controlled by daily time or by light off?
Roberts (1965)
• Activity cycle slightly less than 24 hours in constant dim light
• Restoring visual cues produces a gradual shift back to correct time.
• Entrainment: light acts as a zeitgeber (resets 24 hour clock)
Bolles & Stokes
24 hour19 hour 29 hour
“Just Right”“Too Hot” “Too Cold”
Bolles & Stokes (1965)
4am 8am Mid-day 4pm 8pm Midnight
Food
Light Dark
Periodic Timing
11pm 4am 8am Mid-day 4pm 8pm
Food
Light Dark
Paris
New York
Oscillators (Long Intervals)
Example
RRR RRG GGGGGRGRGGRRRGGRGR
432100
10
20
30
40
50
60
Adapted from Roberts (1982)
Five-second blocks
Mea
n re
spon
ses
per
min
ute
Interval Timing
Peak Procedure
141210864200
10
20
30
40
50
60
Five-second blocks
Mean r
esp
onse
s per
min
ute
One vs. Two Seconds
Absolute Difference = 1Weber’s Ratio = 1/2 = 0.5
Weber’s Law
Prediction: Very Easy
Nineteen vs. Twenty Seconds
Absolute Difference = 1Weber’s Ratio = 19/20 = 0.05
Weber’s Law
Prediction: Very Hard
Long or Short?
4 s
16 s
Choose Lever 1
Choose Lever 2
4 s
16 s10 s?
4 s
16 s8 s? 8 is twice 4
16 is twice 8
(16 + 4) * ½ = 10
Absolute
Ratio
((16)(4))1/2
=8
Temporal Discrimination
Absolute = (8+2) ½ = 5
Relative =((8)(2))1/2 = 4
BisectionTesting
Scalar Timing
• What scale is used to compare times?– Error is relative to stopwatch time
• error is a constant proportion of the timed interval
• called scalar timing
– Timing curves are identical if data are plotted as a function of the “percentage” of time remaining
• Step 1: Normalize Y-axis (common maximum)
• Step 2: X axis expressed as proportion of timed interval
Superposition
Scalar Timing
Learning-to-Time (LET)
BehaviorSequence: P M T L C
P = PeckM = MoveT = TurnL = LookC = Coo
Start Stop